linux-kernel - Re: race leading to held mutexes, inode

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Date:	Tue, 1 Apr 2008 21:28:20 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Sapan Bhatia" <sapan.bhatia@...il.com>
Cc:	linux-kernel@...r.kernel.org, daniel@...ac.com
Subject: Re: race leading to held mutexes, inode_cache corruption

On Wed, 2 Apr 2008 00:13:04 -0400 "Sapan Bhatia" <sapan.bhatia@...il.com> wrote:

> >
> >
> > That's the only way in which I can interpret your second paragraph, but as
> > far as I can tell the code cannot do that.
> >
> > Can you provide more detail?
> >
> 
> On running the example again, it seems that attributing the problem to a
> generic locking bug was a misdiagnosis. I apologize for the misinformation.
> The error is more likely a path with a dangling mutex_lock somewhere, or
> something else. I'll investigate further and try to provide a more detailed
> description of the problem when I have something concrete.
> 

OK, thanks.

Recent kernels have this:

config DEBUG_LOCK_ALLOC
	bool "Lock debugging: detect incorrect freeing of live locks"
	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
	select DEBUG_SPINLOCK
	select DEBUG_MUTEXES
	select LOCKDEP
	help
	 This feature will check whether any held lock (spinlock, rwlock,
	 mutex or rwsem) is incorrectly freed by the kernel, via any of the
	 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
	 vfree(), etc.), whether a live lock is incorrectly reinitialized via
	 spin_lock_init()/mutex_init()/etc., or whether there is any lock
	 held during task exit.

which seems rather relevant, no? ;)
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