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Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:2731 check_flags (ftrace)

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From: Steven Rostedt <rostedt@...>
To: Vegard Nossum <vegard.nossum@...>
Cc: Linux Kernel Mailing List <linux-kernel@...>, Ingo Molnar <mingo@...>, Thomas Gleixner <tglx@...>, Peter Zijlstra <peterz@...>
Subject: Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:2731 check_flags (ftrace)
Date: Wednesday, July 16, 2008 - 12:13 am

On Wed, 16 Jul 2008, Vegard Nossum wrote:


Maybe.

Things get weird between lockdep and ftrace because ftrace can be called
within lockdep internal code (via the mcount pointer) and lockdep can be
called with ftrace (via spin_locks).

Can you try this patch out and see if it fixes your problem. I only
compiled tested it.

Note: I'll be traveling for the next couple of weeks, so I will be on and
off with email.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 kernel/trace/trace_sched_wakeup.c |   27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

Index: linux-compile.git/kernel/trace/trace_sched_wakeup.c
===================================================================
--- linux-compile.git.orig/kernel/trace/trace_sched_wakeup.c	2008-07-15 23:56:50.000000000 -0400
+++ linux-compile.git/kernel/trace/trace_sched_wakeup.c	2008-07-16 00:10:05.000000000 -0400
@@ -26,7 +26,8 @@ static struct task_struct	*wakeup_task;
 static int			wakeup_cpu;
 static unsigned			wakeup_prio = -1;

-static DEFINE_SPINLOCK(wakeup_lock);
+static raw_spinlock_t wakeup_lock =
+	(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;

 static void __wakeup_reset(struct trace_array *tr);

@@ -56,7 +57,8 @@ wakeup_tracer_call(unsigned long ip, uns
 	if (unlikely(disabled != 1))
 		goto out;

-	spin_lock_irqsave(&wakeup_lock, flags);
+	local_irq_save(flags);
+	__raw_spin_lock(&wakeup_lock);

 	if (unlikely(!wakeup_task))
 		goto unlock;
@@ -71,7 +73,8 @@ wakeup_tracer_call(unsigned long ip, uns
 	trace_function(tr, data, ip, parent_ip, flags);

  unlock:
-	spin_unlock_irqrestore(&wakeup_lock, flags);
+	__raw_spin_unlock(&wakeup_lock);
+	local_irq_restore(flags);

  out:
 	atomic_dec(&data->disabled);
@@ -145,7 +148,8 @@ wakeup_sched_switch(void *private, void
 	if (likely(disabled != 1))
 		goto out;

-	spin_lock_irqsave(&wakeup_lock, flags);
+	local_irq_save(flags);
+	__raw_spin_lock(&wakeup_lock);

 	/* We could race with grabbing wakeup_lock */
 	if (unlikely(!tracer_enabled || next != wakeup_task))
@@ -174,7 +178,8 @@ wakeup_sched_switch(void *private, void

 out_unlock:
 	__wakeup_reset(tr);
-	spin_unlock_irqrestore(&wakeup_lock, flags);
+	__raw_spin_unlock(&wakeup_lock);
+	local_irq_restore(flags);
 out:
 	atomic_dec(&tr->data[cpu]->disabled);
 }
@@ -209,8 +214,6 @@ static void __wakeup_reset(struct trace_
 	struct trace_array_cpu *data;
 	int cpu;

-	assert_spin_locked(&wakeup_lock);
-
 	for_each_possible_cpu(cpu) {
 		data = tr->data[cpu];
 		tracing_reset(data);
@@ -229,9 +232,11 @@ static void wakeup_reset(struct trace_ar
 {
 	unsigned long flags;

-	spin_lock_irqsave(&wakeup_lock, flags);
+	local_irq_save(flags);
+	__raw_spin_lock(&wakeup_lock);
 	__wakeup_reset(tr);
-	spin_unlock_irqrestore(&wakeup_lock, flags);
+	__raw_spin_unlock(&wakeup_lock);
+	local_irq_restore(flags);
 }

 static void
@@ -252,7 +257,7 @@ wakeup_check_start(struct trace_array *t
 		goto out;

 	/* interrupts should be off from try_to_wake_up */
-	spin_lock(&wakeup_lock);
+	__raw_spin_lock(&wakeup_lock);

 	/* check for races. */
 	if (!tracer_enabled || p->prio >= wakeup_prio)
@@ -274,7 +279,7 @@ wakeup_check_start(struct trace_array *t
 		       CALLER_ADDR1, CALLER_ADDR2, flags);

 out_locked:
-	spin_unlock(&wakeup_lock);
+	__raw_spin_unlock(&wakeup_lock);
 out:
 	atomic_dec(&tr->data[cpu]->disabled);
 }
--
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Messages in current thread:
4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:2731 c..., Vegard Nossum, (Tue Jul 15, 9:55 pm)
Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:27..., Steven Rostedt, (Wed Jul 16, 12:13 am)
Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:27..., Vegard Nossum, (Wed Jul 16, 5:32 am)
Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:27..., Ingo Molnar, (Fri Jul 18, 7:47 am)
Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:27..., Steven Rostedt, (Wed Jul 16, 7:36 am)
Re: 4d3702b6 (post-v2.6.26): WARNING: at kernel/lockdep.c:27..., Steven Rostedt, (Tue Jul 15, 10:05 pm)