rcu: v2 patches queued for 2.6.35
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cover rcu: v2 patches queued for 2.6.35
Hello!
RFC preview of RCU patches queued for 2.6.35, take 2. Take 1 is at
http://lkml.org/lkml/2010/4/5/134. Changes to old patches noted in "[]", new patches flagged with "New".
1. substitute set_need_resched for sending resched IPIs
This reduces OS jitter.
2. make dead code really dead. [Updated commit message as suggested
by Mathieu Desnoyers.]
3. move some code from macro to function
Cleanups from Lai Jiangshan.
4. ignore offline CPUs in last non dyntick idle CPU check
Fix to my CONFIG_RCU_FAST_NO_HZ code to handle offline and non-existent CPUs, also from Lai Jiangshan.
5. fix bogus CONFIG_PROVE_LOCKING in comments to reality
6. fix now bogus rcu_scheduler_active comments
Comment fixups.
7. shrink rcutiny by making synchronize_rcu_bh be inline
Shrink TINY_RCU some more.
8. rename rcutiny rcu_ctrlblk to rcu_sched_ctrlblk
First step towards TINY_PREEMPTIBLE_RCU.
9. refactor RCU's context switch handling
Reduce the number of needless softirqs.
10. slim down rcutiny by removing rcu_scheduler_active and friends
More shrinkage for TINY_RCU
11. New: enable CPU_STALL_VERBOSE by default. It will have been in one
release, so time to enable it.
12. New: disable CPU stall warnings upon panic
13. New: print boot-time console messages if RCU configs out of ordinary
14. New: improve RCU CPU stall-warning messages
15. New: permit discontiguous cpu_possible_mask CPU numbering
16. New: v2: reduce the number of spurious RCU_SOFTIRQ invocations
Thanx, Paul
b/Documentation/RCU/trace.txt | 35 ++++++------ b/include/linux/rcupdate.h | 15 ++--- b/include/linux/rcutiny.h | 12 +++- b/include/linux/rcutree.h | 2 b/include/linux/srcu.h | 4 - b/kernel/rcupdate.c | 19 ------ b/kernel/rcutiny.c | 9 --- b/kernel/rcutiny_plugin.h | 39 +++++++++++++ b/kernel/rcutree.c | 10 +++ b/kernel/rcutree.h | 1 b/kernel/rcutree_plugin.h | 2 b/kernel/rcutree_trace.c | 4 + b/kernel/sched.c | 2 b/kernel/softirq.c | 2 b/lib/Kconfig.debug | 2 include/linux/rcupdate.h | 12 +--- include/linux/rcutiny.h | 17 +++++ include/linux/rcutree.h | 4 + kernel/rcutiny.c | 20 ++++-- kernel/rcutree.c | 121 +++++++++++++++++++++++++++++------------- kernel/rcutree.h | 1 kernel/rcutree_plugin.h | 55 +++++++++++++++++-- 22 files changed, 275 insertions(+), 113 deletions(-)
RFC PATCH 5/16 rcu: Fix bogus CONFIG_PROVE_LOCKING in comments to reflect reality.
It is CONFIG_DEBUG_LOCK_ALLOC rather than CONFIG_PROVE_LOCKING, so fix it.
--- include/linux/rcupdate.h | 15 ++++++++------- include/linux/srcu.h | 4 ++-- 2 files changed, 10 insertions(+), 9 deletions(-)
include/linux/rcupdate.h +8 -7
@@ -109,8 +109,8 @@ static inline int debug_lockdep_rcu_enabled(void)/** * rcu_read_lock_held - might we be in RCU read-side critical section? * -* If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in -* an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, +* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU +* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. *
@@ -132,11 +132,12 @@ extern int rcu_read_lock_bh_held(void);/** * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? * -* If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an -* RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING, -* this assumes we are in an RCU-sched read-side critical section unless it -* can prove otherwise. Note that disabling of preemption (including -* disabling irqs) counts as an RCU-sched read-side critical section. +* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an +* RCU-sched read-side critical section. In absence of +* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side +* critical section unless it can prove otherwise. Note that disabling +* of preemption (including disabling irqs) counts as an RCU-sched +* read-side critical section. * * Check rcu_scheduler_active to prevent false positives during boot. */
include/linux/srcu.h +2 -2
@@ -84,8 +84,8 @@ long srcu_batches_completed(struct srcu_struct *sp);/** * srcu_read_lock_held - might we be in SRCU read-side critical section? * -* If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in -* an SRCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, +* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU +* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an SRCU read-side critical section unless it can * prove otherwise. */
Signature · 1 line
1.7.0
RFC PATCH 2/16 rcu: make dead code really dead
In reply to Paul E. McKenneyFrom: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
kernel/rcutree.c +2 -2
@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ +raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ +/* Record dyntick-idle state. */ force_qs_rnp (rsp, dyntick_save_progress_counter);raw_spin_lock (&rnp->lock);/* irqs already disabled */
Signature · 1 line
1.7.0
RFC PATCH 1/16 rcu: substitute set_need_resched for sending resched IPIs
In reply to Paul E. McKenneyThis patch adds a check to __rcu_pending() that does a local set_need_resched() if the current CPU is holding up the current grace period and if force_quiescent_state() will be called soon. The goal is to reduce the probability that force_quiescent_state() will need to do smp_send_reschedule(), which sends an IPI and is therefore more expensive on most architectures.
--- kernel/rcutree.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-)
kernel/rcutree.c +10 -0
@@ -1499,6 +1499,16 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)/* Is the RCU core waiting for a quiescent state from this CPU? */ if (rdp->qs_pending) { + +/* +* If force_quiescent_state() coming soon and this CPU +* needs a quiescent state, and this is either RCU-sched +* or RCU-bh, force a local reschedule. +*/ +if (!rdp->preemptable && +ULONG_CMP_LT (ACCESS_ONCE (rsp->jiffies_force_qs) -1 , + jiffies)) +set_need_resched (); rdp->n_rp_qs_pending++;return 1 ; }
Signature · 1 line
1.7.0
RFC PATCH 15/16 rcu: permit discontiguous cpu_possible_mask CPU numbering
In reply to Paul E. McKenneyTREE_RCU assumes that CPU numbering is contiguous, but some users need large holes in the numbering to better map to hardware layout. This patch makes TREE_RCU (and TREE_PREEMPT_RCU) tolerate large holes in the CPU numbering. However, NR_CPUS must still be greater than the largest CPU number.
