From 0db1a7bc00216a981d0b7056627ad8682f4f0636 Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Mon, 17 May 2010 16:13:04 +0800 Subject: [PATCH] perf, x86: P4 PMU -- handle unflagged events It might happen that an event can overflow without the proper overflow flag set. Check the sign bit in the raw counter value to solve this problem. Tested-by: Lin Ming Signed-off-by: Cyrill Gorcunov Cc: Peter Zijlstra Cc: fweisbec@gmail.com Cc: Cyrill Gorcunov Cc: Arnaldo Carvalho de Melo LKML-Reference: <1274083984.6540.15.camel@minggr.sh.intel.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_p4.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c index 424fc8d..02f0728 100644 --- a/arch/x86/kernel/cpu/perf_event_p4.c +++ b/arch/x86/kernel/cpu/perf_event_p4.c @@ -465,15 +465,21 @@ out: return rc; } -static inline void p4_pmu_clear_cccr_ovf(struct hw_perf_event *hwc) +static inline int p4_pmu_clear_cccr_ovf(struct hw_perf_event *hwc) { - unsigned long dummy; + int overflow = 0; + u32 low, high; - rdmsrl(hwc->config_base + hwc->idx, dummy); - if (dummy & P4_CCCR_OVF) { + rdmsr(hwc->config_base + hwc->idx, low, high); + + /* we need to check high bit for unflagged overflows */ + if ((low & P4_CCCR_OVF) || (high & (1 << 31))) { + overflow = 1; (void)checking_wrmsrl(hwc->config_base + hwc->idx, - ((u64)dummy) & ~P4_CCCR_OVF); + ((u64)low) & ~P4_CCCR_OVF); } + + return overflow; } static inline void p4_pmu_disable_event(struct perf_event *event) @@ -584,21 +590,15 @@ static int p4_pmu_handle_irq(struct pt_regs *regs) WARN_ON_ONCE(hwc->idx != idx); - /* - * FIXME: Redundant call, actually not needed - * but just to check if we're screwed - */ - p4_pmu_clear_cccr_ovf(hwc); + /* it might be unflagged overflow */ + handled = p4_pmu_clear_cccr_ovf(hwc); val = x86_perf_event_update(event); - if (val & (1ULL << (x86_pmu.cntval_bits - 1))) + if (!handled && (val & (1ULL << (x86_pmu.cntval_bits - 1)))) continue; - /* - * event overflow - */ - handled = 1; - data.period = event->hw.last_period; + /* event overflow for sure */ + data.period = event->hw.last_period; if (!x86_perf_event_set_period(event)) continue; -- 1.8.2.3