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perf_counter: fix nmi-watchdog interaction 

When we don't have any perf-counters active, don't act like we know
what the NMI is for.

[ Impact: fix hard hang with nmi_watchdog=2 ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090501102533.109867793@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-05-01 12:23:17 +02:00 committed by Ingo Molnar
parent c33a0bc4e4
commit 63a809a2dc
1 changed files with 3 additions and 0 deletions
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3
arch/x86/kernel/cpu/perf_counter.c
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@ -871,6 +871,9 @@ perf_counter_nmi_handler(struct notifier_block *self,
struct pt_regs *regs; struct pt_regs *regs;
int ret; int ret;
if (!atomic_read(&num_counters))
return NOTIFY_DONE;
switch (cmd) { switch (cmd) {
case DIE_NMI: case DIE_NMI:
case DIE_NMI_IPI: case DIE_NMI_IPI: