linux-kernel - [tip: perf/core] perf: Really fix event_function

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Message-ID: <172361423558.2215.17332323799213170213.tip-bot2@tip-bot2>
Date: Wed, 14 Aug 2024 05:43:55 -0000
From: "tip-bot2 for Namhyung Kim" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Pengfei Xu <pengfei.xu@...el.com>,
 Naresh Kamboju <naresh.kamboju@...aro.org>,
 Namhyung Kim <namhyung@...nel.org>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf: Really fix event_function_call() locking

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     fe826cc2654e8561b64246325e6a51b62bf2488c
Gitweb:        https://git.kernel.org/tip/fe826cc2654e8561b64246325e6a51b62bf2488c
Author:        Namhyung Kim <namhyung@...nel.org>
AuthorDate:    Tue, 13 Aug 2024 22:55:11 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 14 Aug 2024 07:39:09 +02:00

perf: Really fix event_function_call() locking

Commit 558abc7e3f89 ("perf: Fix event_function_call() locking") lost
IRQ disabling by mistake.

Fixes: 558abc7e3f89 ("perf: Fix event_function_call() locking")
Reported-by: Pengfei Xu <pengfei.xu@...el.com>
Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Tested-by: Pengfei Xu <pengfei.xu@...el.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9893ba5..c6a720f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -298,8 +298,8 @@ unlock:
 static void event_function_call(struct perf_event *event, event_f func, void *data)
 {
 	struct perf_event_context *ctx = event->ctx;
-	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
 	struct task_struct *task = READ_ONCE(ctx->task); /* verified in event_function */
+	struct perf_cpu_context *cpuctx;
 	struct event_function_struct efs = {
 		.event = event,
 		.func = func,
@@ -327,22 +327,25 @@ again:
 	if (!task_function_call(task, event_function, &efs))
 		return;
 
+	local_irq_disable();
+	cpuctx = this_cpu_ptr(&perf_cpu_context);
 	perf_ctx_lock(cpuctx, ctx);
 	/*
 	 * Reload the task pointer, it might have been changed by
 	 * a concurrent perf_event_context_sched_out().
 	 */
 	task = ctx->task;
-	if (task == TASK_TOMBSTONE) {
-		perf_ctx_unlock(cpuctx, ctx);
-		return;
-	}
+	if (task == TASK_TOMBSTONE)
+		goto unlock;
 	if (ctx->is_active) {
 		perf_ctx_unlock(cpuctx, ctx);
+		local_irq_enable();
 		goto again;
 	}
 	func(event, NULL, ctx, data);
+unlock:
 	perf_ctx_unlock(cpuctx, ctx);
+	local_irq_enable();
 }
 
 /*