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SubjectRe: .29rc2 lockdep report. fb_mmap vs sys_mmap2
On 2009-01-18 03:00, Johannes Weiner wrote:
> On Sat, Jan 17, 2009 at 06:19:25PM -0500, Dave Jones wrote:
>> Two mmaps enter! Fight!
>>
>>
>> =======================================================
>> [ INFO: possible circular locking dependency detected ]
>> 2.6.29-0.41.rc2.fc11.i686 #1
>> -------------------------------------------------------
>> plymouthd/669 is trying to acquire lock:
>> (&fb_info->lock){--..}, at: [<c055355c>] fb_mmap+0x87/0x156
>>
>> but task is already holding lock:
>> (&mm->mmap_sem){----}, at: [<c0406a5d>] sys_mmap2+0x44/0x7b
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #1 (&mm->mmap_sem){----}:
>> [<c044fef3>] __lock_acquire+0x9af/0xb22
>> [<c04500c1>] lock_acquire+0x5b/0x81
>> [<c048e036>] might_fault+0x60/0x80
>> [<c053dedc>] copy_to_user+0x2c/0xfc
>> [<c05542cc>] fb_ioctl+0x247/0x338
>> [<c04b0c9f>] vfs_ioctl+0x22/0x69
>> [<c04b1214>] do_vfs_ioctl+0x46a/0x4a3
>> [<c04b128d>] sys_ioctl+0x40/0x5a
>> [<c0403b76>] syscall_call+0x7/0xb
>> [<ffffffff>] 0xffffffff
>>
>> -> #0 (&fb_info->lock){--..}:
>> [<c044fdc8>] __lock_acquire+0x884/0xb22
>> [<c04500c1>] lock_acquire+0x5b/0x81
>> [<c06e1b98>] __mutex_lock_common+0xd5/0x329
>> [<c06e1e84>] mutex_lock_nested+0x2e/0x36
>> [<c055355c>] fb_mmap+0x87/0x156
>> [<c0494620>] mmap_region+0x22b/0x43c
>> [<c0494aa2>] do_mmap_pgoff+0x271/0x2d1
>> [<c0406a73>] sys_mmap2+0x5a/0x7b
>> [<c0403b76>] syscall_call+0x7/0xb
>> [<ffffffff>] 0xffffffff
>>
>> other info that might help us debug this:
>>
>> 1 lock held by plymouthd/669:
>> #0: (&mm->mmap_sem){----}, at: [<c0406a5d>] sys_mmap2+0x44/0x7b
>>
>> stack backtrace:
>> Pid: 669, comm: plymouthd Not tainted 2.6.29-0.41.rc2.fc11.i686 #1
>> Call Trace:
>> [<c06e09b6>] ? printk+0xf/0x11
>> [<c044f32d>] print_circular_bug_tail+0x5d/0x68
>> [<c044fdc8>] __lock_acquire+0x884/0xb22
>> [<c04500c1>] lock_acquire+0x5b/0x81
>> [<c055355c>] ? fb_mmap+0x87/0x156
>> [<c06e1b98>] __mutex_lock_common+0xd5/0x329
>> [<c055355c>] ? fb_mmap+0x87/0x156
>> [<c06e1e84>] mutex_lock_nested+0x2e/0x36
>> [<c055355c>] ? fb_mmap+0x87/0x156
>> [<c055355c>] fb_mmap+0x87/0x156
>> [<c0494620>] mmap_region+0x22b/0x43c
>> [<c0494aa2>] do_mmap_pgoff+0x271/0x2d1
>> [<c0406a73>] sys_mmap2+0x5a/0x7b
>> [<c0403b76>] syscall_call+0x7/0xb
>
> I reported this one already some time ago [1], Andrea Righi [cc'd]
> also had a fix [2] but it seemed to not have made it in. Andrea,
> perhaps you can resend it?
>
> Hannes
>
> [1] http://lkml.org/lkml/2008/10/22/759
> [2] http://lkml.org/lkml/2008/10/28/377

Sure, I can resend it soon, after a test.

-Andrea


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