From: Ingo Molnar Date: Mon, 8 Dec 2008 13:20:16 +0000 (+0100) Subject: x86, perfcounters: read out MSR_CORE_PERF_GLOBAL_STATUS with counters disabled X-Git-Tag: v2.6.31-rc1~383^2~587 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=87b9cf4623ad4e5fc009e48c020593dffd5d3793;p=karo-tx-linux.git x86, perfcounters: read out MSR_CORE_PERF_GLOBAL_STATUS with counters disabled Impact: make perfcounter NMI and IRQ sequence more robust Make __smp_perf_counter_interrupt() a bit more conservative: first disable all counters, then read out the status. Most invocations are because there are real events, so there's no performance impact. Code flow gets a bit simpler as well this way. Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 82440cbed0e6..615e953208ef 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -383,18 +383,16 @@ static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi) struct cpu_hw_counters *cpuc; u64 ack, status; - rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status); - if (!status) { - ack_APIC_irq(); - return; - } - /* Disable counters globally */ wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0, 0); ack_APIC_irq(); cpuc = &per_cpu(cpu_hw_counters, cpu); + rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status); + if (!status) + goto out; + again: ack = status; for_each_bit(bit, (unsigned long *) &status, nr_hw_counters) { @@ -440,7 +438,7 @@ again: rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status); if (status) goto again; - +out: /* * Do not reenable when global enable is off: */