Gautham R Shenoy <[EMAIL PROTECTED]> writes: > On Wed, Apr 25, 2007 at 04:54:10PM -0700, Andrew Morton wrote: >> On Thu, 26 Apr 2007 01:10:21 +0200 "Rafael J. Wysocki" <[EMAIL PROTECTED]> >> wrote: >> >> > Hi, >> > >> > The BUG_ON in khthread_bind (line 165 in kthread.c) triggers for me during >> > attempted suspend to disk, when disable_nonboot_cpus() calls _cpu_down() >> > (on x86_64). >> > Caused due to Oleg's patch http://lkml.org/lkml/2007/4/13/93. > > Agreed that most of the time a kthread_create(p) is followed by a > kthread_bind(p), in which case the assertion > WARN_ON(p->state != TASK_UNINTERRUPTIBLE) makes sense. > > But, in cpu hotplug case, we need to rebind the stop_machine_run thread > from the cpu which has just been offlined to any online cpu. > (kernel/cpu.c line 180) > At this point, the thread would be in TASK_INTERRUPTIBLE waiting for us > to call a kthread_stop on it.(kernel/kthread.c line 161) > > We only need to ensure in kthread_bind that the task which is being > bound is not running or exiting. Doesn't matter if it's sleeping in > TASK_INTERRUPTIBLE or TASK_UNINTERRUPTIBLE state.
That will probably handle this problem. However there is a weird interaction with process freezer. The process freezer can come in and wake up a kernel thread to encourage it to call try_to_freeze_process while it is waiting to be bound. How do we handle that evil race? Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
