Linux 3.10.97-rt106-rc1

---
 arch/arm/kernel/smp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

arch/arm/kernel/smp.c +3 -2

index 5919eb451bb9..7ad24aa57040 100644
@@ -192,8 +192,6 @@ int __cpuinit __cpu_disable(void)
 	flush_cache_louis();
 	local_flush_tlb_all();
 
-	clear_tasks_mm_cpumask(cpu);
-
 	return 0;
 }

@@ -209,6 +207,9 @@ void __cpuinit __cpu_die(unsigned int cpu)
 		pr_err("CPU%u: cpu didn't die\n", cpu);
 		return;
 	}
+
+	clear_tasks_mm_cpumask(cpu);
+
 	printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
 
 	/*

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #2 lore raw

PATCH 2/10 rtmutex: Handle non enqueued waiters gracefully

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <[email protected]>

Yimin debugged that in case of a PI wakeup in progress when rt_mutex_start_proxy_lock() calls task_blocks_on_rt_mutex() the latter returns -EAGAIN and in consequence the remove_waiter() call runs into a BUG_ON() because there is nothing to remove.

Guard it with rt_mutex_has_waiters(). This is a quick fix which is easy to backport. The proper fix is to have a central check in remove_waiter() so we can call it unconditionally.

Reported-and-debugged-by Yimin Deng <[email protected]>

---
 kernel/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

kernel/rtmutex.c +1 -1

index 5388ba98acaf..3f169f882775 100644
@@ -1914,7 +1914,7 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 		ret = 0;
 	}
 
-	if (unlikely(ret))
+	if (ret && rt_mutex_has_waiters(lock))
 		remove_waiter(lock, waiter);
 
 	raw_spin_unlock(&lock->wait_lock);

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 22:20 UTC #3 lore raw

PATCH 3/10 rtmutex: Use chainwalking control enum

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "[email protected]" <[email protected]>

In 8930ed80 (rtmutex: Cleanup deadlock detector debug logic), chainwalking control enums were introduced to limit the deadlock detection logic. One of the calls to task_blocks_on_rt_mutex was missed when converting to use the enums.

Cc Thomas Gleixner <[email protected]>

Signed-off-by Brad Mouring <[email protected]>

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

---
 kernel/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

kernel/rtmutex.c +1 -1

index 3f169f882775..8c29e48afa3a 100644
@@ -1166,7 +1166,7 @@ static void  noinline __sched rt_spin_lock_slowlock(struct rt_mutex *lock)
 	__set_current_state(TASK_UNINTERRUPTIBLE);
 	pi_unlock(&self->pi_lock);
 
-	ret = task_blocks_on_rt_mutex(lock, &waiter, self, 0);
+	ret = task_blocks_on_rt_mutex(lock, &waiter, self, RT_MUTEX_MIN_CHAINWALK);
 	BUG_ON(ret);
 
 	for (;;) {

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #4 lore raw

PATCH 4/10 dump stack: dont disable preemption during trace

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <[email protected]>

I see here large latencies during a stack dump on x86. The preempt_disable() and get_cpu() should forbid moving the task to another CPU during a stack dump and avoiding two stack traces in parallel on the same CPU. However a stack trace from a second CPU may still happen in parallel. Also nesting is allowed so a stack trace happens in process-context and we may have another one from IRQ context. With migrate disable we keep this code preemptible and allow a second backtrace on the same CPU by another task.

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

---
 arch/x86/kernel/dumpstack_64.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

arch/x86/kernel/dumpstack_64.c +4 -4

index 66e274a3d968..37aee503a7ba 100644
@@ -114,7 +114,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
 		unsigned long *stack, unsigned long bp,
 		const struct stacktrace_ops *ops, void *data)
 {
-	const unsigned cpu = get_cpu();
+	const unsigned cpu = get_cpu_light();
 	unsigned long *irq_stack_end =
 		(unsigned long *)per_cpu(irq_stack_ptr, cpu);
 	unsigned used = 0;

@@ -191,7 +191,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
 	 * This handles the process stack:
 	 */
 	bp = ops->walk_stack(tinfo, stack, bp, ops, data, NULL, &graph);
-	put_cpu();
+	put_cpu_light();
 }
 EXPORT_SYMBOL(dump_trace);

@@ -205,7 +205,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 	int cpu;
 	int i;
 
-	preempt_disable();
+	migrate_disable();
 	cpu = smp_processor_id();
 
 	irq_stack_end	= (unsigned long *)(per_cpu(irq_stack_ptr, cpu));

@@ -238,7 +238,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 		pr_cont(" %016lx", *stack++);
 		touch_nmi_watchdog();
 	}
-	preempt_enable();
+	migrate_enable();
 
 	pr_cont("\n");
 	show_trace_log_lvl(task, regs, sp, bp, log_lvl);

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #5 lore raw

PATCH 5/10 net: Make synchronize_rcu_expedited() conditional on !RT_FULL

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Josh Cartwright <[email protected]>

While the use of synchronize_rcu_expedited() might make synchronize_net() "faster", it does so at significant cost on RT systems, as expediting a grace period forcibly preempts any high-priority RT tasks (via the stop_machine() mechanism).

