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[PATCH] x86: check for online cpus before bringing them up

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Bryce reported a bug wherein offlining CPU0 (on x86 box) and then
subsequently onlining it resulted in a lockup.

On x86, CPU0 is never offlined.  The subsequent attempt to online CPU0
doesn't take that into account.  It actually tries to bootup the already
booted CPU.  Following patch fixes the problem (as acknowledged by Bryce).
Please consider for inclusion in 2.6.16.

Check if cpu is already online.

Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Srivatsa Vaddagiri 2006-03-16 23:04:06 -08:00 committed by Linus Torvalds
parent 8532159f55
commit 82c3c03a40
1 changed files with 10 additions and 0 deletions
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10
arch/i386/kernel/smpboot.c
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@ -1029,6 +1029,16 @@ int __devinit smp_prepare_cpu(int cpu)
int apicid, ret;
lock_cpu_hotplug();
/*
* On x86, CPU0 is never offlined. Trying to bring up an
* already-booted CPU will hang. So check for that case.
*/
if (cpu_online(cpu)) {
ret = -EINVAL;
goto exit;
}
apicid = x86_cpu_to_apicid[cpu];
if (apicid == BAD_APICID) {
ret = -ENODEV;