From: Will Deacon <will.deacon@arm.com>
Date: Thu, 2 Dec 2010 17:01:49 +0000 (+0100)
Subject: ARM: 6521/1: perf: use raw_spinlock_t for pmu_lock
X-Git-Tag: v2.6.38-rc1~471^2^2~7
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=961ec6daa7b14f376c30d447a830fa4783a2112c;p=pandora-kernel.git

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

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>
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