Without this change, we can observe a latency spike up to 30us with cyclictest by rapidly unplugging/reestablishing an ethernet link.

Signed-off-by Josh Cartwright <[email protected]>

Acked-by Eric Dumazet <[email protected]>

Acked-by David S. Miller <[email protected]>

Cc Paul E. McKenney <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

net/core/dev.c +1 -1

index a478f77e4322..3a531a6fec33 100644
@@ -5838,7 +5838,7 @@ EXPORT_SYMBOL(free_netdev);
 void synchronize_net(void)
 {
 	might_sleep();
-	if (rtnl_is_locked())
+	if (rtnl_is_locked() && !IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
 		synchronize_rcu_expedited();
 	else
 		synchronize_rcu();

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 22:20 UTC #6 lore raw

PATCH 6/10 net/core/cpuhotplug: Drain input_pkt_queue lockless

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Grygorii Strashko <[email protected]>

I can constantly see below error report with 4.1 RT-kernel on TI ARM dra7-evm if I'm trying to unplug cpu1:

[   57.737589] CPU1: shutdown
[   57.767537] BUG: spinlock bad magic on CPU#0, sh/137
[   57.767546]  lock: 0xee994730, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
[   57.767552] CPU: 0 PID: 137 Comm: sh Not tainted 4.1.10-rt8-01700-g2c38702-dirty #55
[   57.767555] Hardware name: Generic DRA74X (Flattened Device Tree)
[   57.767568] [<c001acd0>] (unwind_backtrace) from [<c001534c>] (show_stack+0x20/0x24)
[   57.767579] [<c001534c>] (show_stack) from [<c075560c>] (dump_stack+0x84/0xa0)
[   57.767593] [<c075560c>] (dump_stack) from [<c00aca48>] (spin_dump+0x84/0xac)
[   57.767603] [<c00aca48>] (spin_dump) from [<c00acaa4>] (spin_bug+0x34/0x38)
[   57.767614] [<c00acaa4>] (spin_bug) from [<c00acc10>] (do_raw_spin_lock+0x168/0x1c0)
[   57.767624] [<c00acc10>] (do_raw_spin_lock) from [<c075b4cc>] (_raw_spin_lock+0x4c/0x54)
[   57.767631] [<c075b4cc>] (_raw_spin_lock) from [<c07599fc>] (rt_spin_lock_slowlock+0x5c/0x374)
[   57.767638] [<c07599fc>] (rt_spin_lock_slowlock) from [<c075bcf4>] (rt_spin_lock+0x38/0x70)
[   57.767649] [<c075bcf4>] (rt_spin_lock) from [<c06333c0>] (skb_dequeue+0x28/0x7c)
[   57.767662] [<c06333c0>] (skb_dequeue) from [<c06476ec>] (dev_cpu_callback+0x1b8/0x240)
[   57.767673] [<c06476ec>] (dev_cpu_callback) from [<c007566c>] (notifier_call_chain+0x3c/0xb4)

The reason is that skb_dequeue is taking skb->lock, but RT changed the core code to use a raw spinlock. The non-raw lock is not initialized on purpose to catch exactly this kind of problem.

Fixes 91df05da13a6 'net: Use skbufhead with raw lock'

---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

net/core/dev.c +1 -1

index 3a531a6fec33..864f7ae42c08 100644
@@ -6088,7 +6088,7 @@ static int dev_cpu_callback(struct notifier_block *nfb,
 		netif_rx(skb);
 		input_queue_head_incr(oldsd);
 	}
-	while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) {
+	while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {
 		netif_rx(skb);
 		input_queue_head_incr(oldsd);
 	}

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #7 lore raw

PATCH 7/10 irqwork: Move irq safe work to irq context

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <[email protected]>

On architectures where arch_irq_work_has_interrupt() returns false, we end up running the irq safe work from the softirq context. That results in a potential deadlock in the scheduler irq work which expects that function to be called with interrupts disabled.

Split the irq_work_tick() function into a hard and soft variant. Call the hard variant from the tick interrupt and add the soft variant to the timer softirq.

