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ARM: 6521/1: perf: use raw_spinlock_t for pmu_lock

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For kernels built with PREEMPT_RT, critical sections protected
by standard spinlocks are preemptible. This is not acceptable
on perf as (a) we may be scheduled onto a different CPU whilst
reading/writing banked PMU registers and (b) the latency when
reading the PMU registers becomes unpredictable.

This patch upgrades the pmu_lock spinlock to a raw_spinlock
instead.

Reported-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon 2010-12-02 18:01:49 +01:00 • committed by Russell King
parent 4d6b7a779b
commit 961ec6daa7
4 changed files with 35 additions and 35 deletions
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20
arch/arm/kernel/perf_event_v6.c
View file

@ -426,12 +426,12 @@ armv6pmu_enable_event(struct hw_perf_event *hwc,
* Mask out the current event and set the counter to count the event
* that we're interested in.
*/
spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~mask;
val |= evt;
armv6_pmcr_write(val);
spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
}
static irqreturn_t
@ -500,11 +500,11 @@ armv6pmu_start(void)
{
unsigned long flags, val;
spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&pmu_lock, flags);
val = armv6_pmcr_read();
val |= ARMV6_PMCR_ENABLE;
armv6_pmcr_write(val);
spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
}
static void
@ -512,11 +512,11 @@ armv6pmu_stop(void)
{
unsigned long flags, val;
spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~ARMV6_PMCR_ENABLE;
armv6_pmcr_write(val);
spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
}
static int
@ -570,12 +570,12 @@ armv6pmu_disable_event(struct hw_perf_event *hwc,
* of ETM bus signal assertion cycles. The external reporting should
* be disabled and so this should never increment.
*/
spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~mask;
val |= evt;
armv6_pmcr_write(val);
spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
}
static void
@ -599,12 +599,12 @@ armv6mpcore_pmu_disable_event(struct hw_perf_event *hwc,
* Unlike UP ARMv6, we don't have a way of stopping the counters. We
* simply disable the interrupt reporting.
*/
spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~mask;
val |= evt;
armv6_pmcr_write(val);
spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
}
static const struct arm_pmu armv6pmu = {