MIPS/Perf-events: Remove erroneous check on active_events

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>
Cc: Eyal Barzilay <eyal@mips.com>
Cc: Zenon Fortuna <zenon@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/3106/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/perf_event_mipsxx.c b/arch/mips/kernel/perf_event_mipsxx.c
index ab4c761..b5d6b3f 100644 (file)
--- 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();