From: tip-bot for Jacob Pan on
Commit-ID: ae7c9b70dcb4313ea3dbcc9a2f240dae6c2b50c0
Author: Jacob Pan <jacob.jun.pan(a)>
AuthorDate: Mon, 19 Apr 2010 11:23:43 -0700
Committer: H. Peter Anvin <hpa(a)>
CommitDate: Tue, 20 Apr 2010 14:38:28 -0700

x86, mrst: Conditionally register cpu hotplug notifier for apbt

APB timer is used on Moorestown platforms but not on a standard PC.
If APB timer code is compiled in but not initialized at run-time due
to lack of FW reported SFI table, kernel would panic when the non-boot
CPUs are offlined and notifier is called.

This patch ensures CPU hotplug notifier for APB timer is only registered
when the APBT timer block is initialized.

Signed-off-by: Jacob Pan <jacob.jun.pan(a)>
LKML-Reference: <1271701423-1162-1-git-send-email-jacob.jun.pan(a)>
Signed-off-by: H. Peter Anvin <hpa(a)>
arch/x86/kernel/apb_timer.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apb_timer.c b/arch/x86/kernel/apb_timer.c
index ff469e4..a353475 100644
--- a/arch/x86/kernel/apb_timer.c
+++ b/arch/x86/kernel/apb_timer.c
@@ -429,7 +429,7 @@ static int apbt_cpuhp_notify(struct notifier_block *n,

static __init int apbt_late_init(void)
- if (disable_apbt_percpu)
+ if (disable_apbt_percpu || !apb_timer_block_enabled)
return 0;
/* This notifier should be called after workqueue is ready */
hotcpu_notifier(apbt_cpuhp_notify, -20);
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