perf: Remove useless atomic_t

There's nothing atomic about atomic_set vs atomic_read; so remove the
atomic_t usage.

Also, make running_sample_length static as it really is (and should
be) local to this translation unit.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: eranian@google.com
Cc: Don Zickus <dzickus@redhat.com>
Cc: jmario@redhat.com
Cc: acme@infradead.org
Cc: dave.hansen@linux.intel.com
Link: http://lkml.kernel.org/n/tip-vw9lg588x1ic248whybjon0c@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5bd7fe43a7a22197379991a589fc4185c50a2e0c..028dad97760d74c68f639c091ff2a28031e6c0cd 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -175,8 +175,8 @@ int sysctl_perf_event_sample_rate __read_mostly     = DEFAULT_MAX_SAMPLE_RATE;
 static int max_samples_per_tick __read_mostly  = DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
 static int perf_sample_period_ns __read_mostly = DEFAULT_SAMPLE_PERIOD_NS;
 
-static atomic_t perf_sample_allowed_ns __read_mostly =
-       ATOMIC_INIT( DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100);
+static int perf_sample_allowed_ns __read_mostly =
+       DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;
 
 void update_perf_cpu_limits(void)
 {
@@ -184,7 +184,7 @@ void update_perf_cpu_limits(void)
 
        tmp *= sysctl_perf_cpu_time_max_percent;
        do_div(tmp, 100);
-       atomic_set(&perf_sample_allowed_ns, tmp);
+       ACCESS_ONCE(perf_sample_allowed_ns) = tmp;
 }
 
 static int perf_rotate_context(struct perf_cpu_context *cpuctx);
@@ -228,14 +228,15 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
  * we detect that events are taking too long.
  */
 #define NR_ACCUMULATED_SAMPLES 128
-DEFINE_PER_CPU(u64, running_sample_length);
+static DEFINE_PER_CPU(u64, running_sample_length);
 
 void perf_sample_event_took(u64 sample_len_ns)
 {
        u64 avg_local_sample_len;
        u64 local_samples_len;
+       u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);
 
-       if (atomic_read(&perf_sample_allowed_ns) == 0)
+       if (allowed_ns == 0)
                return;
 
        /* decay the counter by 1 average sample */
@@ -251,7 +252,7 @@ void perf_sample_event_took(u64 sample_len_ns)
         */
        avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;
 
-       if (avg_local_sample_len <= atomic_read(&perf_sample_allowed_ns))
+       if (avg_local_sample_len <= allowed_ns)
                return;
 
        if (max_samples_per_tick <= 1)
@@ -262,10 +263,9 @@ void perf_sample_event_took(u64 sample_len_ns)
        perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
 
        printk_ratelimited(KERN_WARNING
-                       "perf samples too long (%lld > %d), lowering "
+                       "perf samples too long (%lld > %lld), lowering "
                        "kernel.perf_event_max_sample_rate to %d\n",
-                       avg_local_sample_len,
-                       atomic_read(&perf_sample_allowed_ns),
+                       avg_local_sample_len, allowed_ns,
                        sysctl_perf_event_sample_rate);
 
        update_perf_cpu_limits();