perf_counter: Rework the perf counter disable/enable
The current disable/enable mechanism is:
token = hw_perf_save_disable();
...
/* do bits */
...
hw_perf_restore(token);
This works well, provided that the use nests properly. Except we don't.
x86 NMI/INT throttling has non-nested use of this, breaking things. Therefore
provide a reference counter disable/enable interface, where the first disable
disables the hardware, and the last enable enables the hardware again.
[ Impact: refactor, simplify the PMU disable/enable logic ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c
index 15cdc8e..bb1b463 100644
--- a/arch/powerpc/kernel/perf_counter.c
+++ b/arch/powerpc/kernel/perf_counter.c
@@ -386,7 +386,7 @@
* Disable all counters to prevent PMU interrupts and to allow
* counters to be added or removed.
*/
-u64 hw_perf_save_disable(void)
+void hw_perf_disable(void)
{
struct cpu_hw_counters *cpuhw;
unsigned long ret;
@@ -428,7 +428,6 @@
mb();
}
local_irq_restore(flags);
- return ret;
}
/*
@@ -436,7 +435,7 @@
* If we were previously disabled and counters were added, then
* put the new config on the PMU.
*/
-void hw_perf_restore(u64 disable)
+void hw_perf_enable(void)
{
struct perf_counter *counter;
struct cpu_hw_counters *cpuhw;
@@ -448,9 +447,12 @@
int n_lim;
int idx;
- if (disable)
- return;
local_irq_save(flags);
+ if (!cpuhw->disabled) {
+ local_irq_restore(flags);
+ return;
+ }
+
cpuhw = &__get_cpu_var(cpu_hw_counters);
cpuhw->disabled = 0;
@@ -649,19 +651,18 @@
/*
* Add a counter to the PMU.
* If all counters are not already frozen, then we disable and
- * re-enable the PMU in order to get hw_perf_restore to do the
+ * re-enable the PMU in order to get hw_perf_enable to do the
* actual work of reconfiguring the PMU.
*/
static int power_pmu_enable(struct perf_counter *counter)
{
struct cpu_hw_counters *cpuhw;
unsigned long flags;
- u64 pmudis;
int n0;
int ret = -EAGAIN;
local_irq_save(flags);
- pmudis = hw_perf_save_disable();
+ perf_disable();
/*
* Add the counter to the list (if there is room)
@@ -685,7 +686,7 @@
ret = 0;
out:
- hw_perf_restore(pmudis);
+ perf_enable();
local_irq_restore(flags);
return ret;
}
@@ -697,11 +698,10 @@
{
struct cpu_hw_counters *cpuhw;
long i;
- u64 pmudis;
unsigned long flags;
local_irq_save(flags);
- pmudis = hw_perf_save_disable();
+ perf_disable();
power_pmu_read(counter);
@@ -735,7 +735,7 @@
cpuhw->mmcr[0] &= ~(MMCR0_PMXE | MMCR0_FCECE);
}
- hw_perf_restore(pmudis);
+ perf_enable();
local_irq_restore(flags);
}