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Subject[PATCH -tip] perf_counter/x86: Always use NMI for performance-monitoring interrupt
Always use NMI for performance-monitoring interrupt as there could be
racy situations if we switch between irq and nmi mode frequently.

Signed-off-by: Yong Wang <yong.y.wang@intel.com>

---
include/asm/perf_counter.h | 4 ++--
kernel/apic/apic.c | 2 +-
kernel/cpu/perf_counter.c | 19 +++++--------------
3 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/perf_counter.h b/arch/x86/include/asm/perf_counter.h
index d08dd52..876ed97 100644
--- a/arch/x86/include/asm/perf_counter.h
+++ b/arch/x86/include/asm/perf_counter.h
@@ -91,10 +91,10 @@ extern void set_perf_counter_pending(void);

#ifdef CONFIG_PERF_COUNTERS
extern void init_hw_perf_counters(void);
-extern void perf_counters_lapic_init(int nmi);
+extern void perf_counters_lapic_init(void);
#else
static inline void init_hw_perf_counters(void) { }
-static inline void perf_counters_lapic_init(int nmi) { }
+static inline void perf_counters_lapic_init(void) { }
#endif

#endif /* _ASM_X86_PERF_COUNTER_H */
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 749fae9..622d11a 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1189,7 +1189,7 @@ void __cpuinit setup_local_APIC(void)
apic_write(APIC_ESR, 0);
}
#endif
- perf_counters_lapic_init(0);
+ perf_counters_lapic_init();

preempt_disable();

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 2eeaa99..316b0c9 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -604,7 +604,7 @@ try_generic:
hwc->counter_base = x86_pmu.perfctr;
}

- perf_counters_lapic_init(hwc->nmi);
+ perf_counters_lapic_init();

x86_pmu.disable(hwc, idx);

@@ -863,24 +863,15 @@ void set_perf_counter_pending(void)
apic->send_IPI_self(LOCAL_PENDING_VECTOR);
}

-void perf_counters_lapic_init(int nmi)
+void perf_counters_lapic_init(void)
{
- u32 apic_val;
-
if (!x86_pmu_initialized())
return;

/*
- * Enable the performance counter vector in the APIC LVT:
+ * Always use NMI for PMU
*/
- apic_val = apic_read(APIC_LVTERR);
-
- apic_write(APIC_LVTERR, apic_val | APIC_LVT_MASKED);
- if (nmi)
- apic_write(APIC_LVTPC, APIC_DM_NMI);
- else
- apic_write(APIC_LVTPC, LOCAL_PERF_VECTOR);
- apic_write(APIC_LVTERR, apic_val);
+ apic_write(APIC_LVTPC, APIC_DM_NMI);
}

static int __kprobes
@@ -1054,7 +1045,7 @@ void __init init_hw_perf_counters(void)

pr_info("... counter mask: %016Lx\n", perf_counter_mask);

- perf_counters_lapic_init(0);
+ perf_counters_lapic_init();
register_die_notifier(&perf_counter_nmi_notifier);
}


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