Reported-and-tested-by Yanjiang Jin <[email protected]>

---
 include/linux/irq_work.h | 6 ++++++
 kernel/irq_work.c        | 9 +++++++++
 kernel/timer.c           | 6 ++----
 3 files changed, 17 insertions(+), 4 deletions(-)

include/linux/irq_work.h +6 -0

index 4a8c7a2df480..ccd736ebee9e 100644
@@ -44,4 +44,10 @@ bool irq_work_needs_cpu(void);
 static inline bool irq_work_needs_cpu(void) { return false; }
 #endif
 
+#if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL)
+void irq_work_tick_soft(void);
+#else
+static inline void irq_work_tick_soft(void) { }
+#endif
+
 #endif /* _LINUX_IRQ_WORK_H */

kernel/irq_work.c +9 -0

index af8ceafc94e4..883bb73698b9 100644
@@ -163,8 +163,17 @@ void irq_work_tick(void)
 
 	if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
 		irq_work_run_list(raised);
+
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+		irq_work_run_list(this_cpu_ptr(&lazy_list));
+}
+
+#if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL)
+void irq_work_tick_soft(void)
+{
 	irq_work_run_list(this_cpu_ptr(&lazy_list));
 }
+#endif
 
 /*
  * Synchronize against the irq_work @entry, ensures the entry is not

kernel/timer.c +2 -4

index ff272e20ee0c..2fd6ea5c6519 100644
@@ -1450,7 +1450,7 @@ void update_process_times(int user_tick)
 	scheduler_tick();
 	run_local_timers();
 	rcu_check_callbacks(cpu, user_tick);
-#if defined(CONFIG_IRQ_WORK) && !defined(CONFIG_PREEMPT_RT_FULL)
+#if defined(CONFIG_IRQ_WORK)
 	if (in_irq())
 		irq_work_run();
 #endif

@@ -1466,9 +1466,7 @@ static void run_timer_softirq(struct softirq_action *h)
 
 	hrtimer_run_pending();
 
-#if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL)
-	irq_work_tick();
-#endif
+	irq_work_tick_soft();
 
 	if (time_after_eq(jiffies, base->timer_jiffies))
 		__run_timers(base);

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #8 lore raw

PATCH 8/10 sched: Introduce the trace_sched_waking tracepoint

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <[email protected]>

Upstream commit fbd705a0c6184580d0e2fbcbd47a37b6e5822511

Mathieu reported that since 317f394160e9 ("sched: Move the second half of ttwu() to the remote cpu") trace_sched_wakeup() can happen out of context of the waker.

This is a problem when you want to analyse wakeup paths because it is now very hard to correlate the wakeup event to whoever issued the wakeup.

OTOH trace_sched_wakeup() is issued at the point where we set p->state = TASK_RUNNING, which is right were we hand the task off to the scheduler, so this is an important point when looking at scheduling behaviour, up to here its been the wakeup path everything hereafter is due to scheduler policy.

To bridge this gap, introduce a second tracepoint: trace_sched_waking. It is guaranteed to be called in the waker context.

[ Ported to linux-4.1.y-rt kernel by Mathieu Desnoyers. Resolved
conflict: try_to_wake_up_local() does not exist in -rt kernel. Removed its instrumentation hunk. ]

Reported-by Mathieu Desnoyers <[email protected]>

CC Julien Desfossez <[email protected]>

CC Peter Zijlstra (Intel) <[email protected]>

Cc Francis Giraldeau <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Mike Galbraith <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Steven Rostedt <[email protected]>

Cc Thomas Gleixner <[email protected]>

CC Ingo Molnar <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Mathieu Desnoyers <[email protected]>

---
 include/trace/events/sched.h      | 30 +++++++++++++++++++++---------
 kernel/sched/core.c               |  8 +++++---
 kernel/trace/trace_sched_switch.c |  2 +-
 kernel/trace/trace_sched_wakeup.c |  2 +-
 4 files changed, 28 insertions(+), 14 deletions(-)

include/trace/events/sched.h +21 -9

index e5586caff67a..1ff7042e572d 100644
@@ -55,9 +55,9 @@ TRACE_EVENT(sched_kthread_stop_ret,
  */
 DECLARE_EVENT_CLASS(sched_wakeup_template,
 
-	TP_PROTO(struct task_struct *p, int success),
+	TP_PROTO(struct task_struct *p),
 
-	TP_ARGS(p, success),
+	TP_ARGS(p),
 
 	TP_STRUCT__entry(
 		__array(	char,	comm,	TASK_COMM_LEN	)

@@ -71,28 +71,40 @@ DECLARE_EVENT_CLASS(sched_wakeup_template,
 		memcpy(__entry->comm, p->comm, TASK_COMM_LEN);
 		__entry->pid		= p->pid;
 		__entry->prio		= p->prio;
-		__entry->success	= success;
+		__entry->success	= 1; /* rudiment, kill when possible */
 		__entry->target_cpu	= task_cpu(p);
 	)
 	TP_perf_assign(
 		__perf_task(p);
 	),
 
