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Commit f5a5a2f6 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

perf_counter: x86: Fix throttling 



If counters are disabled globally when a perfcounter IRQ/NMI hits,
and if we throttle in that case, we'll promote the '0' value to
the next lapic IRQ and disable all perfcounters at that point,
permanently ...

Fix it.

[ Impact: fix hung perfcounters under load ]

Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ec3232bd

arch/x86/kernel/cpu/perf_counter.c

+15 −5
Original line number Diff line number Diff line
@@ -765,8 +765,13 @@ static int intel_pmu_handle_irq(struct pt_regs *regs, int nmi) 
	/*

	 * Restore - do not reenable when global enable is off or throttled:

	 */

	if (++cpuc->interrupts < PERFMON_MAX_INTERRUPTS)

	if (cpuc->throttle_ctrl) {

		if (++cpuc->interrupts < PERFMON_MAX_INTERRUPTS) {

			intel_pmu_restore_all(cpuc->throttle_ctrl);

		} else {

			pr_info("CPU#%d: perfcounters: max interrupt rate exceeded! Throttle on.\n", smp_processor_id());

		}

	}



	return ret;

}
@@ -817,12 +822,17 @@ void perf_counter_unthrottle(void) 


	cpuc = &__get_cpu_var(cpu_hw_counters);

	if (cpuc->interrupts >= PERFMON_MAX_INTERRUPTS) {

		if (printk_ratelimit())

			printk(KERN_WARNING "perfcounters: max interrupts exceeded!\n");

		pr_info("CPU#%d: perfcounters: throttle off.\n", smp_processor_id());



		/*

		 * Clear them before re-enabling irqs/NMIs again:

		 */

		cpuc->interrupts = 0;

		hw_perf_restore(cpuc->throttle_ctrl);

	}

	} else {

		cpuc->interrupts = 0;

	}

}



void smp_perf_counter_interrupt(struct pt_regs *regs)

{