On 04/09/2015 04:23 PM, Mike Galbraith wrote: > On Thu, 2015-04-09 at 16:05 +0200, Sebastian Andrzej Siewior wrote: >> * Mike Galbraith | 2015-03-24 08:14:49 [+0100]: >> >>> do_set_cpus_allowed() is not safe vs ->sched_class change. >>> >>> crash> bt >>> PID: 11676 TASK: ffff88026f979da0 CPU: 22 COMMAND: >>> "sync_unplug/22" >>> #0 [ffff880274d25bc8] machine_kexec at ffffffff8103b41c >>> #1 [ffff880274d25c18] crash_kexec at ffffffff810d881a >>> #2 [ffff880274d25cd8] oops_end at ffffffff81525818 >>> #3 [ffff880274d25cf8] do_invalid_op at ffffffff81003096 >>> #4 [ffff880274d25d90] invalid_op at ffffffff8152d3de >>> [exception RIP: set_cpus_allowed_rt+18] >>> RIP: ffffffff8109e012 RSP: ffff880274d25e48 RFLAGS: 00010202 >>> RAX: ffffffff8109e000 RBX: ffff88026f979da0 RCX: >>> ffff8802770cb6e8 >>> RDX: 0000000000000000 RSI: ffffffff81add700 RDI: >>> ffff88026f979da0 >>> RBP: ffff880274d25e78 R8: ffffffff816112e0 R9: >>> 0000000000000001 >>> R10: 0000000000000001 R11: 0000000000011940 R12: >>> ffff88026f979da0 >>> R13: ffff8802770cb6d0 R14: ffff880274d25fd8 R15: >>> 0000000000000000 >>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >>> #5 [ffff880274d25e60] do_set_cpus_allowed at ffffffff8108e65f >>> #6 [ffff880274d25e80] sync_unplug_thread at ffffffff81058c08 >>> #7 [ffff880274d25ed8] kthread at ffffffff8107cad6 >>> #8 [ffff880274d25f50] ret_from_fork at ffffffff8152bbbc >>> crash> task_struct ffff88026f979da0 | grep class >>> sched_class = 0xffffffff816111e0 <fair_sched_class+64>, >> >> Is this a one-time thing or can you reproduce this? > > Well, I can't reproduce it now, having fixed it ;-) Dunno how > repeatable it would be if I un-fixed it. > >> What happen here? I doubt p vanished. +18 is mostlikely the >> "migrate_disabled_updated()" check. >> >> I doubt p->sched_class->set_cpus_allowed or p->sched_class vanish >> between testing for it and invoking it, or did it? > > Class changed under us. We saw rt task, called rt method, rt method > said BUG_ON(!rt_task(p)), as task had become fair class. but why does backtrace then end in do_set_cpus_allowed and not in set_cpus_allowed_rt()? Is it possible to provide a backtrace which ends in the BUG() statement in set_cpus_allowed_rt() if this is where it is coming from? > -Mike Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