--- kernel/rcutree.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
kernel/rcutree.c +1 -1
@@ -1913,7 +1913,7 @@ static void __init rcu_init_one(struct rcu_state *rsp) rnp = rsp->level[NUM_RCU_LVLS -1 ];for_each_possible_cpu (i) { -if (i > rnp->grphi) +while (i > rnp->grphi) rnp++; rsp->rda[i]->mynode = rnp;rcu_boot_init_percpu_data (i, rsp);
Signature · 1 line
1.7.0
RFC PATCH 11/16 rcu: enable CPU_STALL_VERBOSE by default
In reply to Paul E. McKenneyThe CPU_STALL_VERBOSE kernel configuration parameter was added to 2.6.34 to identify any preempted/blocked tasks that were preventing the current grace period from completing when running preemptible RCU. As is conventional for new configurations parameters, this defaulted disabled. It is now time to enable it by default.
--- lib/Kconfig.debug | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
lib/Kconfig.debug +1 -1
@@ -792,7 +792,7 @@ config RCU_CPU_STALL_DETECTOR config RCU_CPU_STALL_VERBOSE bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU - default n + default y help This option causes RCU to printk detailed per-task information for any tasks that are stalling the current RCU grace period.
Signature · 1 line
1.7.0
RFC PATCH 6/16 rcu: fix now-bogus rcu_scheduler_active comments.
In reply to Paul E. McKenneyThe rcu_scheduler_active check has been wrapped into the new debug_lockdep_rcu_enabled() function, so update the comments to reflect this new reality.
--- include/linux/rcupdate.h | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-)
include/linux/rcupdate.h +4 -2
@@ -114,7 +114,8 @@ static inline int debug_lockdep_rcu_enabled(void)* this assumes we are in an RCU read-side critical section unless it can * prove otherwise. * -* Check rcu_scheduler_active to prevent false positives during boot. +* Check debug_lockdep_rcu_enabled() to prevent false positives during boot +* and while lockdep is disabled. */ static inline int rcu_read_lock_held (void ) {
@@ -139,7 +140,8 @@ extern int rcu_read_lock_bh_held(void);* of preemption (including disabling irqs) counts as an RCU-sched * read-side critical section. * -* Check rcu_scheduler_active to prevent false positives during boot. +* Check debug_lockdep_rcu_enabled() to prevent false positives during boot +* and while lockdep is disabled. */ #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held (void )
Signature · 1 line
1.7.0
RFC PATCH 10/16 rcu: slim down rcutiny by removing rcu_scheduler_active and friends
In reply to Paul E. McKenneyTINY_RCU does not need rcu_scheduler_active unless CONFIG_DEBUG_LOCK_ALLOC. So conditionally compile rcu_scheduler_active in order to slim down rcutiny a bit more. Also gets rid of an EXPORT_SYMBOL_GPL, which is responsible for most of the slimming.
--- include/linux/rcupdate.h | 4 +--- include/linux/rcutiny.h | 13 +++++++++++++ include/linux/rcutree.h | 3 +++ kernel/rcupdate.c | 19 ------------------- kernel/rcutiny.c | 7 +++++++ kernel/rcutiny_plugin.h | 39 +++++++++++++++++++++++++++++++++++++++ kernel/rcutree.c | 19 +++++++++++++++++++ 7 files changed, 82 insertions(+), 22 deletions(-) create mode 100644 kernel/rcutiny_plugin.h
include/linux/rcupdate.h +1 -3
@@ -64,8 +64,6 @@ extern int sched_expedited_torture_stats(char *page);/* Internal to kernel */ extern void rcu_init (void ); -extern int rcu_scheduler_active; -extern void rcu_scheduler_starting (void );#if defined(CONFIG_TREE_RCU ) || defined(CONFIG_TREE_PREEMPT_RCU )#include <linux/rcutree.h>
@@ -181,7 +179,7 @@ static inline int rcu_read_lock_bh_held(void)#ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held (void ) { -return !rcu_scheduler_active ||preempt_count () !=0 ||irqs_disabled (); +return preempt_count () !=0 ||irqs_disabled (); }#else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held (void )
include/linux/rcutiny.h +13 -0
@@ -128,4 +128,17 @@ static inline int rcu_preempt_depth(void) return 0; } +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +extern int rcu_scheduler_active__read_mostly ; +extern void rcu_scheduler_starting (void ); + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +static inline void rcu_scheduler_starting (void ) +{ +} + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ +#endif /* __LINUX_RCUTINY_H */
include/linux/rcutree.h +3 -0
@@ -123,4 +123,7 @@ static inline int rcu_blocking_is_gp(void) return num_online_cpus() == 1; } +extern void rcu_scheduler_starting (void ); +extern int rcu_scheduler_active__read_mostly ; +#endif /* __LINUX_RCUTREE_H */
kernel/rcupdate.c +0 -19
@@ -44,7 +44,6 @@#include <linux/cpu.h> #include <linux/mutex.h> #include <linux/module.h> -#include <linux/kernel_stat.h> #include <linux/hardirq.h> #ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -64,9 +63,6 @@ struct lockdep_map rcu_sched_lock_map =EXPORT_SYMBOL_GPL (rcu_sched_lock_map);#endif -int rcu_scheduler_active__read_mostly ; -EXPORT_SYMBOL_GPL (rcu_scheduler_active); -#ifdef CONFIG_DEBUG_LOCK_ALLOC /**
@@ -90,21 +86,6 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /* -* This function is invoked towards the end of the scheduler's initialization -* process. Before this is called, the idle task might contain -* RCU read-side critical sections (during which time, this idle -* task is booting the system). After this function is called, the -* idle tasks are prohibited from containing RCU read-side critical -* sections. -*/ -void rcu_scheduler_starting (void ) -{ -WARN_ON (num_online_cpus () !=1 ); -WARN_ON (nr_context_switches () >0 ); - rcu_scheduler_active =1 ; -} - -/* * Awaken the corresponding synchronize_rcu() instance now that a * grace period has elapsed. */
kernel/rcutiny.c +7 -0
@@ -54,6 +54,11 @@ static struct rcu_ctrlblk rcu_bh_ctrlblk = { .curtail = &rcu_bh_ctrlblk.rcucblist, }; +#ifdef CONFIG_DEBUG_LOCK_ALLOC +int rcu_scheduler_active__read_mostly ; +EXPORT_SYMBOL_GPL (rcu_scheduler_active); +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ +#ifdef CONFIG_NO_HZ static long rcu_dynticks_nesting =1 ;
@@ -276,3 +281,5 @@ void __init rcu_init(void) {open_softirq (RCU_SOFTIRQ , rcu_process_callbacks); } + +#include "rcutiny_plugin.h"
kernel/rcutiny_plugin.h new file +39 -0
@@ -0,0 +1,39 @@ +/* +* Read-Copy Update mechanism for mutual exclusion (tree-based version) +* Internal non-public definitions that provide either classic +* or preemptable semantics. +* +* This program is free software; you can redistribute it and/or modify +* it under the terms of the GNU General Public License as published by +* the Free Software Foundation; either version 2 of the License, or +* (at your option) any later version. +* +* This program is distributed in the hope that it will be useful, +* but WITHOUT ANY WARRANTY; without even the implied warranty of +* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +* GNU General Public License for more details. +* +* You should have received a copy of the GNU General Public License +* along with this program; if not, write to the Free Software +* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. +* +* Copyright IBM Corporation, 2009 +* +* Author: Paul E. McKenney <[email protected]> +*/ + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +#include <linux/kernel_stat.h> + +/* +* During boot, we forgive RCU lockdep issues. After this function is +* invoked, we start taking RCU lockdep issues seriously. +*/ +void rcu_scheduler_starting (void ) +{ +WARN_ON (nr_context_switches () >0 ); + rcu_scheduler_active =1 ; +} + +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
