On Tue, Dec 19, 2017 at 3:40 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > On Tue, Dec 19, 2017 at 3:27 PM, Tetsuo Handa > <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: >> syzbot wrote: >>> >>> syzkaller has found reproducer for the following crash on >>> f3b5ad89de16f5d42e8ad36fbdf85f705c1ae051 >> >> "BUG: workqueue lockup" is not a crash. > > Hi Tetsuo, > > What is the proper name for all of these collectively? > > >>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master >>> compiler: gcc (GCC) 7.1.1 20170620 >>> .config is attached >>> Raw console output is attached. >>> C reproducer is attached >>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ >>> for information about syzkaller reproducers >>> >>> >>> BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 37s! >>> BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=-20 stuck for 32s! >>> Showing busy workqueues and worker pools: >>> workqueue events: flags=0x0 >>> pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 >>> pending: cache_reap >>> workqueue events_power_efficient: flags=0x80 >>> pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 >>> pending: neigh_periodic_work, do_cache_clean >>> workqueue mm_percpu_wq: flags=0x8 >>> pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 >>> pending: vmstat_update >>> workqueue kblockd: flags=0x18 >>> pwq 3: cpus=1 node=0 flags=0x0 nice=-20 active=1/256 >>> pending: blk_timeout_work >> >> You gave up too early. There is no hint for understanding what was going on. >> While we can observe "BUG: workqueue lockup" under memory pressure, there is >> no hint like SysRq-t and SysRq-m. Thus, I can't tell something is wrong. > > Do you know how to send them programmatically? I tried to find a way > several times, but failed. Articles that I've found talk about > pressing some keys that don't translate directly to us-ascii. On second though, some oopses automatically dump locks/tasks. Should we do the same for this oops? > But you can also run the reproducer. No report can possible provide > all possible useful information, sometimes debugging boils down to > manually adding printfs. That's why syzbot aims at providing a > reproducer as the ultimate source of details. Also since a developer > needs to test a proposed fix, it's easier to start with the reproducer > right away. > > >> At least you need to confirm that lockup lasts for a few minutes. Otherwise, > > Is it possible to increase the timeout? How? We could bump it up to 2 minutes. > > >> this might be just overstressing. (According to repro.c , 12 threads are >> created and soon SEGV follows? According to above message, only 2 CPUs? >> Triggering SEGV suggests memory was low due to saving coredump?) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
