Re: Reiser4: possible circular locking dependency detected

[Edward Shishkin <edward.shishkin@gmail.com>]

Laurent Riffard wrote:
> Hello,
>
>   

Hi Laurent

> I've got this warning in my logs with 2.6.29-rc5 + reiser4 patches:
>
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.29-rc5-00012-g94aca52 #132
> -------------------------------------------------------
> git/5217 is trying to acquire lock:
>  (&data->latch){----}, at: [<f8bd442b>] get_exclusive_access+0x12/0x1c [reiser4]
>
> but task is already holding lock:
>  (&mm->mmap_sem){----}, at: [<c02067b1>] sys_mmap2+0x44/0x7b
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&mm->mmap_sem){----}:
>        [<c0243477>] __lock_acquire+0x98d/0xb00
>        [<c0243645>] lock_acquire+0x5b/0x81
>        [<c0269d02>] might_fault+0x68/0x88
>   

This is a false positive provided by might_fault(),
introduced in the latest kernels.

User page has to be brought in so that major page
fault does not occur here when the non-exclusive
access is acquired (by read_unix_file).

We need to teach the code somehow to not produce
this false alarm. I'll take a look..

Thanks,
Edward.

>        [<f8be0b92>] reiser4_read_tail+0x60/0xc2 [reiser4]
>        [<f8bd3e9f>] read_unix_file+0x2da/0x3a0 [reiser4]
>        [<f8bd5348>] reiser4_read_careful+0xac/0xf4 [reiser4]
>        [<c027cd28>] vfs_read+0x79/0xaa
>        [<c027cdf2>] sys_read+0x3b/0x60
>        [<c0202fff>] sysenter_do_call+0x12/0x43
>        [<ffffffff>] 0xffffffff
>
> -> #0 (&data->latch){----}:
>        [<c024334c>] __lock_acquire+0x862/0xb00
>        [<c0243645>] lock_acquire+0x5b/0x81
>        [<c03c8d5a>] down_write+0x2a/0x46
>        [<f8bd442b>] get_exclusive_access+0x12/0x1c [reiser4]
>        [<f8bd19ff>] get_exclusive_access_careful+0x10/0x32 [reiser4]
>        [<f8bd30d2>] mmap_unix_file+0x48/0x10a [reiser4]
>        [<f8bd516d>] reiser4_mmap_careful+0xa1/0xe6 [reiser4]
>        [<c026fea9>] mmap_region+0x219/0x3b0
>        [<c0270224>] do_mmap_pgoff+0x1e4/0x230
>        [<c02067c7>] sys_mmap2+0x5a/0x7b
>        [<c0202fff>] sysenter_do_call+0x12/0x43
>        [<ffffffff>] 0xffffffff
>
> other info that might help us debug this:
>
> 1 lock held by git/5217:
>  #0:  (&mm->mmap_sem){----}, at: [<c02067b1>] sys_mmap2+0x44/0x7b
>
> stack backtrace:
> Pid: 5217, comm: git Not tainted 2.6.29-rc5-00012-g94aca52 #132
> Call Trace:
>  [<c03c7800>] ? printk+0xf/0x17
>  [<c02428d3>] print_circular_bug_tail+0x5d/0x68
>  [<c024334c>] __lock_acquire+0x862/0xb00
>  [<c0241280>] ? static_obj+0x6d/0x79
>  [<c0243645>] lock_acquire+0x5b/0x81
>  [<f8bd442b>] ? get_exclusive_access+0x12/0x1c [reiser4]
>  [<c03c8d5a>] down_write+0x2a/0x46
>  [<f8bd442b>] ? get_exclusive_access+0x12/0x1c [reiser4]
>  [<f8bd442b>] get_exclusive_access+0x12/0x1c [reiser4]
>  [<f8bd19ff>] get_exclusive_access_careful+0x10/0x32 [reiser4]
>  [<f8bd30d2>] mmap_unix_file+0x48/0x10a [reiser4]
>  [<f8bd516d>] reiser4_mmap_careful+0xa1/0xe6 [reiser4]
>  [<c026fea9>] mmap_region+0x219/0x3b0
>  [<c0270224>] do_mmap_pgoff+0x1e4/0x230
>  [<c02067c7>] sys_mmap2+0x5a/0x7b
>  [<c0202fff>] sysenter_do_call+0x12/0x43
>
>
> The set of reiser4 patches I'm using is available from http://laurent.riffard.free.fr/reiser4/reiser4-for-2.6.29-rc5/:
> 0001-Reiser4-for-Linux-2.6.28.patch                           
> 0002-reiser4-adjust-to-the-new-aops-fixup.patch               
> 0003-Reiser4-fix-BUG-using-smp_processor_id-in-preemp.patch   
> 0004-Reiser4-Change-current-fs-ug-id-to-current_fs-ug-i.patch 
> 0005-Reiser4-fix-__grab_cache_page-usage.patch                
> 0006-Revert-Reiser4-fix-__grab_cache_page-usage.patch         
> 0007-Reiser4-build-fix.patch                                  
> 0008-reiser4-update-names-of-quota-methods.patch              
>
> ~~
> laurent
>
>
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