Messages in this thread | | | Date | Thu, 28 May 2009 11:36:08 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH 0/11] Per-bdi writeback flusher threads v8 |
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On Thu, May 28 2009, Jan Kara wrote: > On Wed 27-05-09 20:49:59, Theodore Tso wrote: > > On Wed, May 27, 2009 at 09:45:43PM +0200, Jens Axboe wrote: > > > > > > This one has been tested good, where good means that it boots and > > > functions normally at least. Whether it fixes your issue, that would be > > > interesting to know :-) > > > > > > > Unfortunately, it doesn't seem to have. Here's a dmesg with the > > softlockup report and the sysrq-t output. Unfortunately the dmesg > > file is too big for LKML, so I've compressed it so you can get the > > whole thing. > Everybody waits for sys_sync() to complete and they never seem to be > woken up. Jens, wb_work_complete() seems a bit fishy - who does > wb_clear_work() in sync_mode == WB_SYNC_ALL which is on stack?
It is tricky, I looked through that several times. I think wb_work_complete() should do:
if (!bdi_work_on_stack(work)) bdi_work_clear(work); if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work)) call_rcu(&work->rcu_head, bdi_work_free);
to have bdi_work_clear() called for the on-stack work. I'll double check this and roll out a new release, once tested. I haven't been able to reproduce Ted's problem yet, but perhaps my bdi_alloc() test failures haven't triggered for WB_SYNC_ALL yet.
> > There's also a lockdep warning which fsx triggered. > The lockdep warning is definitely unrelated. It's really a possible > deadlock, although not quite probable. IMHO the problem is that > sysfs_mutex gets above mmap_sem due to code in sysfs_readdir which calls > filldir() which may cause page fault. At the same time it gets quite low > on the lock stack because filesystems call sysfs functions from their > internal functions (in this case ext4_put_super) holding quite some locks. > Adding a few CC's for this.
Thanks, I didn't see any bdi related stuff in there either.
-- Jens Axboe
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