kernel/rcutree.c +19 -0
@@ -46,6 +46,7 @@#include <linux/cpu.h> #include <linux/mutex.h> #include <linux/time.h> +#include <linux/kernel_stat.h> #include "rcutree.h"
@@ -80,6 +81,9 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);struct rcu_state rcu_bh_state =RCU_STATE_INITIALIZER (rcu_bh_state); DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); +int rcu_scheduler_active__read_mostly ; +EXPORT_SYMBOL_GPL (rcu_scheduler_active); +/* * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s * permit this function to be invoked without holding the root rcu_node
@@ -1784,6 +1788,21 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, }/* +* This function is invoked towards the end of the scheduler's initialization +* process. Before this is called, the idle task might contain +* RCU read-side critical sections (during which time, this idle +* task is booting the system). After this function is called, the +* idle tasks are prohibited from containing RCU read-side critical +* sections. This function also enables RCU lockdep checking. +*/ +void rcu_scheduler_starting (void ) +{ +WARN_ON (num_online_cpus () !=1 ); +WARN_ON (nr_context_switches () >0 ); + rcu_scheduler_active =1 ; +} + +/* * Compute the per-level fanout, either using the exact fanout specified * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. */
Signature · 1 line
1.7.0
RFC PATCH 9/16 rcu: refactor RCU's context-switch handling
In reply to Paul E. McKenneyThe addition of preemptible RCU to treercu resulted in a bit of confusion and inefficiency surrounding the handling of context switches for RCU-sched and for RCU-preempt. For RCU-sched, a context switch is a quiescent state, pure and simple, just like it always has been. For RCU-preempt, a context switch is in no way a quiescent state, but special handling is required when a task blocks in an RCU read-side critical section.
However, the callout from the scheduler and the outer loop in ksoftirqd still calls something named rcu_sched_qs(), whose name is no longer accurate. Furthermore, when rcu_check_callbacks() notes an RCU-sched quiescent state, it ends up unnecessarily (though harmlessly, aside from the performance hit) enqueuing the current task if it happens to be running in an RCU-preempt read-side critical section. This not only increases the maximum latency of scheduler_tick(), it also needlessly increases the overhead of the next outermost rcu_read_unlock() invocation.
This patch addresses this situation by separating the notion of RCU's context-switch handling from that of RCU-sched's quiescent states. The context-switch handling is covered by rcu_note_context_switch() in general and by rcu_preempt_note_context_switch() for preemptible RCU. This permits rcu_sched_qs() to handle quiescent states and only quiescent states. It also reduces the maximum latency of scheduler_tick(), though probably by much less than a microsecond. Finally, it means that tasks within preemptible-RCU read-side critical sections avoid incurring the overhead of queuing unless there really is a context switch.
--- include/linux/rcutiny.h | 4 ++++ include/linux/rcutree.h | 1 + kernel/rcutree.c | 17 ++++++++++++----- kernel/rcutree_plugin.h | 11 +++++++---- kernel/sched.c | 2 +- kernel/softirq.c | 2 +- 6 files changed, 26 insertions(+), 11 deletions(-)
include/linux/rcutiny.h +4 -0
@@ -29,6 +29,10 @@void rcu_sched_qs (int cpu);void rcu_bh_qs (int cpu); +static inline void rcu_note_context_switch (int cpu) +{ +rcu_sched_qs (cpu); +}#define __rcu_read_lock () preempt_disable()#define __rcu_read_unlock () preempt_enable()
include/linux/rcutree.h +1 -0
@@ -34,6 +34,7 @@ struct notifier_block;extern void rcu_sched_qs (int cpu);extern void rcu_bh_qs (int cpu); +extern void rcu_note_context_switch (int cpu);extern int rcu_needs_cpu (int cpu);extern int rcu_expedited_torture_stats (char *page);
kernel/rcutree.c +12 -5
@@ -97,25 +97,32 @@ static int rcu_gp_in_progress(struct rcu_state *rsp)*/ void rcu_sched_qs (int cpu) { -struct rcu_data *rdp; +struct rcu_data *rdp = &per_cpu (rcu_sched_data, cpu); - rdp = &per_cpu (rcu_sched_data, cpu); rdp->passed_quiesc_completed = rdp->gpnum -1 ;barrier (); rdp->passed_quiesc =1 ; -rcu_preempt_note_context_switch (cpu); }void rcu_bh_qs (int cpu) { -struct rcu_data *rdp; +struct rcu_data *rdp = &per_cpu (rcu_bh_data, cpu); - rdp = &per_cpu (rcu_bh_data, cpu); rdp->passed_quiesc_completed = rdp->gpnum -1 ;barrier (); rdp->passed_quiesc =1 ; } +/* +* Note a context switch. This is a quiescent state for RCU-sched, +* and requires special handling for preemptible RCU. +*/ +void rcu_note_context_switch (int cpu) +{ +rcu_sched_qs (cpu); +rcu_preempt_note_context_switch (cpu); +} +#ifdef CONFIG_NO_HZ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { .dynticks_nesting = 1,
kernel/rcutree_plugin.h +7 -4
@@ -75,13 +75,19 @@ EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);* that this just means that the task currently running on the CPU is * not in a quiescent state. There might be any number of tasks blocked * while in an RCU read-side critical section. +* +* Unlike the other rcu_*_qs() functions, callers to this function +* must disable irqs in order to protect the assignment to +* ->rcu_read_unlock_special. */ static void rcu_preempt_qs (int cpu) {struct rcu_data *rdp = &per_cpu (rcu_preempt_data, cpu); + rdp->passed_quiesc_completed = rdp->gpnum -1 ;barrier (); rdp->passed_quiesc =1 ; + current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS ; }/*
@@ -144,9 +150,8 @@ static void rcu_preempt_note_context_switch(int cpu)* grace period, then the fact that the task has been enqueued * means that we continue to block the current grace period. */ -rcu_preempt_qs (cpu);local_irq_save (flags); - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS ; +rcu_preempt_qs (cpu);local_irq_restore (flags); }
@@ -236,7 +241,6 @@ static void rcu_read_unlock_special(struct task_struct *t)*/ special = t->rcu_read_unlock_special;if (special &RCU_READ_UNLOCK_NEED_QS ) { - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS ;rcu_preempt_qs (smp_processor_id ()); }
@@ -473,7 +477,6 @@ static void rcu_preempt_check_callbacks(int cpu)struct task_struct *t = current;if (t->rcu_read_lock_nesting ==0 ) { - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS ;rcu_preempt_qs (cpu);return ; }
kernel/sched.c +1 -1
@@ -3695,7 +3695,7 @@ need_resched:preempt_disable (); cpu =smp_processor_id (); rq =cpu_rq (cpu); -rcu_sched_qs (cpu); +rcu_note_context_switch (cpu); prev = rq->curr; switch_count = &prev->nivcsw;
kernel/softirq.c +1 -1
@@ -716,7 +716,7 @@ static int run_ksoftirqd(void * __bind_cpu)preempt_enable_no_resched ();cond_resched ();preempt_disable (); -rcu_sched_qs ((long )__bind_cpu); +rcu_note_context_switch ((long )__bind_cpu); }preempt_enable ();set_current_state (TASK_INTERRUPTIBLE );
Signature · 1 line
1.7.0
RFC PATCH 16/16 rcu: v2: reduce the number of spurious RCU_SOFTIRQ invocations
In reply to Paul E. McKenneyLai Jiangshan noted that up to 10% of the RCU_SOFTIRQ are spurious, and traced this down to the fact that the current grace-period machinery will uselessly raise RCU_SOFTIRQ when a given CPU needs to go through a quiescent state, but has not yet done so. In this situation, there might well be nothing that RCU_SOFTIRQ can do, and the overhead can be worth worrying about in the ksoftirqd case. This patch therefore avoids raising RCU_SOFTIRQ in this situation.
