SRCU changes for v4.19
cover SRCU changes for v4.19
Hello!
This series contains SRCU updates:
1. Fix typos in __call_srcu() comment header.
2. Document that srcu_funnel_gp_start() implies srcu_funnel_exp_start().
3. Add address of the first callback to rcutorture output to allow
this output to show (lack of) forward progress.
4. Introduce srcu_read_{un,}lock_notrace() to avoid lockdep issues
when applying SRCU to tracepoints.
Thanx, Paul
------------------------------------------------------------------------
include/linux/srcu.h | 17 +++++++++++++++++ kernel/rcu/srcutree.c | 26 +++++++++++++++----------- 2 files changed, 32 insertions(+), 11 deletions(-)
PATCH 1/4 srcu: Fix typos in __call_srcu() header comment
This commit simply changes some copy-pasta call_rcu() instances to the correct call_srcu().
--- kernel/rcu/srcutree.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
kernel/rcu/srcutree.c +4 -4
@@ -823,17 +823,17 @@ static void srcu_leak_callback(struct rcu_head *rhp)* more than one CPU, this means that when "func()" is invoked, each CPU * is guaranteed to have executed a full memory barrier since the end of * its last corresponding SRCU read-side critical section whose beginning -* preceded the call to call_rcu(). It also means that each CPU executing +* preceded the call to call_srcu(). It also means that each CPU executing * an SRCU read-side critical section that continues beyond the start of -* "func()" must have executed a memory barrier after the call_rcu() +* "func()" must have executed a memory barrier after the call_srcu() * but before the beginning of that SRCU read-side critical section. * Note that these guarantees include CPUs that are offline, idle, or * executing in user mode, as well as CPUs that are executing in the kernel. * -* Furthermore, if CPU A invoked call_rcu() and CPU B invoked the +* Furthermore, if CPU A invoked call_srcu() and CPU B invoked the * resulting SRCU callback function "func()", then both CPU A and CPU * B are guaranteed to execute a full memory barrier during the time -* interval between the call to call_rcu() and the invocation of "func()". +* interval between the call to call_srcu() and the invocation of "func()". * This guarantee applies even if CPU A and CPU B are the same CPU (but * again only if the system has more than one CPU). *
Signature · 1 line
2.17.1
Re: [PATCH tip/core/rcu 1/4] srcu: Fix typos in __call_srcu() header comment
Quoted 1 line · Paul E. McKenney
This commit simply changes some copy-pasta
call_rcu()instances to
^^^^^ cute :)
Quoted 6 lines
the correct
call_srcu().Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcu/srcutree.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
Signature · 1 line
~Randy
Re: [PATCH tip/core/rcu 1/4] srcu: Fix typos in __call_srcu() header comment
Quoted 4 lines · Randy Dunlap
Quoted 1 line · Paul E. McKenney
This commit simply changes some copy-pasta
call_rcu()instances to^^^^^ cute :)
Glad you like it! I was unable to determine if this copy-pasta constituted copy-spaghetti, copy-macaroni, copy-cannelloni, copy-rotelle, copy-linguini, copy-lasagne, or something else altogether.
You all can decide for yourselves. ;-)
Thanx, Paul
Quoted 11 lines
Quoted 6 lines
the correct
call_srcu().Signed-off-by Paul E. McKenney <[email protected]>--- kernel/rcu/srcutree.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)Signature · 1 line
~Randy
PATCH 2/4 srcu: Document that srcu_funnel_gp_start() implies srcu_funnel_exp_start()
In reply to Paul E. McKenneyThis commit updates the header comment of srcu_funnel_gp_start() to document the fact that srcu_funnel_gp_start() does the work of srcu_funnel_exp_start(), in some cases by invoking it directly.
--- kernel/rcu/srcutree.c | 3 +++ 1 file changed, 3 insertions(+)
kernel/rcu/srcutree.c +3 -0
@@ -641,6 +641,9 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp,* period s. Losers must either ensure that their desired grace-period * number is recorded on at least their leaf srcu_node structure, or they * must take steps to invoke their own callbacks. +* +* Note that this function also does the work of srcu_funnel_exp_start(), +* in some cases by directly invoking it. */ static void srcu_funnel_gp_start (struct srcu_struct *sp,struct srcu_data *sdp,unsigned long s,bool do_norm)
Signature · 1 line
2.17.1
PATCH 3/4 srcu: Add address of first callback to rcutorture output
In reply to Paul E. McKenneyThis commit adds the address of the first callback to the per-CPU rcutorture output in order to allow lost wakeups to be more efficiently tracked down.
--- kernel/rcu/srcutree.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
kernel/rcu/srcutree.c +8 -7
@@ -1271,11 +1271,11 @@ void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf)unsigned long l0, l1;unsigned long u0, u1;long c0, c1; -struct srcu_data *counts; +struct srcu_data *sdp; - counts =per_cpu_ptr (sp->sda, cpu); - u0 = counts->srcu_unlock_count[!idx]; - u1 = counts->srcu_unlock_count[idx]; + sdp =per_cpu_ptr (sp->sda, cpu); + u0 = sdp->srcu_unlock_count[!idx]; + u1 = sdp->srcu_unlock_count[idx];/* * Make sure that a lock is always counted if the corresponding
@@ -1283,12 +1283,13 @@ void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf)*/ smp_rmb (); - l0 = counts->srcu_lock_count[!idx]; - l1 = counts->srcu_lock_count[idx]; + l0 = sdp->srcu_lock_count[!idx]; + l1 = sdp->srcu_lock_count[idx]; c0 = l0 - u0; c1 = l1 - u1; -pr_cont (" %d(%ld,%ld)" , cpu, c0, c1); +pr_cont (" %d(%ld,%ld %1p)" , + cpu, c0, c1,rcu_segcblist_head (&sdp->srcu_cblist)); s0 += c0; s1 += c1; }
Signature · 1 line
2.17.1
PATCH 4/4 srcu: Introduce srcu_read_{un,}lock_notrace()
In reply to Paul E. McKenneyJoel Fernandes is using SRCU to protect from-idle tracepoints, which requires notrace variants of srcu_read_lock() and srcu_read_unlock() in order to avoid problems with tracepoints in lockdep. This commit therefore adds srcu_read_lock_notrace() and srcu_read_unlock_notrace().
[1] http://lkml.kernel.org/r/[email protected]
--- include/linux/srcu.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
include/linux/srcu.h +17 -0
@@ -195,6 +195,16 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)return retval; } +/* Used by tracing, cannot be traced and cannot invoke lockdep. */ +static inline notrace int +srcu_read_lock_notrace (struct srcu_struct *sp)__acquires (sp) +{ +int retval; + + retval =__srcu_read_lock (sp); +return retval; +} +/** * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. * @sp: srcu_struct in which to unregister the old reader.
@@ -209,6 +219,13 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)__srcu_read_unlock (sp, idx); } +/* Used by tracing, cannot be traced and cannot call lockdep. */ +static inline notrace void +srcu_read_unlock_notrace (struct srcu_struct *sp,int idx)__releases (sp) +{ +__srcu_read_unlock (sp, idx); +} +/** * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock *
Signature · 1 line
2.17.1