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perfcounters, x86: simplify disable/enable of counters

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Impact: fix spurious missed counter wakeups

In the case of NMI events, close a race window that can occur if an NMI
hits counter code that temporarily disables+enables a counter, and the NMI
leaks into the disabled section.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-12-09 11:40:46 +01:00
parent 4c59e4676d
commit 7e2ae34749
1 changed files with 28 additions and 12 deletions
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38
arch/x86/kernel/cpu/perf_counter.c
View file

@ -136,14 +136,25 @@ void hw_perf_disable_all(void)
wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0, 0);
}
static inline void
__hw_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx)
{
wrmsr(hwc->config_base + idx, hwc->config, 0);
}
static DEFINE_PER_CPU(u64, prev_next_count[MAX_HW_COUNTERS]);
static void __hw_perf_counter_enable(struct hw_perf_counter *hwc, int idx)
static void __hw_perf_counter_set_period(struct hw_perf_counter *hwc, int idx)
{
per_cpu(prev_next_count[idx], smp_processor_id()) = hwc->next_count;
wrmsr(hwc->counter_base + idx, hwc->next_count, 0);
wrmsr(hwc->config_base + idx, hwc->config, 0);
}
static void __hw_perf_counter_enable(struct hw_perf_counter *hwc, int idx)
{
wrmsr(hwc->config_base + idx,
hwc->config | ARCH_PERFMON_EVENTSEL0_ENABLE, 0);
}
void hw_perf_counter_enable(struct perf_counter *counter)
@ -161,11 +172,11 @@ void hw_perf_counter_enable(struct perf_counter *counter)
perf_counters_lapic_init(hwc->nmi);
wrmsr(hwc->config_base + idx,
hwc->config & ~ARCH_PERFMON_EVENTSEL0_ENABLE, 0);
__hw_perf_counter_disable(hwc, idx);
cpuc->counters[idx] = counter;
counter->hw.config |= ARCH_PERFMON_EVENTSEL0_ENABLE;
__hw_perf_counter_set_period(hwc, idx);
__hw_perf_counter_enable(hwc, idx);
}
@ -286,8 +297,7 @@ void hw_perf_counter_disable(struct perf_counter *counter)
struct hw_perf_counter *hwc = &counter->hw;
unsigned int idx = hwc->idx;
counter->hw.config &= ~ARCH_PERFMON_EVENTSEL0_ENABLE;
wrmsr(hwc->config_base + idx, hwc->config, 0);
__hw_perf_counter_disable(hwc, idx);
clear_bit(idx, cpuc->used);
cpuc->counters[idx] = NULL;
@ -328,19 +338,25 @@ static void perf_store_irq_data(struct perf_counter *counter, u64 data)
}
}
/*
* NMI-safe enable method:
*/
static void perf_save_and_restart(struct perf_counter *counter)
{
struct hw_perf_counter *hwc = &counter->hw;
int idx = hwc->idx;
u64 pmc_ctrl;
int err;
wrmsr(hwc->config_base + idx,
hwc->config & ~ARCH_PERFMON_EVENTSEL0_ENABLE, 0);
err = rdmsrl_safe(MSR_ARCH_PERFMON_EVENTSEL0 + idx, &pmc_ctrl);
WARN_ON_ONCE(err);
if (hwc->config & ARCH_PERFMON_EVENTSEL0_ENABLE) {
__hw_perf_save_counter(counter, hwc, idx);
__hw_perf_counter_set_period(hwc, idx);
if (pmc_ctrl & ARCH_PERFMON_EVENTSEL0_ENABLE)
__hw_perf_counter_enable(hwc, idx);
}
}
static void
perf_handle_group(struct perf_counter *leader, u64 *status, u64 *overflown)