-	TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d",
+	TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d",
 		  __entry->comm, __entry->pid, __entry->prio,
-		  __entry->success, __entry->target_cpu)
+		  __entry->target_cpu)
 );
 
+/*
+ * Tracepoint called when waking a task; this tracepoint is guaranteed to be
+ * called from the waking context.
+ */
+DEFINE_EVENT(sched_wakeup_template, sched_waking,
+	     TP_PROTO(struct task_struct *p),
+	     TP_ARGS(p));
+
+/*
+ * Tracepoint called when the task is actually woken; p->state == TASK_RUNNNG.
+ * It it not always called from the waking context.
+ */
 DEFINE_EVENT(sched_wakeup_template, sched_wakeup,
-	     TP_PROTO(struct task_struct *p, int success),
-	     TP_ARGS(p, success));
+	     TP_PROTO(struct task_struct *p),
+	     TP_ARGS(p));
 
 /*
  * Tracepoint for waking up a new task:
  */
 DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new,
-	     TP_PROTO(struct task_struct *p, int success),
-	     TP_ARGS(p, success));
+	     TP_PROTO(struct task_struct *p),
+	     TP_ARGS(p));
 
 #ifdef CREATE_TRACE_POINTS
 static inline long __trace_sched_switch_state(struct task_struct *p)

kernel/sched/core.c +5 -3

index 23e289ae4270..6c21a28689b9 100644
@@ -1394,9 +1394,9 @@ static void
 ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
 {
 	check_preempt_curr(rq, p, wake_flags);
-	trace_sched_wakeup(p, true);
-
 	p->state = TASK_RUNNING;
+	trace_sched_wakeup(p);
+
 #ifdef CONFIG_SMP
 	if (p->sched_class->task_woken)
 		p->sched_class->task_woken(rq, p);

@@ -1579,6 +1579,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	if (!(wake_flags & WF_LOCK_SLEEPER))
 		p->saved_state = TASK_RUNNING;
 
+	trace_sched_waking(p);
+
 	success = 1; /* we're going to change ->state */
 	cpu = task_cpu(p);

@@ -1830,7 +1832,7 @@ void wake_up_new_task(struct task_struct *p)
 	rq = __task_rq_lock(p);
 	activate_task(rq, p, 0);
 	p->on_rq = 1;
-	trace_sched_wakeup_new(p, true);
+	trace_sched_wakeup_new(p);
 	check_preempt_curr(rq, p, WF_FORK);
 #ifdef CONFIG_SMP
 	if (p->sched_class->task_woken)

kernel/trace/trace_sched_switch.c +1 -1

index 4e98e3b257a3..82fe794af532 100644
@@ -106,7 +106,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
 }
 
 static void
-probe_sched_wakeup(void *ignore, struct task_struct *wakee, int success)
+probe_sched_wakeup(void *ignore, struct task_struct *wakee)
 {
 	struct trace_array_cpu *data;
 	unsigned long flags;

kernel/trace/trace_sched_wakeup.c +1 -1

index fee77e15d815..8e967ca56006 100644
@@ -458,7 +458,7 @@ static void wakeup_reset(struct trace_array *tr)
 }
 
 static void
-probe_wakeup(void *ignore, struct task_struct *p, int success)
+probe_wakeup(void *ignore, struct task_struct *p)
 {
 	struct trace_array_cpu *data;
 	int cpu = smp_processor_id();

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #9 lore raw

PATCH 9/10 rtmutex: Have slowfn of rt_mutex_timed_fastlock() use enum

3.10.97-rt106-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (Red Hat)" <[email protected]>

The backport of commit 8930ed80f970 "rtmutex: Cleanup deadlock detector debug logic" had conflicts, and the conflict resolution changed rt_mutex_timed_fastlock()'s parameter to an enum, but missed changing its slowfn's prototype.

---
 kernel/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

kernel/rtmutex.c +1 -1

index 8c29e48afa3a..a809539f443c 100644
@@ -1636,7 +1636,7 @@ rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
 			enum rtmutex_chainwalk chwalk,
 			int (*slowfn)(struct rt_mutex *lock, int state,
 				      struct hrtimer_sleeper *timeout,
-				      int detect_deadlock))
+				      enum rtmutex_chainwalk chwalk))
 {
 	if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
 	    likely(rt_mutex_cmpxchg(lock, NULL, current))) {

Signature · 1 line

2.7.0

Steven Rostedt

author maintainer

2016-02-26 21:41 UTC #10 lore raw

PATCH 10/10 Linux 3.10.97-rt106-rc1