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Date: Tue, 27 Jan 2015 20:03:47 +0200
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
Robert Richter <rric@...nel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Mike Galbraith <efault@....de>,
Paul Mackerras <paulus@...ba.org>,
Stephane Eranian <eranian@...gle.com>,
Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
adrian.hunter@...el.com, markus.t.metzger@...el.com,
mathieu.poirier@...aro.org, Kaixu Xia <kaixu.xia@...aro.org>,
acme@...radead.org
Subject: Re: [PATCH v9 12/14] x86: perf: intel_pt: Intel PT PMU driver
Peter Zijlstra <peterz@...radead.org> writes:
>
> Yes that'll work.
Ok, let me respin this last patch, with the per-task event counter to
prevent cpu-wide events together with per-task events. The idea is that
cpu-wide events are disallowed when per-task events exist on this pmu
and vice versa. It adds an atomic counter to struct pmu to account for
per-task events.
If this looks all right to you, I can resend the patchset.
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
include/linux/perf_event.h | 1 +
kernel/events/core.c | 87 ++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 81 insertions(+), 7 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index e00d59dc08..bdbba674de 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -189,6 +189,7 @@ struct pmu {
int * __percpu pmu_disable_count;
struct perf_cpu_context * __percpu pmu_cpu_context;
+ atomic_t nr_per_task_events;
int task_ctx_nr;
int hrtimer_interval_ms;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 35ed22a0d8..c0a0cd90ba 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3335,6 +3335,44 @@ static void unaccount_event(struct perf_event *event)
unaccount_event_cpu(event, event->cpu);
}
+static int account_per_task_counter(struct perf_event *event)
+{
+ struct pmu *pmu = event->pmu;
+
+ if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
+ return 0;
+
+ /*
+ * Prevent co-existence of per-task and cpu-wide events on the
+ * same exclusive pmu.
+ *
+ * Negative pmu::nr_per_task_events means there are cpu-wide
+ * events on this "exclusive" pmu, positive means there are
+ * per-task events.
+ */
+ if (event->cpu == -1 &&
+ !atomic_inc_unless_negative(&pmu->nr_per_task_events))
+ return -EBUSY;
+ else if (!(event->attach_state & PERF_ATTACH_TASK) &&
+ !atomic_dec_unless_positive(&pmu->nr_per_task_events))
+ return -EBUSY;
+
+ return 0;
+}
+
+static void unaccount_per_task_counter(struct perf_event *event)
+{
+ struct pmu *pmu = event->pmu;
+
+ if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
+ return 0;
+
+ if (event->cpu == -1)
+ atomic_dec(&pmu->nr_per_task_events);
+ else if (!(event->attach_state & PERF_ATTACH_TASK))
+ atomic_inc(&pmu->nr_per_task_events);
+}
+
static void __free_event(struct perf_event *event)
{
if (!event->parent) {
@@ -3348,8 +3386,11 @@ static void __free_event(struct perf_event *event)
if (event->ctx)
put_ctx(event->ctx);
- if (event->pmu)
+ if (event->pmu) {
+ unaccount_per_task_counter(event);
+
module_put(event->pmu->module);
+ }
call_rcu(&event->rcu_head, free_event_rcu);
}
@@ -6908,6 +6949,7 @@ got_cpu_context:
pmu->event_idx = perf_event_idx_default;
list_add_rcu(&pmu->entry, &pmus);
+ atomic_set(&pmu->nr_per_task_events, 0);
ret = 0;
unlock:
mutex_unlock(&pmus_lock);
@@ -7143,16 +7185,23 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
goto err_ns;
}
+ err = account_per_task_counter(event);
+ if (err)
+ goto err_pmu;
+
if (!event->parent) {
if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
err = get_callchain_buffers();
if (err)
- goto err_pmu;
+ goto err_per_task;
}
}
return event;
+err_per_task:
+ unaccount_per_task_counter(event);
+
err_pmu:
if (event->destroy)
event->destroy(event);
@@ -7360,14 +7409,11 @@ static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2)
return false;
}
-static bool exclusive_event_ok(struct perf_event *event,
- struct perf_event_context *ctx)
+static bool __exclusive_event_ok(struct perf_event *event,
+ struct perf_event_context *ctx)
{
struct perf_event *iter_event;
- if (!(event->pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
- return true;
-
list_for_each_entry(iter_event, &ctx->event_list, event_entry) {
if (exclusive_event_match(iter_event, event))
return false;
@@ -7376,6 +7422,33 @@ static bool exclusive_event_ok(struct perf_event *event,
return true;
}
+static bool exclusive_event_ok(struct perf_event *event,
+ struct perf_event_context *ctx)
+{
+ struct pmu *pmu = event->pmu;
+ bool ret = true;
+
+ if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
+ return true;
+
+ if (!__exclusive_event_ok(event, ctx))
+ return false;
+
+ if (ctx->task) {
+ if (event->cpu != -1) {
+ struct perf_event_context *cpuctx;
+
+ cpuctx = &per_cpu_ptr(pmu->pmu_cpu_context, event->cpu)->ctx;
+
+ mutex_lock(&cpuctx->mutex);
+ ret = __exclusive_event_ok(event, cpuctx);
+ mutex_unlock(&cpuctx->mutex);
+ }
+ }
+
+ return ret;
+}
+
/**
* sys_perf_event_open - open a performance event, associate it to a task/cpu
*
--
2.1.4
--
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