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Subject[RFC][PATCH 07/12] perf: Simplify/fix perf_event_enable() event scheduling
Like enable_on_exec, perf_event_enable() event scheduling has problems
respecting the context hierarchy when trying to schedule events (for
example, it will try and add a pinned event without first removing
existing flexible events).

So simplify it by using the new ctx_resched() call which will DTRT.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/events/core.c | 31 +++++--------------------------
1 file changed, 5 insertions(+), 26 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2188,7 +2188,7 @@ static int __perf_event_enable(void *inf
struct perf_event_context *ctx = event->ctx;
struct perf_event *leader = event->group_leader;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
- int err;
+ struct perf_event_context *task_ctx = cpuctx->task_ctx;

/*
* There's a time window between 'ctx->is_active' check
@@ -2202,7 +2202,8 @@ static int __perf_event_enable(void *inf
if (!ctx->is_active)
return -EINVAL;

- raw_spin_lock(&ctx->lock);
+ perf_ctx_lock(cpuctx, task_ctx);
+ WARN_ON_ONCE(&cpuctx->ctx != ctx && task_ctx != ctx);
update_context_time(ctx);

if (event->state >= PERF_EVENT_STATE_INACTIVE)
@@ -2228,32 +2229,10 @@ static int __perf_event_enable(void *inf
if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
goto unlock;

- if (!group_can_go_on(event, cpuctx, 1)) {
- err = -EEXIST;
- } else {
- if (event == leader)
- err = group_sched_in(event, cpuctx, ctx);
- else
- err = event_sched_in(event, cpuctx, ctx);
- }
-
- if (err) {
- /*
- * If this event can't go on and it's part of a
- * group, then the whole group has to come off.
- */
- if (leader != event) {
- group_sched_out(leader, cpuctx, ctx);
- perf_mux_hrtimer_restart(cpuctx);
- }
- if (leader->attr.pinned) {
- update_group_times(leader);
- leader->state = PERF_EVENT_STATE_ERROR;
- }
- }
+ ctx_resched(cpuctx, task_ctx);

unlock:
- raw_spin_unlock(&ctx->lock);
+ perf_ctx_unlock(cpuctx, task_ctx);

return 0;
}

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