[PATCH 04/13] perf: Simplify event_function*()

Peter Zijlstra
2023-11-02T15:33:06Z

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/events/core.c | 36 +++++++++++++++++++++---------------
1 file changed, 21 insertions(+), 15 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -214,6 +214,19 @@ struct event_function_struct {
void *data;
};

+typedef struct {
+ struct perf_cpu_context *cpuctx;
+ struct perf_event_context *ctx;
+} class_perf_ctx_lock_t;
+
+static inline void class_perf_ctx_lock_destructor(class_perf_ctx_lock_t *_T)
+{ perf_ctx_unlock(_T->cpuctx, _T->ctx); }
+
+static inline class_perf_ctx_lock_t
+class_perf_ctx_lock_constructor(struct perf_cpu_context *cpuctx,
+ struct perf_event_context *ctx)
+{ perf_ctx_lock(cpuctx, ctx); return (class_perf_ctx_lock_t){ cpuctx, ctx }; }
+
static int event_function(void *info)
{
struct event_function_struct *efs = info;
@@ -221,20 +234,17 @@ static int event_function(void *info)
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
struct perf_event_context *task_ctx = cpuctx->task_ctx;
- int ret = 0;

lockdep_assert_irqs_disabled();
+ guard(perf_ctx_lock)(cpuctx, task_ctx);

- perf_ctx_lock(cpuctx, task_ctx);
/*
* Since we do the IPI call without holding ctx->lock things can have
* changed, double check we hit the task we set out to hit.
*/
if (ctx->task) {
- if (ctx->task != current) {
- ret = -ESRCH;
- goto unlock;
- }
+ if (ctx->task != current)
+ return -ESRCH;

/*
* We only use event_function_call() on established contexts,
@@ -254,10 +264,8 @@ static int event_function(void *info)
}

efs->func(event, cpuctx, ctx, efs->data);
-unlock:
- perf_ctx_unlock(cpuctx, task_ctx);

- return ret;
+ return 0;
}

static void event_function_call(struct perf_event *event, event_f func, void *data)
@@ -329,11 +337,11 @@ static void event_function_local(struct
task_ctx = ctx;
}

- perf_ctx_lock(cpuctx, task_ctx);
+ guard(perf_ctx_lock)(cpuctx, task_ctx);

task = ctx->task;
if (task == TASK_TOMBSTONE)
- goto unlock;
+ return;

if (task) {
/*
@@ -343,18 +351,16 @@ static void event_function_local(struct
*/
if (ctx->is_active) {
if (WARN_ON_ONCE(task != current))
- goto unlock;
+ return;

if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))
- goto unlock;
+ return;
}
} else {
WARN_ON_ONCE(&cpuctx->ctx != ctx);
}

func(event, cpuctx, ctx, data);
-unlock:
- perf_ctx_unlock(cpuctx, task_ctx);
}

#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\