linux-kernel - [PATCH v3 26/57] perf: Simplify event

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Message-ID: <20230612093539.371360635@infradead.org>
Date:   Mon, 12 Jun 2023 11:07:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     torvalds@...ux-foundation.org, keescook@...omium.org,
        gregkh@...uxfoundation.org, pbonzini@...hat.com
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Subject: [PATCH v3 26/57] perf: Simplify event_function*()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c |   39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -214,6 +214,25 @@ 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)
+{
+	if (_T->cpuctx)
+		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;
@@ -224,17 +243,15 @@ static int event_function(void *info)
 	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,
@@ -254,8 +271,6 @@ static int event_function(void *info)
 	}
 
 	efs->func(event, cpuctx, ctx, efs->data);
-unlock:
-	perf_ctx_unlock(cpuctx, task_ctx);
 
 	return ret;
 }
@@ -329,11 +344,11 @@ 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 +358,16 @@ 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 |\