Commit 82c3c03a authored Mar 16, 2006 by Srivatsa Vaddagiri Committed by Linus Torvalds Mar 17, 2006

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



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>

parent 8532159f

arch/i386/kernel/smpboot.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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;

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