Changes since v1 (http://lkml.org/lkml/2010/3/30/122 from Lai Jiangshan):
o Omit the rcu_qs_pending() prechecks, as they aren't that
much less expensive than the quiescent-state checks.
o Merge with the set_need_resched() patch that reduces IPIs.
o Add the new n_rp_report_qs field to the rcu_pending tracing output.
o Update the tracing documentation accordingly.
--- Documentation/RCU/trace.txt | 35 +++++++++++++++++++---------------- kernel/rcutree.c | 11 ++++++----- kernel/rcutree.h | 1 + kernel/rcutree_trace.c | 4 +++- 4 files changed, 29 insertions(+), 22 deletions(-)
Documentation/RCU/trace.txt +19 -16
@@ -256,23 +256,23 @@ o Each element of the form "1/1 0:127 ^0" represents one struct The output of "cat rcu/rcu_pending" looks as follows: rcu_sched: - 0 np=255892 qsp=53936 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741 - 1 np=261224 qsp=54638 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792 - 2 np=237496 qsp=49664 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629 - 3 np=236249 qsp=48766 cbr=0 cng=286 gpc=48049 gps=1218 nf=207 nn=137723 - 4 np=221310 qsp=46850 cbr=0 cng=26 gpc=43161 gps=4634 nf=3529 nn=123110 - 5 np=237332 qsp=48449 cbr=0 cng=54 gpc=47920 gps=3252 nf=201 nn=137456 - 6 np=219995 qsp=46718 cbr=0 cng=50 gpc=42098 gps=6093 nf=4202 nn=120834 - 7 np=249893 qsp=49390 cbr=0 cng=72 gpc=38400 gps=17102 nf=41 nn=144888 + 0 np=255892 qsp=53936 rpq=85 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741 + 1 np=261224 qsp=54638 rpq=33 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792 + 2 np=237496 qsp=49664 rpq=23 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629 + 3 np=236249 qsp=48766 rpq=98 cbr=0 cng=286 gpc=48049 gps=1218 nf=207 nn=137723 + 4 np=221310 qsp=46850 rpq=7 cbr=0 cng=26 gpc=43161 gps=4634 nf=3529 nn=123110 + 5 np=237332 qsp=48449 rpq=9 cbr=0 cng=54 gpc=47920 gps=3252 nf=201 nn=137456 + 6 np=219995 qsp=46718 rpq=12 cbr=0 cng=50 gpc=42098 gps=6093 nf=4202 nn=120834 + 7 np=249893 qsp=49390 rpq=42 cbr=0 cng=72 gpc=38400 gps=17102 nf=41 nn=144888 rcu_bh: - 0 np=146741 qsp=1419 cbr=0 cng=6 gpc=0 gps=0 nf=2 nn=145314 - 1 np=155792 qsp=12597 cbr=0 cng=0 gpc=4 gps=8 nf=3 nn=143180 - 2 np=136629 qsp=18680 cbr=0 cng=0 gpc=7 gps=6 nf=0 nn=117936 - 3 np=137723 qsp=2843 cbr=0 cng=0 gpc=10 gps=7 nf=0 nn=134863 - 4 np=123110 qsp=12433 cbr=0 cng=0 gpc=4 gps=2 nf=0 nn=110671 - 5 np=137456 qsp=4210 cbr=0 cng=0 gpc=6 gps=5 nf=0 nn=133235 - 6 np=120834 qsp=9902 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921 - 7 np=144888 qsp=26336 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542 + 0 np=146741 qsp=1419 rpq=6 cbr=0 cng=6 gpc=0 gps=0 nf=2 nn=145314 + 1 np=155792 qsp=12597 rpq=3 cbr=0 cng=0 gpc=4 gps=8 nf=3 nn=143180 + 2 np=136629 qsp=18680 rpq=1 cbr=0 cng=0 gpc=7 gps=6 nf=0 nn=117936 + 3 np=137723 qsp=2843 rpq=0 cbr=0 cng=0 gpc=10 gps=7 nf=0 nn=134863 + 4 np=123110 qsp=12433 rpq=0 cbr=0 cng=0 gpc=4 gps=2 nf=0 nn=110671 + 5 np=137456 qsp=4210 rpq=1 cbr=0 cng=0 gpc=6 gps=5 nf=0 nn=133235 + 6 np=120834 qsp=9902 rpq=2 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921 + 7 np=144888 qsp=26336 rpq=0 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542 As always, this is once again split into "rcu_sched" and "rcu_bh" portions, with CONFIG_TREE_PREEMPT_RCU kernels having an additional
@@ -284,6 +284,9 @@ o "np" is the number of times that __rcu_pending() has been invoked o "qsp" is the number of times that the RCU was waiting for a quiescent state from this CPU. +o "rpq" is the number of times that the CPU had passed through + a quiescent state, but not yet reported it to RCU. + o "cbr" is the number of times that this CPU had RCU callbacks that had passed through a grace period, and were thus ready to be invoked.
