On Tue, Nov 11, 2008 at 12:31:34PM +0100, Heiko Carstens wrote: > On Tue, Nov 11, 2008 at 11:52:14AM +0100, Ingo Molnar wrote: > > > > * Rafael J. Wysocki <rjw@xxxxxxx> wrote: > > > > > However, it is reproducible by doing > > > > > > # echo core > /sys/power/pm_test > > > > > > and repeating > > > > > > # echo disk > /sys/power/state > > > > > > for a couple of times, in which case the last two lines printed to the console > > > before a (solid) hang are: > > > > > > SMP alternatives: switching to SMP code > > > Booting processor 1 APIC 0x1 ip 0x6000 > > > > > > So, it evidently fails while re-enabling the non-boot CPU and not > > > during disabling it as I thought before. > > > > > > With commit c9583e55fa2b08a230c549bd1e3c0bde6c50d9cc reverted the > > > issue is not reproducible any more. > > > > [ Cc:-ed workqueue/locking/suspend-race-condition experts. ] > > > > Seems like the new kernel/stop_machine.c logic has a race for the test > > sequence above. (Below is the bisected commit again, maybe the race is > > visible via email review as well.) > > FWIW, I tried to reproduce this on s390 and got the following: > > A process that would do nothing but onlining/offlining cpus would get > stuck after a while: > > 0 schedule+842 [0x342522] > 1 schedule_timeout+200 [0x342ec4] > 2 wait_for_common+362 [0x341fd6] > 3 wait_for_completion+54 [0x342146] > 4 __synchronize_sched+80 [0x81670] > 5 cpu_down+172 [0x33c030] > 6 store_online+96 [0x33c488] > 7 sysdev_store+52 [0x1bda84] > 8 sysfs_write_file+242 [0x1350ba] > 9 vfs_write+176 [0xd2028] > 10 sys_write+82 [0xd21ea] > 11 sysc_noemu+16 [0x269d8] > > All cpus are in cpu_idle and no other task in state TASK_INTERRUPTIBLE > or TASK_UNINTERRUPTIBLE. However it would continue to work as soon as > I login into the system or generate a console interrupt. > I'm going to look into the dump and see if I can figure out what is > broken here. > Dunno if it is the same bug or something else. [Cc:-ed Steven and Paul, since this backtrace seems to be RCU specific] Steven, Paul, any idea what could cause the hang? I think I would get lost in the RCU code... -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
