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Date: Mon, 20 Jul 2009 04:12:12 -0400
From: Frederic Weisbecker <fweisbec@...il.com>
To: Li Zefan <lizf@...fujitsu.com>
Cc: hpa@...or.com, linux-kernel@...r.kernel.org,
a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu,
linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched: Pull up the might_sleep() check into
cond_resched()
On Mon, Jul 20, 2009 at 02:50:19PM +0800, Li Zefan wrote:
> > Commit-ID: 613afbf83298efaead05ebcac23d2285609d7160
> > Gitweb: http://git.kernel.org/tip/613afbf83298efaead05ebcac23d2285609d7160
> > Author: Frederic Weisbecker <fweisbec@...il.com>
> > AuthorDate: Thu, 16 Jul 2009 15:44:29 +0200
> > Committer: Ingo Molnar <mingo@...e.hu>
> > CommitDate: Sat, 18 Jul 2009 15:51:44 +0200
> >
> > sched: Pull up the might_sleep() check into cond_resched()
> >
> > might_sleep() is called late-ish in cond_resched(), after the
> > need_resched()/preempt enabled/system running tests are
> > checked.
> >
> > It's better to check the sleeps while atomic earlier and not
> > depend on some environment datas that reduce the chances to
> > detect a problem.
> >
> > Also define cond_resched_*() helpers as macros, so that the
> > FILE/LINE reported in the sleeping while atomic warning
> > displays the real origin and not sched.h
> >
>
> I guess it's this patch that causes lots of "BUG"
>
> BUG: sleeping function called from invalid context at fs/jbd/commit.c:902
> in_atomic(): 0, irqs_disabled(): 0, pid: 64, name: kjournald
> INFO: lockdep is turned off.
> Pid: 64, comm: kjournald Tainted: GF 2.6.31-rc3-tip #15
> Call Trace:
> [<c042cbd1>] __might_sleep+0xda/0xdf
> [<c053e9f4>] journal_commit_transaction+0xb03/0xc5f
> [<c043ecc4>] ? try_to_del_timer_sync+0x48/0x4f
> [<c0541394>] kjournald+0xcf/0x1fe
> [<c0448998>] ? autoremove_wake_function+0x0/0x34
> [<c05412c5>] ? kjournald+0x0/0x1fe
> [<c0448708>] kthread+0x6b/0x70
> [<c044869d>] ? kthread+0x0/0x70
> [<c040364b>] kernel_thread_helper+0x7/0x10
> BUG: sleeping function called from invalid context at fs/dcache.c:512
> in_atomic(): 0, irqs_disabled(): 0, pid: 2005, name: bash
> INFO: lockdep is turned off.
> Pid: 2005, comm: bash Tainted: GF 2.6.31-rc3-tip #15
> Call Trace:
> [<c042cbd1>] __might_sleep+0xda/0xdf
> [<c04cae29>] __shrink_dcache_sb+0x208/0x27a
> [<c04cb038>] shrink_dcache_parent+0x2c/0xcf
> [<c04f8371>] proc_flush_task+0xa7/0x194
> [<c0437553>] release_task+0x29/0x3b4
> [<c0437fe0>] wait_consider_task+0x702/0xa91
> [<c043844d>] do_wait+0xde/0x276
> [<c0430f6e>] ? default_wake_function+0x0/0x12
> [<c0438672>] sys_wait4+0x8d/0xa6
> [<c04a3c65>] ? might_fault+0x85/0x87
> [<c04386a3>] sys_waitpid+0x18/0x1a
> [<c0402ab8>] sysenter_do_call+0x12/0x36
Hm, I can read that in fs/dcache.c:512
/* dentry->d_lock was dropped in prune_one_dentry() */
cond_resched_lock(&dcache_lock);
Isn't it a mususe of cond_resched_lock() ?
In this case, dcache.c should be fixed.
Anyway a generic fix could be the following.
Can you tell me if this works for you?
Thanks!
---
From: Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH] sched: Check if the spinlock is locked in cond_resched_lock()
Some uses of cond_resched_lock() might involve an
unlocked spinlock, resulting in spurious sleep in
atomic warnings.
Check whether the spinlock is actually locked and
take that into account in the might_sleep() check.
Reported-by: Li Zefan <lizf@...fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
diff --git a/include/linux/sched.h b/include/linux/sched.h
index cb070dc..2789658 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2294,9 +2294,10 @@ extern int _cond_resched(void);
extern int __cond_resched_lock(spinlock_t *lock);
-#define cond_resched_lock(lock) ({ \
- __might_sleep(__FILE__, __LINE__, PREEMPT_OFFSET); \
- __cond_resched_lock(lock); \
+#define cond_resched_lock(lock) ({ \
+ __might_sleep(__FILE__, __LINE__, spin_is_locked(lock) ? \
+ PREEMPT_OFFSET : 0); \
+ __cond_resched_lock(lock); \
})
extern int __cond_resched_softirq(void);
--
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