linux-kernel - Re: [PATCH] perf, core: Fix initial task

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Date:	Tue, 07 Jun 2011 00:23:28 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	paulus@...ba.org, mingo@...e.hu, linux-kernel@...r.kernel.org,
	oleg@...hat.com
Subject: Re: [PATCH] perf, core: Fix initial task_ctx/event installation

This works for me..

---
 kernel/events/core.c |   28 +++++++++++++++++-----------
 1 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index ba89f40..5e8c7b1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1505,25 +1505,31 @@ static int  __perf_install_in_context(void *info)
 	struct perf_event_context *task_ctx = cpuctx->task_ctx;
 	struct task_struct *task = current;
 
-	perf_ctx_lock(cpuctx, cpuctx->task_ctx);
+	perf_ctx_lock(cpuctx, task_ctx);
 	perf_pmu_disable(cpuctx->ctx.pmu);
 
 	/*
 	 * If there was an active task_ctx schedule it out.
 	 */
-	if (task_ctx) {
+	if (task_ctx)
 		task_ctx_sched_out(task_ctx);
-		/*
-		 * If the context we're installing events in is not the
-		 * active task_ctx, flip them.
-		 */
-		if (ctx->task && task_ctx != ctx) {
-			raw_spin_unlock(&cpuctx->ctx.lock);
-			raw_spin_lock(&ctx->lock);
-			cpuctx->task_ctx = task_ctx = ctx;
-		}
+
+	/*
+	 * If the context we're installing events in is not the
+	 * active task_ctx, flip them.
+	 */
+	if (ctx->task && task_ctx != ctx) {
+		if (task_ctx)
+			raw_spin_unlock(&task_ctx->lock);
+		raw_spin_lock(&ctx->lock);
+		task_ctx = ctx;
+	}
+
+	if (task_ctx) {
+		cpuctx->task_ctx = task_ctx;
 		task = task_ctx->task;
 	}
+
 	cpu_ctx_sched_out(cpuctx, EVENT_ALL);
 
 	update_context_time(ctx);


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