From: Dmitry Adamushko Date: Mon, 30 Jun 2008 16:22:34 +0000 (+0200) Subject: sched: fix cpu hotplug X-Git-Tag: v2.6.25.10~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0758c2f30b75419fbe5e0ec6dfc892bbc0687f57;p=thirdparty%2Fkernel%2Fstable.git sched: fix cpu hotplug Commit 79c537998d143b127c8c662a403c3356cb885f1c upstream the CPU hotplug problems (crashes under high-volume unplug+replug tests) seem 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) Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/sched.c b/kernel/sched.c index 1e4596c68dd0b..c54077ca1ed16 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5728,6 +5728,7 @@ 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); }