kernel/rcutree.c +6 -5
@@ -1161,8 +1161,6 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)*/ void rcu_check_callbacks (int cpu,int user) { -if (!rcu_pending (cpu)) -return ;/* if nothing for RCU to do. */ if (user || (idle_cpu (cpu) && rcu_scheduler_active && !in_softirq () &&hardirq_count () <= (1 <<HARDIRQ_SHIFT ))) {
@@ -1194,7 +1192,8 @@ void rcu_check_callbacks(int cpu, int user)rcu_bh_qs (cpu); }rcu_preempt_check_callbacks (cpu); -raise_softirq (RCU_SOFTIRQ ); +if (rcu_pending (cpu)) +raise_softirq (RCU_SOFTIRQ ); }#ifdef CONFIG_SMP
@@ -1534,18 +1533,20 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)check_cpu_stall (rsp, rdp);/* Is the RCU core waiting for a quiescent state from this CPU? */ -if (rdp->qs_pending) { +if (rdp->qs_pending && !rdp->passed_quiesc) {/* * If force_quiescent_state() coming soon and this CPU * needs a quiescent state, and this is either RCU-sched * or RCU-bh, force a local reschedule. */ + rdp->n_rp_qs_pending++;if (!rdp->preemptable &&ULONG_CMP_LT (ACCESS_ONCE (rsp->jiffies_force_qs) -1 , jiffies))set_need_resched (); - rdp->n_rp_qs_pending++; + }else if (rdp->qs_pending && rdp->passed_quiesc) { + rdp->n_rp_report_qs++;return 1 ; }
kernel/rcutree.h +1 -0
@@ -223,6 +223,7 @@ struct rcu_data {/* 5) __rcu_pending() statistics. */ unsigned long n_rcu_pending;/* rcu_pending() calls since boot. */ unsigned long n_rp_qs_pending; +unsigned long n_rp_report_qs;unsigned long n_rp_cb_ready;unsigned long n_rp_cpu_needs_gp;unsigned long n_rp_gp_completed;
kernel/rcutree_trace.c +3 -1
@@ -241,11 +241,13 @@ static const struct file_operations rcugp_fops = {static void print_one_rcu_pending (struct seq_file *m,struct rcu_data *rdp) { seq_printf(m, "%3d%cnp=%ld " - "qsp=%ld cbr=%ld cng=%ld gpc=%ld gps=%ld nf=%ld nn=%ld\n", + "qsp=%ld rpq=%ld cbr=%ld cng=%ld " + "gpc=%ld gps=%ld nf=%ld nn=%ld\n", rdp->cpu, cpu_is_offline(rdp->cpu) ? '!' : ' ', rdp->n_rcu_pending, rdp->n_rp_qs_pending, + rdp->n_rp_report_qs, rdp->n_rp_cb_ready, rdp->n_rp_cpu_needs_gp, rdp->n_rp_gp_completed,
Signature · 1 line
1.7.0
RFC PATCH 7/16 rcu: shrink rcutiny by making synchronize_rcu_bh() be inline
In reply to Paul E. McKenneyBecause synchronize_rcu_bh() is identical to synchronize_sched(), make the former a static inline invoking the latter, saving the overhead of an EXPORT_SYMBOL_GPL() and the duplicate code.
--- include/linux/rcupdate.h | 2 -- include/linux/rcutiny.h | 12 +++++++++++- include/linux/rcutree.h | 2 ++ kernel/rcutiny.c | 9 ++------- 4 files changed, 15 insertions(+), 10 deletions(-)
include/linux/rcupdate.h +0 -2
@@ -56,8 +56,6 @@ struct rcu_head { };/* Exported common interfaces */ -extern void synchronize_rcu_bh (void ); -extern void synchronize_sched (void );extern void rcu_barrier (void );extern void rcu_barrier_bh (void );extern void rcu_barrier_sched (void );
include/linux/rcutiny.h +11 -1
@@ -74,7 +74,17 @@ static inline void rcu_sched_force_quiescent_state(void) { } -#define synchronize_rcu synchronize_sched +extern void synchronize_sched (void ); + +static inline void synchronize_rcu (void ) +{ +synchronize_sched (); +} + +static inline void synchronize_rcu_bh (void ) +{ +synchronize_sched (); +}static inline void synchronize_rcu_expedited (void ) {
include/linux/rcutree.h +2 -0
@@ -86,6 +86,8 @@ static inline void __rcu_read_unlock_bh(void)extern void call_rcu_sched (struct rcu_head *head,void (*func)(struct rcu_head *rcu)); +extern void synchronize_rcu_bh (void ); +extern void synchronize_sched (void );extern void synchronize_rcu_expedited (void );static inline void synchronize_rcu_bh_expedited (void )
kernel/rcutiny.c +2 -7
@@ -187,7 +187,8 @@ static void rcu_process_callbacks(struct softirq_action *unused)* * Cool, huh? (Due to Josh Triplett.) * -* But we want to make this a static inline later. +* But we want to make this a static inline later. The cond_resched() +* currently makes this problematic. */ void synchronize_sched (void ) {
@@ -195,12 +196,6 @@ void synchronize_sched(void) }EXPORT_SYMBOL_GPL (synchronize_sched); -void synchronize_rcu_bh (void ) -{ -synchronize_sched (); -} -EXPORT_SYMBOL_GPL (synchronize_rcu_bh); -/* * Helper function for call_rcu() and call_rcu_bh(). */
Signature · 1 line
1.7.0
RFC PATCH 8/16 rcu: rename rcutiny rcu_ctrlblk to rcu_sched_ctrlblk
In reply to Paul E. McKenneyMake naming line up in preparation for CONFIG_TINY_PREEMPT_RCU.
