On Tue, Jul 04, 2017 at 07:44:58PM +0530, Abdul Haleem wrote: > On Fri, 2017-06-30 at 17:28 +1000, Nicholas Piggin wrote: > > On Fri, 30 Jun 2017 10:52:18 +0530 > > Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx> wrote: > > > > > On Fri, 2017-06-30 at 00:45 +1000, Nicholas Piggin wrote: > > > > On Thu, 29 Jun 2017 20:23:05 +1000 > > > > Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > > > > > > > > On Thu, 29 Jun 2017 19:36:14 +1000 > > > > > Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > > > > > > > > > I don't *think* the replay-wakeup-interrupt patch is directly involved, but > > > > > > it's likely to be one of the idle patches. > > > > > > > > Okay this turned out to be misconfigured sleep states I added for the > > > > simulator, sorry for the false alarm. > > > > > > > > > Although you have this in the backtrace. I wonder if that's a stuck > > > > > lock in rcu_process_callbacks? > > > > > > > > So this spinlock becomes top of the list of suspects. Can you try > > > > enabling lockdep and try to reproduce it? > > > > > > Yes, recreated again with CONFIG_LOCKDEP=y & CONFIG_DEBUG_LOCKDEP=y set. > > > I do not see any difference in trace messages with and without LOCKDEP > > > enabled. > > > > > > Please find the attached log file. > > > > Can you get an rcu_invoke_callback event trace that Paul suggested? > > I could not reproduce the issue with the latest next kernel > (4.12.0-rc7-next-20170703). > > > Does this bug show up with just the powerpc next branch? > > Perhaps, stress-ng test on today's mainline kernel (4.12.0) triggered a > different trace message and this not reproducible all the time. > > > stress-ng --io 100 --vm 10 --vm-bytes 100g --timeout 1h --oomable > > INFO: rcu_sched self-detected stall on CPU > 8-...: (2099 ticks this GP) idle=37e/140000000000001/0 > softirq=1404131/1404131 fqs=932 > (t=2100 jiffies g=394894 c=394893 q=21997) > Task dump for CPU 8: > kworker/u162:2 R running task 11168 28468 2 0x00000884 > Workqueue: writeback wb_workfn (flush-253:1) > Call Trace: > [c00000036e3eb340] [c000000000114480] sched_show_task+0xf0/0x160 > (unreliable) > [c00000036e3eb3b0] [c0000000009adc2c] rcu_dump_cpu_stacks+0xd0/0x134 > [c00000036e3eb400] [c00000000015e4d0] rcu_check_callbacks+0x8f0/0xaf0 > [c00000036e3eb530] [c000000000165e2c] update_process_times+0x3c/0x90 > [c00000036e3eb560] [c00000000017b73c] tick_sched_handle.isra.13 > +0x2c/0xc0 > [c00000036e3eb590] [c00000000017b828] tick_sched_timer+0x58/0xb0 > [c00000036e3eb5d0] [c0000000001669e8] __hrtimer_run_queues+0xf8/0x330 > [c00000036e3eb650] [c000000000167744] hrtimer_interrupt+0xe4/0x280 > [c00000036e3eb710] [c000000000022620] __timer_interrupt+0x90/0x270 > [c00000036e3eb760] [c000000000022cf0] timer_interrupt+0xa0/0xe0 > [c00000036e3eb790] [c0000000000091e8] decrementer_common+0x158/0x160 > --- interrupt: 901 at move_expired_inodes+0x30/0x200 > LR = queue_io+0x8c/0x190 > [c00000036e3eba80] [c00000036e3ebac0] 0xc00000036e3ebac0 (unreliable) > [c00000036e3ebac0] [c000000000319b24] wb_writeback+0x2b4/0x420 The usual assumption would be that wb_writeback() is looping or... > [c00000036e3ebb90] [c00000000031a980] wb_workfn+0xf0/0x4b0 > [c00000036e3ebca0] [c0000000000fa160] process_one_work+0x180/0x470 > [c00000036e3ebd30] [c0000000000fa6d4] worker_thread+0x284/0x500 ...there is so much work being scheduled that worker_thread() cannot keep up. If tracing locates such a loop, the usual trick is to place a cond_resched_rcu_qs() somewhere in it (but of course not where interrupts or preemption are disabled). Tracing can help detect this. Or printk()s, for that matter. ;-) Thanx, Paul > [c00000036e3ebdc0] [c000000000101fc0] kthread+0x160/0x1a0 > [c00000036e3ebe30] [c00000000000bb60] ret_from_kernel_thread+0x5c/0x7c > INFO: rcu_sched self-detected stall on CPU > 51-...: (2099 ticks this GP) idle=7c2/140000000000001/0 > softirq=1272749/1272749 fqs=995 > (t=2100 jiffies g=394900 c=394899 q=32186) > ~ > > stress-ng : http://kernel.ubuntu.com/git/cking/stress-ng.git > > > > > Thanks, > > Nick > > > > > -- > Regard's > > Abdul Haleem > IBM Linux Technology Centre > > > -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
