Messages in this thread | | | Date | Mon, 23 Jun 2008 08:19:30 +1000 | From | Dave Chinner <> | Subject | Re: [2.6.26-rc7] shrink_icache from pagefault locking (nee: nfsd hangs for a few sec)... |
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[added xfs@oss.sgi.com to cc]
On Sun, Jun 22, 2008 at 10:58:56AM +0100, Daniel J Blueman wrote: > I'm seeing a similar issue [2] to what was recently reported [1] by > Alexander, but with another workload involving XFS and memory > pressure. > > SLUB allocator is in use and config is at http://quora.org/config-client-debug . > > Let me know if you'd like more details/vmlinux objdump etc. > > Thanks, > Daniel > > --- [1] > > http://groups.google.com/group/fa.linux.kernel/browse_thread/thread/e673c9173d45a735/db9213ef39e4e11c > > --- [2] > > ======================================================= > [ INFO: possible circular locking dependency detected ] > 2.6.26-rc7-210c #2 > ------------------------------------------------------- > AutopanoPro/4470 is trying to acquire lock: > (iprune_mutex){--..}, at: [<ffffffff802d94fd>] shrink_icache_memory+0x7d/0x290 > > but task is already holding lock: > (&mm->mmap_sem){----}, at: [<ffffffff805e3e15>] do_page_fault+0x255/0x890 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #2 (&mm->mmap_sem){----}: > [<ffffffff80278f4d>] __lock_acquire+0xbdd/0x1020 > [<ffffffff802793f5>] lock_acquire+0x65/0x90 > [<ffffffff805df5ab>] down_read+0x3b/0x70 > [<ffffffff805e3e3c>] do_page_fault+0x27c/0x890 > [<ffffffff805e16cd>] error_exit+0x0/0xa9 > [<ffffffffffffffff>] 0xffffffffffffffff > > -> #1 (&(&ip->i_iolock)->mr_lock){----}: > [<ffffffff80278f4d>] __lock_acquire+0xbdd/0x1020 > [<ffffffff802793f5>] lock_acquire+0x65/0x90 > [<ffffffff8026d746>] down_write_nested+0x46/0x80 > [<ffffffff8039df29>] xfs_ilock+0x99/0xa0 > [<ffffffff8039e0cf>] xfs_ireclaim+0x3f/0x90 > [<ffffffff803ba889>] xfs_finish_reclaim+0x59/0x1a0 > [<ffffffff803bc199>] xfs_reclaim+0x109/0x110 > [<ffffffff803c9541>] xfs_fs_clear_inode+0xe1/0x110 > [<ffffffff802d906d>] clear_inode+0x7d/0x110 > [<ffffffff802d93aa>] dispose_list+0x2a/0x100 > [<ffffffff802d96af>] shrink_icache_memory+0x22f/0x290 > [<ffffffff8029d868>] shrink_slab+0x168/0x1d0 > [<ffffffff8029e0b6>] kswapd+0x3b6/0x560 > [<ffffffff8026921d>] kthread+0x4d/0x80 > [<ffffffff80227428>] child_rip+0xa/0x12 > [<ffffffffffffffff>] 0xffffffffffffffff
You may as well ignore anything invlving this path in XFS until lockdep gets fixed. The kswapd reclaim path is inverted over the synchronous reclaim path that is xfs_ilock -> run out of memory -> prune_icache and then potentially another -> xfs_ilock.
In this case, XFS can *never* deadlock because the second xfs_ilock is on a different, unreferenced, unlocked inode, but without turning off lockdep there is nothing in XFS that can be done to prevent this warning.
Therxp eis a similar bug in the VM w.r.t the mmap_sem in that the mmap_sem is held across a call to put_filp() which can result in inversions between the xfs_ilock and mmap_sem.
Both of these cases cannot be solved by changing XFS - lockdep needs to be made aware of paths that can invert normal locking order (like prune_icache) so it doesn't give false positives like this.
> -> #0 (iprune_mutex){--..}: > [<ffffffff80278db7>] __lock_acquire+0xa47/0x1020 > [<ffffffff802793f5>] lock_acquire+0x65/0x90 > [<ffffffff805dedd5>] mutex_lock_nested+0xb5/0x300 > [<ffffffff802d94fd>] shrink_icache_memory+0x7d/0x290 > [<ffffffff8029d868>] shrink_slab+0x168/0x1d0 > [<ffffffff8029db38>] try_to_free_pages+0x268/0x3a0 > [<ffffffff802979d6>] __alloc_pages_internal+0x206/0x4b0 > [<ffffffff80297c89>] __alloc_pages_nodemask+0x9/0x10 > [<ffffffff802b2bc2>] alloc_page_vma+0x72/0x1b0 > [<ffffffff802a3642>] handle_mm_fault+0x462/0x7b0 > [<ffffffff805e3ecc>] do_page_fault+0x30c/0x890 > [<ffffffff805e16cd>] error_exit+0x0/0xa9 > [<ffffffffffffffff>] 0xffffffffffffffff
This case is different in that it įs complaining about mmap_sem vs iprune_mutex, so I think that we can pretty much ignore the XFS side of things here - the problem is higher level code....
> [<ffffffff8029db38>] try_to_free_pages+0x268/0x3a0 > [<ffffffff8029c240>] ? isolate_pages_global+0x0/0x40 > [<ffffffff802979d6>] __alloc_pages_internal+0x206/0x4b0 > [<ffffffff80297c89>] __alloc_pages_nodemask+0x9/0x10 > [<ffffffff802b2bc2>] alloc_page_vma+0x72/0x1b0 > [<ffffffff802a3642>] handle_mm_fault+0x462/0x7b0
FWIW, should page allocation in a page fault be allowed to recurse into the filesystem? If I follow the spaghetti of inline and compiler inlined functions correctly, this is a GFP_HIGHUSER_MOVABLE allocation, right? Should we be allowing shrink_icache_memory() to be called at all in the page fault path?
Cheers,
Dave. -- Dave Chinner david@fromorbit.com -- 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/
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