--- kernel/rcutiny.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-)
kernel/rcutiny.c +7 -6
@@ -44,9 +44,9 @@ struct rcu_ctrlblk { };/* Definition for rcupdate control block. */ -static struct rcu_ctrlblk rcu_ctrlblk = { - .donetail = &rcu_ctrlblk.rcucblist, - .curtail = &rcu_ctrlblk.rcucblist, +static struct rcu_ctrlblk rcu_sched_ctrlblk = { + .donetail = &rcu_sched_ctrlblk.rcucblist, + .curtail = &rcu_sched_ctrlblk.rcucblist, };static struct rcu_ctrlblk rcu_bh_ctrlblk = {
@@ -108,7 +108,8 @@ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)*/ void rcu_sched_qs (int cpu) { -if (rcu_qsctr_help (&rcu_ctrlblk) +rcu_qsctr_help (&rcu_bh_ctrlblk)) +if (rcu_qsctr_help (&rcu_sched_ctrlblk) + +rcu_qsctr_help (&rcu_bh_ctrlblk))raise_softirq (RCU_SOFTIRQ ); }
@@ -173,7 +174,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)*/ static void rcu_process_callbacks (struct softirq_action *unused) { -__rcu_process_callbacks (&rcu_ctrlblk); +__rcu_process_callbacks (&rcu_sched_ctrlblk);__rcu_process_callbacks (&rcu_bh_ctrlblk); }
@@ -221,7 +222,7 @@ static void __call_rcu(struct rcu_head *head,*/ void call_rcu (struct rcu_head *head,void (*func)(struct rcu_head *rcu)) { -__call_rcu (head, func, &rcu_ctrlblk); +__call_rcu (head, func, &rcu_sched_ctrlblk); }EXPORT_SYMBOL_GPL (call_rcu);
Signature · 1 line
1.7.0
RFC PATCH 14/16 rcu: improve RCU CPU stall-warning messages
In reply to Paul E. McKenneyThe existing RCU CPU stall-warning messages can be confusing, especially in the case where one CPU detects a single other stalled CPU. In addition, the console messages did not say which flavor of RCU detected the stall, which can make it difficult to work out exactly what is causing the stall. This commit improves these messages.
--- kernel/rcutree.c | 20 +++++++++++--------- kernel/rcutree.h | 1 + 2 files changed, 12 insertions(+), 9 deletions(-)
kernel/rcutree.c +11 -9
@@ -54,8 +54,8 @@static struct lock_class_key rcu_node_class[NUM_RCU_LVLS ]; -#define RCU_STATE_INITIALIZER(name) { \ - .level = { &name.node[0] }, \ +#define RCU_STATE_INITIALIZER(structname) { \ + .level = { &structname.node[0] }, \ .levelcnt = { \ NUM_RCU_LVL_0, /* root of hierarchy. */ \NUM_RCU_LVL_1 , \
@@ -66,13 +66,14 @@ static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; .signaled = RCU_GP_IDLE, \ .gpnum = -300, \ .completed = -300, \ - .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&name.onofflock), \ + .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \ .orphan_cbs_list = NULL, \ - .orphan_cbs_tail = &name.orphan_cbs_list, \ + .orphan_cbs_tail = &structname.orphan_cbs_list, \ .orphan_qlen = 0, \ - .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&name.fqslock), \ + .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \ .n_force_qs = 0, \ .n_force_qs_ngp = 0, \ + .name = #structname, \ }struct rcu_state rcu_sched_state =RCU_STATE_INITIALIZER (rcu_sched_state);
@@ -483,7 +484,8 @@ static void print_other_cpu_stall(struct rcu_state *rsp)/* OK, time to rat on our buddy... */ -printk (KERN_ERR "INFO: RCU detected CPU stalls:" ); +printk (KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {" , + rsp->name);rcu_for_each_leaf_node (rsp, rnp) {raw_spin_lock_irqsave (&rnp->lock, flags);rcu_print_task_stall (rnp);
@@ -494,7 +496,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)if (rnp->qsmask & (1UL << cpu))printk (" %d" , rnp->grplo + cpu); } -printk (" (detected by %d, t=%ld jiffies)\n" , +printk ("} (detected by %d, t=%ld jiffies)\n" ,smp_processor_id (), (long )(jiffies - rsp->gp_start));trigger_all_cpu_backtrace ();
@@ -510,8 +512,8 @@ static void print_cpu_stall(struct rcu_state *rsp)unsigned long flags;struct rcu_node *rnp =rcu_get_root (rsp); -printk (KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n" , -smp_processor_id (), jiffies - rsp->gp_start); +printk (KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n" , + rsp->name,smp_processor_id (), jiffies - rsp->gp_start);trigger_all_cpu_backtrace ();raw_spin_lock_irqsave (&rnp->lock, flags);
kernel/rcutree.h +1 -0
@@ -326,6 +326,7 @@ struct rcu_state {unsigned long jiffies_stall;/* Time at which to check */ /* for CPU stalls. */ #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ +char *name;/* Name of structure. */ };/* Return values for rcu_preempt_offline_tasks(). */
Signature · 1 line
1.7.0
RFC PATCH 3/16 rcu: move some code from macro to function
In reply to Paul E. McKenneyFrom: Lai Jiangshan <[email protected]>
Shrink the RCU_INIT_FLAVOR() macro by moving all but the initialization of the ->rda[] array to rcu_init_one(). The call to rcu_init_one() can then be moved to the end of the RCU_INIT_FLAVOR() macro, which is required because rcu_boot_init_percpu_data(), which is now called from rcu_init_one(), depends on the initialization of the ->rda[] array.
--- kernel/rcutree.c | 18 +++++++++--------- 1 files changed, 9 insertions(+), 9 deletions(-)
kernel/rcutree.c +9 -9
@@ -1859,6 +1859,14 @@ static void __init rcu_init_one(struct rcu_state *rsp)INIT_LIST_HEAD (&rnp->blocked_tasks[3 ]); } } + + rnp = rsp->level[NUM_RCU_LVLS -1 ]; +for_each_possible_cpu (i) { +if (i > rnp->grphi) + rnp++; + rsp->rda[i]->mynode = rnp; +rcu_boot_init_percpu_data (i, rsp); + } }/*
@@ -1869,19 +1877,11 @@ static void __init rcu_init_one(struct rcu_state *rsp)#define RCU_INIT_FLAVOR (rsp, rcu_data) \ do { \ int i; \ - int j; \ - struct rcu_node *rnp; \ \ - rcu_init_one(rsp); \ - rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ - j = 0; \ for_each_possible_cpu(i) { \ - if (i > rnp[j].grphi) \ - j++; \ - per_cpu(rcu_data, i).mynode = &rnp[j]; \ (rsp)->rda[i] = &per_cpu(rcu_data, i); \ - rcu_boot_init_percpu_data(i, rsp); \ } \ + rcu_init_one(rsp); \ } while (0)void __init rcu_init (void )
Signature · 1 line
1.7.0
RFC PATCH 12/16 rcu: disable CPU stall warnings upon panic
In reply to Paul E. McKenneyThe current RCU CPU stall warnings remain enabled even after a panic occurs, which some people have found to be a bit counterproductive. This patch therefore uses a notifier to disable stall warnings once a panic occurs.
