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[PATCH v2 2/5] MIPS/Perf-events: Remove erroneous check on active_events

To: <ralf@linux-mips.org>, <linux-mips@linux-mips.org>
Subject: [PATCH v2 2/5] MIPS/Perf-events: Remove erroneous check on active_events
From: Deng-Cheng Zhu <dczhu@mips.com>
Date: Tue, 22 Nov 2011 11:28:46 +0800
Cc: <eyal@mips.com>, <zenon@mips.com>, Deng-Cheng Zhu <dczhu@mips.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>, Arnaldo Carvalho de Melo <acme@ghostprotocols.net>, David Daney <david.daney@cavium.com>
In-reply-to: <1321932528-21098-1-git-send-email-dczhu@mips.com>
References: <1321932528-21098-1-git-send-email-dczhu@mips.com>
Sender: linux-mips-bounce@linux-mips.org
Port the following patch for ARM by Mark Rutland:

- 57ce9bb39b476accf8fba6e16aea67ed76ea523d
    ARM: 6902/1: perf: Remove erroneous check on active_events

    When initialising a PMU, there is a check to protect against races with
    other CPUs filling all of the available event slots. Since armpmu_add
    checks that an event can be scheduled, we do not need to do this at
    initialisation time. Furthermore the current code is broken because it
    assumes that atomic_inc_not_zero will unconditionally increment
    active_counts and then tries to decrement it again on failure.

    This patch removes the broken, redundant code.

Signed-off-by: Deng-Cheng Zhu <dczhu@mips.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: David Daney <david.daney@cavium.com>
---
 arch/mips/kernel/perf_event_mipsxx.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/arch/mips/kernel/perf_event_mipsxx.c 
b/arch/mips/kernel/perf_event_mipsxx.c
index ab4c761..b5d6b3f 100644
--- a/arch/mips/kernel/perf_event_mipsxx.c
+++ b/arch/mips/kernel/perf_event_mipsxx.c
@@ -621,11 +621,6 @@ static int mipspmu_event_init(struct perf_event *event)
                return -ENODEV;
 
        if (!atomic_inc_not_zero(&active_events)) {
-               if (atomic_read(&active_events) > MIPS_MAX_HWEVENTS) {
-                       atomic_dec(&active_events);
-                       return -ENOSPC;
-               }
-
                mutex_lock(&pmu_reserve_mutex);
                if (atomic_read(&active_events) == 0)
                        err = mipspmu_get_irq();
-- 
1.7.1


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