On Tue 02-02-16 15:44:24, Mike Galbraith wrote: > Hi Tejun, > > I'm looking at a crash analysis that fingers 874bbfe6 as being the > culprit. (I didn't do the analysis, but it appears to be correct) > > Scenario: CPU168 calls mod_delayed_work(), is taken offline before the > timer expires. Due to 874bbfe6, dwork->cpu is the now offline CPU168 > vs the previous WORK_CPU_UNBOUND, timer fires on CPU131, it tries to > __queue_work() with cpu == the now offline CPU168, gets to... > > } else > pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); > > ... and goes boom. > > <snippet> > crash> p numa_node | grep 168 > [168]: ffff8c03fdf0e328 > crash> rd ffff8c03fdf0e328 > ffff8c03fdf0e328: 00000000ffffffff ........ > > Thus, pwq becomes 000000000. Then, as the result of reference to > pwq->pool, NULL reference occurs at (*PANIC). > </snippet> > > What if anything is supposed to prevent this?
AFAICS [1] nothing... --- [1] http://lkml.kernel.org/r/20160203122855.gb6...@dhcp22.suse.cz -- Michal Hocko SUSE Labs
