lkml.org 
[lkml]   [2012]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Linus GIT (3.3.0-rc6+) -- INFO: possible circular locking dependency detected
On Mon, Mar 05, 2012 at 04:08:55PM -0500, Miles Lane wrote:

> [ 107.839634] -> #1 (&mm->mmap_sem){++++++}:
[readdir() grabs ->mmap_sem under ->i_mutex - true, but irrelevant; more
to the point, write() on just about anything will grab ->mmap_sem under
->i_mutex, and that one happens for non-directories]

> [ 107.839665] -> #0 (&sb->s_type->i_mutex_key#13){+.+.+.}:
[generic_file_aio_write() grabs ->i_mutex after being called from
vfs_write(), called from...]
> [ 107.839691] [<ffffffff810e6333>] vfs_write+0xa7/0xee
> [ 107.839694] [<ffffffffa037f266>]
> ecryptfs_write_lower+0x4e/0x73 [ecryptfs]
> [ 107.839700] [<ffffffffa03803d3>]
> ecryptfs_encrypt_page+0x11c/0x182 [ecryptfs]
> [ 107.839704] [<ffffffffa037e967>]
> ecryptfs_writepage+0x31/0x73 [ecryptfs]
> [ 107.839708] [<ffffffff810b448b>] __writepage+0x12/0x31
> [ 107.839710] [<ffffffff810b4b25>] write_cache_pages+0x1e6/0x310
> [ 107.839713] [<ffffffff810b4c8d>] generic_writepages+0x3e/0x54
> [ 107.839716] [<ffffffff810b5e05>] do_writepages+0x26/0x28
> [ 107.839719] [<ffffffff810ae1e4>] __filemap_fdatawrite_range+0x4e/0x50
> [ 107.839722] [<ffffffff810aed55>] filemap_fdatawrite+0x1a/0x1c
> [ 107.839725] [<ffffffff810aed72>] filemap_write_and_wait+0x1b/0x36
> [ 107.839727] [<ffffffffa037c1bb>]
> ecryptfs_vma_close+0x17/0x19 [ecryptfs]

Bloody wonderful... That would do it, all right. Forget about readdir(),
the deadlock is real and has nothing to do with directories. Ecryptfs bug,
AFAICS.

Thread A:
mmap something on ecryptfs, dirty it.
Thread B: open underlying file for write,
later
Thread A: munmap() | Thread B: write() (from unrelated buffer)

A holds ->mmap_sem, B holds ->i_mutex.
A is blocked essentially on attempt to do what B is doing (write to underlying
file; any mutex whatever_fs_write() might be holding around copy_from_user()
will do for that deadlock).
B is blocked trying to fault some pages in.

Fun...


\
 
 \ /
  Last update: 2012-03-05 22:35    [W:0.048 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site