On 05/12/2013 06:27 AM, tip-bot for Thomas Gleixner wrote: > Commit-ID: 4b0c0f294f60abcdd20994a8341a95c8ac5eeb96 > Gitweb: http://git.kernel.org/tip/4b0c0f294f60abcdd20994a8341a95c8ac5eeb96 > Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > AuthorDate: Fri, 3 May 2013 15:02:50 +0200 > Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > CommitDate: Sun, 12 May 2013 12:20:09 +0200 > > tick: Cleanup NOHZ per cpu data on cpu down > > Prarit reported a crash on CPU offline/online. The reason is that on > CPU down the NOHZ related per cpu data of the dead cpu is not cleaned > up. If at cpu online an interrupt happens before the per cpu tick > device is registered the irq_enter() check potentially sees stale data > and dereferences a NULL pointer. > > Cleanup the data after the cpu is dead. Thomas, while this does fix up the NULL pointer issue, I think you've introduced a new bug in the schedule timer code. While doing up and downs on the same CPU, I now occasionally see long delays in the up and down... [ 65.150073] smpboot: Booting Node 1 Processor 19 APIC 0x28 [ 66.715339] smpboot: CPU 19 is now offline [ 67.752751] smpboot: Booting Node 1 Processor 19 APIC 0x28 [ 68.758711] smpboot: CPU 19 is now offline Everything is normal ... [ 69.711612] smpboot: Booting Node 1 Processor 19 APIC 0x28 [ 70.731521] smpboot: CPU 19 is now offline Long delay in bringing CPU "down" [ 81.744565] smpboot: Booting Node 1 Processor 19 APIC 0x28 [ 82.848591] smpboot: CPU 19 is now offline Long delay in bringing CPU "up" [ 89.826533] smpboot: Booting Node 1 Processor 19 APIC 0x28 [ 84.905358] smpboot: CPU 19 is now offline [ 87.565274] smpboot: Booting Node 1 Processor 19 APIC 0x28 Also, if the system is in this state I cannot reboot -- the system appears to hang while bringing down CPUs... Oddly, if I do + memset(ts, 0, sizeof(*ts)); + ts->tick_stopped = 1; instead of your memset, everything works. I'm looking at the tick-sched.c code to see why setting tick_stopped = 1 seems to fix the problem. P. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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