Hi,
>
>On Mon, Sep 19, 2005 at 01:28:38PM +1000, Nigel Cunningham wrote:
>> There is a race condition in taking down a cpu
(kernel/cpu.c::cpu_down).
>> A cpu can already be idling when we clear its online flag, and we do
not
>> force the idle task to reschedule. This results in __cpu_die timing
out.
>
>"when we clear its online flag" - This happens in take_cpu_down in the
>context of stopmachine thread. take_cpu_down also ensures that idle
>thread runs when it returns (sched_idle_next). So when idle thread
runs,
>it should notice that it is offline and invoke play_dead. So I don't
>understand why __cpu_die should time out.
I guess Nigel's point is cpu_idle is preempted before take_cpu_down. If
the preempt occurs after the cpu_is_offline check, when the cpu (after
sched_idle_next) goes into idle again, nobody can wake it up. Nigel,
isn't it?
Thanks,
Shaohua
-
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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
| |
 |