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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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2
arch/arm/kernel/perf_event.c
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@ -32,7 +32,7 @@ static struct platform_device *pmu_device;
* Hardware lock to serialize accesses to PMU registers. Needed for the
* read/modify/write sequences.
*/
static DEFINE_SPINLOCK(pmu_lock);
static DEFINE_RAW_SPINLOCK(pmu_lock);
/*
* ARMv6 supports a maximum of 3 events, starting from index 1. If we add