perf_counter: x86: self-IPI for pending work

Implement set_perf_counter_pending() with a self-IPI so that it will
run ASAP in a usable context.

For now use a second IRQ vector, because the primary vector pokes
the apic in funny ways that seem to confuse things.

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: <20090406094517.724626696@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/include/asm/perf_counter.h b/arch/x86/include/asm/perf_counter.h
index e2b0e66b2353..d08dd52cb8ff 100644
--- a/arch/x86/include/asm/perf_counter.h
+++ b/arch/x86/include/asm/perf_counter.h
@@ -84,7 +84,8 @@ union cpuid10_edx {
 #define MSR_ARCH_PERFMON_FIXED_CTR2                     0x30b
 #define X86_PMC_IDX_FIXED_BUS_CYCLES                    (X86_PMC_IDX_FIXED + 2)
 
-#define set_perf_counter_pending()      do { } while (0)
+extern void set_perf_counter_pending(void);
+
 #define clear_perf_counter_pending()    do { } while (0)
 #define test_perf_counter_pending()     (0)