--- kernel/rcutree.c | 24 ++++++++++++++++++++++++ 1 files changed, 24 insertions(+), 0 deletions(-)
kernel/rcutree.c +24 -0
@@ -449,6 +449,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)#ifdef CONFIG_RCU_CPU_STALL_DETECTOR +int rcu_cpu_stall_panicking__read_mostly ; +static void record_gp_stall_check_time (struct rcu_state *rsp) { rsp->gp_start = jiffies;
@@ -526,6 +528,8 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)long delta;struct rcu_node *rnp; +if (rcu_cpu_stall_panicking) +return ; delta = jiffies - rsp->jiffies_stall; rnp = rdp->mynode;if ((rnp->qsmask & rdp->grpmask) && delta >=0 ) {
@@ -540,6 +544,21 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) } } +static int rcu_panic (struct notifier_block *this,unsigned long ev,void *ptr) +{ + rcu_cpu_stall_panicking =1 ; +return NOTIFY_DONE ; +} + +static struct notifier_block rcu_panic_block = { + .notifier_call = rcu_panic, +}; + +static void __init check_cpu_stall_init (void ) +{ +atomic_notifier_chain_register (&panic_notifier_list, &rcu_panic_block); +} +#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ static void record_gp_stall_check_time (struct rcu_state *rsp)
@@ -550,6 +569,10 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) { } +static void __init check_cpu_stall_init (void ) +{ +} +#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ /*
@@ -1934,6 +1957,7 @@ void __init rcu_init(void)cpu_notifier (rcu_cpu_notify,0 );for_each_online_cpu (cpu)rcu_cpu_notify (NULL ,CPU_UP_PREPARE , (void *)(long )cpu); +check_cpu_stall_init (); }#include "rcutree_plugin.h"
Signature · 1 line
1.7.0
RFC PATCH 13/16 rcu: print boot-time console messages if RCU configs out of ordinary
In reply to Paul E. McKenneyPrint boot-time messages if tracing is enabled, if fanout is set to non-default values, if exact fanout is specified, if accelerated dyntick-idle grace periods have been enabled, if RCU-lockdep is enabled, if rcutorture has been boot-time enabled, if the CPU stall detector has been disabled, or if four-level hierarchy has been enabled.
This is all for TREE_RCU and TREE_PREEMPT_RCU. TINY_RCU will be handled separately, if at all.
--- kernel/rcutree.c | 6 ------ kernel/rcutree_plugin.h | 44 ++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 42 insertions(+), 8 deletions(-)
kernel/rcutree.c +0 -6
@@ -1938,12 +1938,6 @@ void __init rcu_init(void)int cpu;rcu_bootup_announce (); -#ifdef CONFIG_RCU_CPU_STALL_DETECTOR -printk (KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n" ); -#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ -#if NUM_RCU_LVL_4 !=0 -printk (KERN_INFO "Experimental four-level hierarchy is enabled.\n" ); -#endif /* #if NUM_RCU_LVL_4 != 0 */ RCU_INIT_FLAVOR (&rcu_sched_state, rcu_sched_data);RCU_INIT_FLAVOR (&rcu_bh_state, rcu_bh_data);__rcu_init_preempt ();
kernel/rcutree_plugin.h +42 -2
62 lines not on this page · raw message
Signature · 1 line
1.7.0
RFC PATCH 4/16 rcu: ignore offline CPUs in last non-dyntick-idle CPU check
In reply to Paul E. McKenneyFrom: Lai Jiangshan <[email protected]>
Offline CPUs are not in nohz_cpu_mask, but can be ignored when checking for the last non-dyntick-idle CPU. This patch therefore only checks online CPUs for not being dyntick idle, allowing fast entry into full-system dyntick-idle state even when there are some offline CPUs.
--- kernel/rcutree_plugin.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
kernel/rcutree_plugin.h +1 -1
@@ -1016,7 +1016,7 @@ int rcu_needs_cpu(int cpu)/* Don't bother unless we are the last non-dyntick-idle CPU. */ for_each_cpu_not (thatcpu, nohz_cpu_mask) -if (thatcpu != cpu) { +if (cpu_online (thatcpu) && thatcpu != cpu) {per_cpu (rcu_dyntick_drain, cpu) =0 ;per_cpu (rcu_dyntick_holdoff, cpu) = jiffies -1 ;return rcu_needs_cpu_quick_check (cpu);
Signature · 1 line
1.7.0
Josh Triplett
maintainerRe: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
In reply to Paul E. McKenneyQuoted 15 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 7 lines
kernel/rcutree.c +0
-2@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */
GCC's new __builtin_unreachable would help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper in compiler.h would let us use it when available though.
- Josh Triplett
Re: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */
Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);
But this is beginning to seem a bit strained to me. ;-)
Thanx, Paul
Josh Triplett
maintainerRe: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.
Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();
Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) {
unreachable();
break;
}But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
- Josh Triplett
Re: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 48 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
Quoted 7 lines
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
Thanx, Paul
Josh Triplett
maintainerRe: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 54 lines · Paul E. McKenney
Quoted 53 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }
Quoted 5 lines
Quoted 2 lines
But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
I just meant that those constants get #defined based on CONFIG_NO_HZ, so an #ifdef on that would remove the need for the special handling of dead code.
- Josh Triplett
Re: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 58 lines · Josh Triplett
Quoted 57 lines · Paul E. McKenney
Quoted 55 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Quoted 6 lines
Quoted 2 lines
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
I just meant that those constants get #defined based on
CONFIG_NO_HZ, so an #ifdef on that would remove the need for the special handling of dead code.
True, I could put a #ifdef CONFIG_NO_HZ around that leg of the switch statement. Or am I still missing your point?
Thanx, Paul
Josh Triplett
maintainerRe: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 62 lines · Paul E. McKenney
Quoted 61 lines · Josh Triplett
Quoted 59 lines · Paul E. McKenney
Quoted 48 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
Quoted 7 lines
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
Quoted 6 lines
Quoted 3 lines
I just meant that those constants get #defined based on
CONFIG_NO_HZ, so an #ifdef on that would remove the need for the special handling of dead code.True, I could put a #ifdef
CONFIG_NO_HZaround that leg of the switch statement. Or am I still missing your point?
No, you got it exactly. Hence my suggesting that all the other alternatives (the if with a break, or with __builtin_unreachable) seemed excessive just to try to convince the compiler to infer what an ifdef would tell it explicitly. :)
- Josh Triplett
Re: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 67 lines · Josh Triplett
Quoted 66 lines · Paul E. McKenney
Quoted 64 lines · Josh Triplett
Quoted 54 lines · Paul E. McKenney
Quoted 53 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }Quoted 5 lines
Quoted 2 lines
But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
I just meant that those constants get #defined based on
CONFIG_NO_HZ, so an #ifdef on that would remove the need for the special handling of dead code.
