Messages in this thread | | | Date | Tue, 01 Jul 2008 17:22:56 +0800 | From | Lai Jiangshan <> | Subject | Re: [BUG] CFS vs cpu hotplug |
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Ingo Molnar wrote: > * Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > >> On Sun, Jun 29, 2008 at 12:16:56AM +0200, Dmitry Adamushko wrote: >>> Hello, >>> >>> >>> it seems to be related to migrate_dead_tasks(). >>> >>> Firstly I added traces to see all tasks being migrated with >>> migrate_live_tasks() and migrate_dead_tasks(). On my setup the problem >>> pops up (the one with "se == NULL" in the loop of >>> pick_next_task_fair()) shortly after the traces indicate that some has >>> been migrated with migrate_dead_tasks()). btw., I can reproduce it >>> much faster now with just a plain cpu down/up loop. >>> >>> [disclaimer] Well, unless I'm really missing something important in >>> this late hour [/desclaimer] pick_next_task() is not something >>> appropriate for migrate_dead_tasks() :-) >>> >>> the following change seems to eliminate the problem on my setup >>> (although, I kept it running only for a few minutes to get a few >>> messages indicating migrate_dead_tasks() does move tasks and the >>> system is still ok) >>> >>> [ quick hack ] >>> >>> @@ -5887,6 +5907,7 @@ static void migrate_dead_tasks(unsigned int dead_cpu) >>> next = pick_next_task(rq, rq->curr); >>> if (!next) >>> break; >>> + next->sched_class->put_prev_task(rq, next); >>> migrate_dead(dead_cpu, next); >>> >>> } >> Thanks Dmitry! With your patch I cannot reproduce the bug anymore. > > thanks - it passed my testing too. It's lined up for v2.6.26 merge, in > tip/sched/urgent. > > Avi, does this patch fix your CPU hotplug problems too? > > Ingo > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > >
Hi, Ingo
The following oops still occurred whether this patch is applied or not.
Lai Jiangshan
------------[ cut here ]------------ kernel BUG at kernel/sched.c:6133! invalid opcode: 0000 [1] SMP CPU 0 Modules linked in: Pid: 4744, comm: cpu_online.sh Not tainted 2.6.26-rc8 #1 RIP: 0010:[<ffffffff8058d0a9>] [<ffffffff8058d0a9>] migration_call+0x3eb/0x494 RSP: 0018:ffff81007115fd28 EFLAGS: 00010202 RAX: ffffffffffffffe3 RBX: ffff810001017580 RCX: 000000801b7c6e42 RDX: ffff81007115fcf8 RSI: 0000009388d2771c RDI: ffff810001017e00 RBP: ffff81007115fd78 R08: ffff81007115e000 R09: ffff8100807d6000 R10: ffff81007fb6d050 R11: 00000000ffffffff R12: 0000000000000283 R13: ffff810001029580 R14: ffff810001029580 R15: 0000000000000002 FS: 00007fbb153d36f0(0000) GS:ffffffff807a3000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007fabafe2b0a8 CR3: 0000000076901000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process cpu_online.sh (pid: 4744, threadinfo ffff81007115e000, task ffff810071447200) Stack: ffff81007115e000 000000007115fbd8 00000000ffffffff 0000000000000002 ffff81007115fd78 0000000000000000 00000000ffffffff ffffffff807a1d40 0000000000000002 0000000000000007 ffff81007115fdb8 ffffffff8059372c Call Trace: [<ffffffff8059372c>] notifier_call_chain+0x33/0x5b [<ffffffff802476a9>] __raw_notifier_call_chain+0x9/0xb [<ffffffff802476ba>] raw_notifier_call_chain+0xf/0x11 [<ffffffff805736d6>] _cpu_down+0x191/0x256 [<ffffffff805737c1>] cpu_down+0x26/0x36 [<ffffffff805749c1>] store_online+0x32/0x75 [<ffffffff803d1982>] sysdev_store+0x24/0x26 [<ffffffff802d2551>] sysfs_write_file+0xe0/0x11c [<ffffffff80290e6b>] vfs_write+0xae/0x137 [<ffffffff802913d3>] sys_write+0x47/0x70 [<ffffffff8020b1eb>] system_call_after_swapgs+0x7b/0x80
Code: 80 07 00 00 48 01 83 80 07 00 00 49 c7 85 80 07 00 00 00 00 00 00 41 fe 45 00 49 39 dd 74 02 fe 03 41 54 9d 49 83 7d 08 00 74 04 <0f> 0b eb fe 4c 89 ef e8 b8 40 00 00 eb 1e 48 8b 11 48 8b 41 08 RIP [<ffffffff8058d0a9>] migration_call+0x3eb/0x494 RSP <ffff81007115fd28> ---[ end trace f22fd757d4f07850 ]---
platform: x86_64 2cores*2cpus fedora9 # cat cpu_online.sh #!/bin/sh
cpu1=1 cpu2=1 cpu3=1 while ((1)) do no=$(($RANDOM % 3 + 1)) if ((!cpu$no)) then echo 1 > /sys/devices/system/cpu/cpu$no/online ((cpu$no=1)) else echo 0 > /sys/devices/system/cpu/cpu$no/online ((cpu$no=0)) fi echo 1 $cpu1 $cpu2 $cpu3 sleep 2 done
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