On 2019/10/10 11:21 下午, Andrea Righi wrote: > On Wed, Aug 07, 2019 at 09:53:46PM +0800, Coly Li wrote: >> On 2019/8/7 6:38 下午, 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 > > Hi Coly, > > any news about this patch? We're still using it in Ubuntu and no errors It has been testing on your side for quite long time, and I don't have better idea on the fix. It looks solid enough, and indeed I have it in my development patches already with more testing. > have been reported so far. Do you think we can add this to linux-next? Yes, this is my plan. It is in my testing queue with other developing patches. Thanks. -- Coly Li
