Merge git://git.infradead.org/users/dwmw2/mtd-2.6.38

[mv-sheeva.git] / arch / x86 / kernel / cpu / perf_event_p4.c

diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index f7a0993c1e7c7a7a321b9057f9aaad75a75cc611..ff751a9f182b15bcb5ff94a00079c26a3d80229d 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/arch/x86/kernel/cpu/perf_event_p4.c
@@ -770,9 +770,14 @@ static inline int p4_pmu_clear_cccr_ovf(struct hw_perf_event *hwc)
                return 1;
        }
 
-       /* it might be unflagged overflow */
-       rdmsrl(hwc->event_base + hwc->idx, v);
-       if (!(v & ARCH_P4_CNTRVAL_MASK))
+       /*
+        * In some circumstances the overflow might issue an NMI but did
+        * not set P4_CCCR_OVF bit. Because a counter holds a negative value
+        * we simply check for high bit being set, if it's cleared it means
+        * the counter has reached zero value and continued counting before
+        * real NMI signal was received:
+        */
+       if (!(v & ARCH_P4_UNFLAGGED_BIT))
                return 1;
 
        return 0;