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. 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>
