Re: [PATCH v3] bcache: fix deadlock in bcache_allocator
From: Andrea Righi
Date: Thu Oct 10 2019 - 11:21:30 EST
On Wed, Aug 07, 2019 at 09:53:46PM +0800, Coly Li wrote:
> On 2019/8/7 6:38 äå, Andrea Righi wrote:
> > bcache_allocator can call the following:
> > bch_allocator_thread()
> > -> bch_prio_write()
> > -> bch_bucket_alloc()
> > -> wait on &ca->set->bucket_wait
> > But the wake up event on bucket_wait is supposed to come from
> > bch_allocator_thread() itself => deadlock:
> > [ 1158.490744] INFO: task bcache_allocato:15861 blocked for more than 10 seconds.
> > [ 1158.495929] Not tainted 5.3.0-050300rc3-generic #201908042232
> > [ 1158.500653] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > [ 1158.504413] bcache_allocato D 0 15861 2 0x80004000
> > [ 1158.504419] Call Trace:
> > [ 1158.504429] __schedule+0x2a8/0x670
> > [ 1158.504432] schedule+0x2d/0x90
> > [ 1158.504448] bch_bucket_alloc+0xe5/0x370 [bcache]
> > [ 1158.504453] ? wait_woken+0x80/0x80
> > [ 1158.504466] bch_prio_write+0x1dc/0x390 [bcache]
> > [ 1158.504476] bch_allocator_thread+0x233/0x490 [bcache]
> > [ 1158.504491] kthread+0x121/0x140
> > [ 1158.504503] ? invalidate_buckets+0x890/0x890 [bcache]
> > [ 1158.504506] ? kthread_park+0xb0/0xb0
> > [ 1158.504510] ret_from_fork+0x35/0x40
> > Fix by making the call to bch_prio_write() non-blocking, so that
> > bch_allocator_thread() never waits on itself.
> > Moreover, make sure to wake up the garbage collector thread when
> > bch_prio_write() is failing to allocate buckets.
> > BugLink: https://bugs.launchpad.net/bugs/1784665
> > BugLink: https://bugs.launchpad.net/bugs/1796292
> > Signed-off-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx>
> OK, I add this version into my for-test directory. Once you have a new
> version, I will update it. Thanks.
> Coly Li
any news about this patch? We're still using it in Ubuntu and no errors
have been reported so far. Do you think we can add this to linux-next?