Messages in this thread | | | Date | Tue, 23 Aug 2011 07:59:20 -0400 | Subject | Re: 3.1.0-rc3 -- INFO: possible circular locking dependency detected | From | Josh Boyer <> |
| |
On Tue, Aug 23, 2011 at 7:49 AM, Dave Chinner <david@fromorbit.com> wrote: > On Tue, Aug 23, 2011 at 07:35:00AM -0400, Josh Boyer wrote: >> On Tue, Aug 23, 2011 at 12:39 AM, Miles Lane <miles.lane@gmail.com> wrote: >> > [ INFO: possible circular locking dependency detected ] >> > 3.1.0-rc3 #2 >> > ------------------------------------------------------- >> > dconf-service/1836 is trying to acquire lock: >> > (&sb->s_type->i_mutex_key#12){+.+.+.}, at: [<ffffffff8116df1a>] >> > ext4_evict_inode+0x88/0x32b >> > >> > but task is already holding lock: >> > (&mm->mmap_sem){++++++}, at: [<ffffffff810d4393>] sys_munmap+0x36/0x5b >> > >> > which lock already depends on the new lock. >> > >> > the existing dependency chain (in reverse order) is: >> > >> > -> #1 (&mm->mmap_sem){++++++}: >> > [<ffffffff8106933a>] lock_acquire+0x129/0x14e >> > [<ffffffff810cddbd>] might_fault+0x68/0x8b >> > [<ffffffff810fcf5e>] filldir+0x6a/0xc2 >> > [<ffffffff811651a1>] call_filldir+0x91/0xb8 >> > [<ffffffff811654bf>] ext4_readdir+0x1af/0x510 >> > [<ffffffff810fd1a4>] vfs_readdir+0x76/0xac >> > [<ffffffff810fd2b6>] sys_getdents+0x79/0xc9 >> > [<ffffffff814162fb>] system_call_fastpath+0x16/0x1b >> > >> > -> #0 (&sb->s_type->i_mutex_key#12){+.+.+.}: >> > [<ffffffff81068b10>] __lock_acquire+0xa5e/0xd52 >> > [<ffffffff8106933a>] lock_acquire+0x129/0x14e >> > [<ffffffff8140f1a2>] __mutex_lock_common+0x64/0x413 >> > [<ffffffff8140f5b0>] mutex_lock_nested+0x16/0x18 >> > [<ffffffff8116df1a>] ext4_evict_inode+0x88/0x32b >> > [<ffffffff81102d8a>] evict+0x94/0x14e >> > [<ffffffff81102fd0>] iput+0x18c/0x195 >> > [<ffffffff810ffdd4>] dentry_kill+0x11e/0x140 >> > [<ffffffff8110019b>] dput+0xd4/0xe4 >> > [<ffffffff810efac3>] fput+0x1a5/0x1bd >> > [<ffffffff810d3214>] remove_vma+0x37/0x5f >> > [<ffffffff810d4239>] do_munmap+0x2ed/0x306 >> > [<ffffffff810d43a1>] sys_munmap+0x44/0x5b >> > [<ffffffff814162fb>] system_call_fastpath+0x16/0x1b >> > >> > other info that might help us debug this: >> > >> > Possible unsafe locking scenario: >> > >> > CPU0 CPU1 >> > ---- ---- >> > lock(&mm->mmap_sem); >> > lock(&sb->s_type->i_mutex_key); >> > lock(&mm->mmap_sem); >> > lock(&sb->s_type->i_mutex_key); >> > >> > *** DEADLOCK *** >> >> This one was reported yesterday: https://lkml.org/lkml/2011/8/21/163 >> and we're hoping Ted (or someone else from the ext4 camp) can comment >> on why ext4_evict_inode is holding i_mutex. > > Actually, the problem has nothing to do with ext4. the problem is > that remove_vma() is holding the mmap_sem while calling fput(). The > correct locking order is i_mutex->mmap_sem, as documented in > mm/filemap.c: > > * ->i_mutex (generic_file_buffered_write) > * ->mmap_sem (fault_in_pages_readable->do_page_fault) > > > The way remove_vma() calls fput() also triggers lockdep reports in > XFS and it will do so with any filesystem that takes an inode > specific lock in it's evict() processing. IOWs, remove_vma() needs > fixing, not ext4....
Er... ok. So the remove_vma code hasn't changed since 2008. We're only seeing this issue now because the debugging code has improved, or?
At any rate, the proposed solution is to make remove_vma drop mmap_sem before calling fput, or make it not call fput, or?
josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |