struct task_struct *p = tfc->p;
if (p) {
- tfc->ret = -EAGAIN;
- if (task_cpu(p) != smp_processor_id() || !task_curr(p))
+ /* -EAGAIN */
+ if (task_cpu(p) != smp_processor_id())
+ return;
+
+ /*
+ * Now that we're on right CPU with IRQs disabled, we can test
+ * if we hit the right task without races.
+ */
+
+ tfc->ret = -ESRCH; /* No such (running) process */
+ if (p != current)
return;
}
.p = p,
.func = func,
.info = info,
- .ret = -ESRCH, /* No such (running) process */
+ .ret = -EAGAIN,
};
+ int ret;
- if (task_curr(p))
- smp_call_function_single(task_cpu(p), remote_function, &data, 1);
+ do {
+ ret = smp_call_function_single(task_cpu(p), remote_function, &data, 1);
+ if (!ret)
+ ret = data.ret;
+ } while (ret == -EAGAIN);
- return data.ret;
+ return ret;
}
/**
* rely on ctx->is_active and therefore cannot use event_function_call().
* See perf_install_in_context().
*
- * This is because we need a ctx->lock serialized variable (ctx->is_active)
- * to reliably determine if a particular task/context is scheduled in. The
- * task_curr() use in task_function_call() is racy in that a remote context
- * switch is not a single atomic operation.
- *
- * As is, the situation is 'safe' because we set rq->curr before we do the
- * actual context switch. This means that task_curr() will fail early, but
- * we'll continue spinning on ctx->is_active until we've passed
- * perf_event_task_sched_out().
- *
- * Without this ctx->lock serialized variable we could have race where we find
- * the task (and hence the context) would not be active while in fact they are.
- *
* If ctx->nr_events, then ctx->is_active and cpuctx->task_ctx are set.
*/
*/
if (ctx->task) {
if (ctx->task != current) {
- ret = -EAGAIN;
+ ret = -ESRCH;
goto unlock;
}
return;
}
-again:
if (task == TASK_TOMBSTONE)
return;
+again:
if (!task_function_call(task, event_function, &efs))
return;
* a concurrent perf_event_context_sched_out().
*/
task = ctx->task;
- if (task != TASK_TOMBSTONE) {
- if (ctx->is_active) {
- raw_spin_unlock_irq(&ctx->lock);
- goto again;
- }
- func(event, NULL, ctx, data);
+ if (task == TASK_TOMBSTONE) {
+ raw_spin_unlock_irq(&ctx->lock);
+ return;
}
+ if (ctx->is_active) {
+ raw_spin_unlock_irq(&ctx->lock);
+ goto again;
+ }
+ func(event, NULL, ctx, data);
raw_spin_unlock_irq(&ctx->lock);
}
event->tstamp_stopped = tstamp;
}
-static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
- struct perf_event_context *ctx);
+static void ctx_sched_out(struct perf_event_context *ctx,
+ struct perf_cpu_context *cpuctx,
+ enum event_type_t event_type);
static void
ctx_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
enum event_type_t event_type,
struct task_struct *task);
+static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
+ struct perf_event_context *ctx)
+{
+ if (!cpuctx->task_ctx)
+ return;
+
+ if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
+ return;
+
+ ctx_sched_out(ctx, cpuctx, EVENT_ALL);
+}
+
static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx,
struct task_struct *task)
/*
* Cross CPU call to install and enable a performance event
*
- * Must be called with ctx->mutex held
+ * Very similar to remote_function() + event_function() but cannot assume that
+ * things like ctx->is_active and cpuctx->task_ctx are set.
*/
static int __perf_install_in_context(void *info)
{
- struct perf_event_context *ctx = info;
+ struct perf_event *event = info;
+ struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
struct perf_event_context *task_ctx = cpuctx->task_ctx;
+ bool activate = true;
+ int ret = 0;
raw_spin_lock(&cpuctx->ctx.lock);
if (ctx->task) {
raw_spin_lock(&ctx->lock);
- /*
- * If we hit the 'wrong' task, we've since scheduled and
- * everything should be sorted, nothing to do!
- */
task_ctx = ctx;
- if (ctx->task != current)
+
+ /* If we're on the wrong CPU, try again */
+ if (task_cpu(ctx->task) != smp_processor_id()) {
+ ret = -ESRCH;
goto unlock;
+ }
/*
- * If task_ctx is set, it had better be to us.
+ * If we're on the right CPU, see if the task we target is
+ * current, if not we don't have to activate the ctx, a future
+ * context switch will do that for us.
*/
- WARN_ON_ONCE(cpuctx->task_ctx != ctx && cpuctx->task_ctx);
+ if (ctx->task != current)
+ activate = false;
+ else
+ WARN_ON_ONCE(cpuctx->task_ctx && cpuctx->task_ctx != ctx);
+
} else if (task_ctx) {
raw_spin_lock(&task_ctx->lock);
}
- ctx_resched(cpuctx, task_ctx);
+ if (activate) {
+ ctx_sched_out(ctx, cpuctx, EVENT_TIME);
+ add_event_to_ctx(event, ctx);
+ ctx_resched(cpuctx, task_ctx);
+ } else {
+ add_event_to_ctx(event, ctx);
+ }
+
unlock:
perf_ctx_unlock(cpuctx, task_ctx);
- return 0;
+ return ret;
}
/*
- * Attach a performance event to a context
+ * Attach a performance event to a context.
+ *
+ * Very similar to event_function_call, see comment there.
*/
static void
perf_install_in_context(struct perf_event_context *ctx,
struct perf_event *event,
int cpu)
{
- struct task_struct *task = NULL;
+ struct task_struct *task = READ_ONCE(ctx->task);
lockdep_assert_held(&ctx->mutex);
if (event->cpu != -1)
event->cpu = cpu;
+ if (!task) {
+ cpu_function_call(cpu, __perf_install_in_context, event);
+ return;
+ }
+
+ /*
+ * Should not happen, we validate the ctx is still alive before calling.
+ */
+ if (WARN_ON_ONCE(task == TASK_TOMBSTONE))
+ return;
+
/*
* Installing events is tricky because we cannot rely on ctx->is_active
* to be set in case this is the nr_events 0 -> 1 transition.
- *
- * So what we do is we add the event to the list here, which will allow
- * a future context switch to DTRT and then send a racy IPI. If the IPI
- * fails to hit the right task, this means a context switch must have
- * happened and that will have taken care of business.
*/
- raw_spin_lock_irq(&ctx->lock);
- task = ctx->task;
-
+again:
/*
- * If between ctx = find_get_context() and mutex_lock(&ctx->mutex) the
- * ctx gets destroyed, we must not install an event into it.
- *
- * This is normally tested for after we acquire the mutex, so this is
- * a sanity check.
+ * Cannot use task_function_call() because we need to run on the task's
+ * CPU regardless of whether its current or not.
*/
+ if (!cpu_function_call(task_cpu(task), __perf_install_in_context, event))
+ return;
+
+ raw_spin_lock_irq(&ctx->lock);
+ task = ctx->task;
if (WARN_ON_ONCE(task == TASK_TOMBSTONE)) {
+ /*
+ * Cannot happen because we already checked above (which also
+ * cannot happen), and we hold ctx->mutex, which serializes us
+ * against perf_event_exit_task_context().
+ */
raw_spin_unlock_irq(&ctx->lock);
return;
}
-
- if (ctx->is_active) {
- update_context_time(ctx);
- update_cgrp_time_from_event(event);
- }
-
- add_event_to_ctx(event, ctx);
raw_spin_unlock_irq(&ctx->lock);
-
- if (task)
- task_function_call(task, __perf_install_in_context, ctx);
- else
- cpu_function_call(cpu, __perf_install_in_context, ctx);
+ /*
+ * Since !ctx->is_active doesn't mean anything, we must IPI
+ * unconditionally.
+ */
+ goto again;
}
/*
event->state <= PERF_EVENT_STATE_ERROR)
return;
- update_context_time(ctx);
+ if (ctx->is_active)
+ ctx_sched_out(ctx, cpuctx, EVENT_TIME);
+
__perf_event_mark_enabled(event);
if (!ctx->is_active)
return;
if (!event_filter_match(event)) {
- if (is_cgroup_event(event)) {
- perf_cgroup_set_timestamp(current, ctx); // XXX ?
+ if (is_cgroup_event(event))
perf_cgroup_defer_enabled(event);
- }
+ ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
return;
}
* If the event is in a group and isn't the group leader,
* then don't put it on unless the group is on.
*/
- if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
+ if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) {
+ ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
return;
+ }
task_ctx = cpuctx->task_ctx;
if (ctx->task)
perf_cgroup_sched_out(task, next);
}
-static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
- struct perf_event_context *ctx)
-{
- if (!cpuctx->task_ctx)
- return;
-
- if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
- return;
-
- ctx_sched_out(ctx, cpuctx, EVENT_ALL);
-}
-
/*
* Called with IRQs disabled
*/
projects / linux-2.6-block.git / blobdiff