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: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 139e3c8..d53c0ab 100644 (file)
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -560,11 +560,6 @@ static int armpmu_event_init(struct perf_event *event)
        event->destroy = hw_perf_event_destroy;
 
        if (!atomic_inc_not_zero(&active_events)) {
-               if (atomic_read(&active_events) > armpmu->num_events) {
-                       atomic_dec(&active_events);
-                       return -ENOSPC;
-               }
-
                mutex_lock(&pmu_reserve_mutex);
                if (atomic_read(&active_events) == 0) {
                        err = armpmu_reserve_hardware();