Quoted 7 lines
Quoted 2 lines
True, I could put a #ifdef
CONFIG_NO_HZaround that leg of the switch statement. Or am I still missing your point?No, you got it exactly. Hence my suggesting that all the other alternatives (the if with a break, or with
__builtin_unreachable) seemed excessive just to try to convince the compiler to infer what an ifdef would tell it explicitly. :)
Which is exactly the purpose of the "if" statement comparing the two constants, right? ;-)
Thanx, Paul
Josh Triplett
maintainerRe: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 71 lines · Paul E. McKenney
Quoted 70 lines · Josh Triplett
Quoted 68 lines · Paul E. McKenney
Quoted 58 lines · Josh Triplett
Quoted 57 lines · Paul E. McKenney
Quoted 55 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Quoted 6 lines
Quoted 2 lines
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
I just meant that those constants get #defined based on
CONFIG_NO_HZ, so an #ifdef on that would remove the need for the special handling of dead code.True, I could put a #ifdef
CONFIG_NO_HZaround that leg of the switch statement. Or am I still missing your point?
Quoted 7 lines
Quoted 4 lines
No, you got it exactly. Hence my suggesting that all the other alternatives (the if with a break, or with
__builtin_unreachable) seemed excessive just to try to convince the compiler to infer what an ifdef would tell it explicitly. :)Which is exactly the purpose of the "if" statement comparing the two constants, right? ;-)
Right, which also seems excessive compared to an ifdef, since it serves the same purpose but more confusingly. ;)
- Josh Triplett
Re: [PATCH RFC tip/core/rcu 02/16] rcu: make dead code really dead
Quoted 77 lines · Josh Triplett
Quoted 76 lines · Paul E. McKenney
Quoted 74 lines · Josh Triplett
Quoted 62 lines · Paul E. McKenney
Quoted 61 lines · Josh Triplett
Quoted 59 lines · Paul E. McKenney
Quoted 48 lines · Josh Triplett
Quoted 29 lines · Paul E. McKenney
Quoted 18 lines · Josh Triplett
Quoted 17 lines · Paul E. McKenney
From: Lai Jiangshan <[email protected]>
cleanup: make dead code really dead
Signed-off-by Lai Jiangshan <[email protected]>Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)kernel/rcutree.c +0
-0@@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)break ;/* grace period idle or initializing, ignore. */ Quoted 9 lines
kernel/rcutree.c static void force_quiescent_state(struct rcu_state *rsp, int relaxed) · line 1240
Quoted 5 lines
kernel/rcutree.c +0
-2case RCU_SAVE_DYNTICK : - -raw_spin_unlock (&rnp->lock);/* irqs remain disabled */ if (RCU_SIGNAL_INIT !=RCU_SAVE_DYNTICK )break ;/* So gcc recognizes the dead code. */ GCC's new
__builtin_unreachablewould help here, though obviously we can't count on 4.5 or newer quite yet. A wrapper incompiler.hwould let us use it when available though.Quoted 5 lines
So at some time when we can count on gcc 4.5 or newer, the code would look something like the following?
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable();Yes, exactly.
Quoted 7 lines
I suppose that in the meantime one could supply the code to use in the unreachable case:
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) this_is_unreachable(break);But this is beginning to seem a bit strained to me. ;-)
I'd suggest spelling that this way:
Quoted 7 lines
if (RCU_SIGNAL_INIT == RCU_SAVE_DYNTICK) { unreachable(); break; }But in any case, all of these do seem excessive just to avoid the need for an ifdef. :)
Actually, the "if" condition is a comparison of numerical constants, so no #ifdef is required.
Quoted 6 lines
Quoted 3 lines
I just meant that those constants get #defined based on
CONFIG_NO_HZ, so an #ifdef on that would remove the need for the special handling of dead code.True, I could put a #ifdef
CONFIG_NO_HZaround that leg of the switch statement. Or am I still missing your point?No, you got it exactly. Hence my suggesting that all the other alternatives (the if with a break, or with
__builtin_unreachable) seemed excessive just to try to convince the compiler to infer what an ifdef would tell it explicitly. :)
Quoted 5 lines
Quoted 2 lines
Which is exactly the purpose of the "if" statement comparing the two constants, right? ;-)
Right, which also seems excessive compared to an ifdef, since it serves the same purpose but more confusingly. ;)
Well, I must confess that it confused me when I added the spin_unlock()...
Thanx, Paul
Re: [PATCH RFC tip/core/rcu 07/16] rcu: shrink rcutiny by making synchronize_rcu_bh() be inline
In reply to Paul E. McKenneyDoes it make sense for synchronize_sched() to be inline too? Since that's just a wrapper around cond_resched(), which is normally just a wrapper around _cond_resched().
Otherwise:
Re: [PATCH RFC tip/core/rcu 10/16] rcu: slim down rcutiny by removing rcu_scheduler_active and friends
In reply to Paul E. McKenneykernel/rcutiny_plugin.h line 37
Quoted 5 lines · Paul E. McKenney
kernel/rcutiny_plugin.h new file +5
-0+void rcu_scheduler_starting (void ) +{ +WARN_ON (nr_context_switches () >0 ); + rcu_scheduler_active =1 ; +}
Since rcu_scheduler_active is a global variable, does it make sense to make this an inline function in the header file?
It looks decidedly odd in its own include file as you've done it. Wouldn't the right way to do this be to split it into its own .c file and conditionally compile it in the Makefile?
David
Re: [PATCH RFC tip/core/rcu 07/16] rcu: shrink rcutiny by making synchronize_rcu_bh() be inline
In reply to David HowellsQuoted 4 lines · David Howells
Does it make sense for
synchronize_sched()to be inline too? Since that's just a wrapper aroundcond_resched(), which is normally just a wrapper around_cond_resched().
I tried that, and quickly descended into #include hell. :-(
Thanx, Paul
Quoted 3 lines
Otherwise:
Acked-by David Howells <[email protected]>
Re: [PATCH RFC tip/core/rcu 10/16] rcu: slim down rcutiny by removing rcu_scheduler_active and friends
In reply to David HowellsQuoted 10 lines · David Howells
kernel/rcutiny_plugin.h line 37
Quoted 5 lines · Paul E. McKenney
kernel/rcutiny_plugin.h new file +5
-0+void rcu_scheduler_starting (void ) +{ +WARN_ON (nr_context_switches () >0 ); + rcu_scheduler_active =1 ; +}Since
rcu_scheduler_activeis a global variable, does it make sense to make this an inline function in the header file?
Unfortunately, nr_context_switches() put me in #include hell when I tried that.
Quoted 3 lines
It looks decidedly odd in its own include file as you've done it. Wouldn't the right way to do this be to split it into its own .c file and conditionally compile it in the
Makefile?
It will soon have lots of company, as this is where the plugins for CONFIG_TINY_PREEMPT_RCU will go. In other words, kernel/rcutiny.c will have the same relationship to kernel/rcutiny_plugin.h that kernel/rcutree.c has with kernel/rcutree_plugin.h.
Thanx, Paul