From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Date: Wed, 28 Sep 2022 18:22:20 -0400

Subject: tracing: Wake up waiters when tracing is disabled

Git-commit: 2b0fd9a59b7990c161fa1cb7b79edb22847c87c2

Patch-mainline: v6.1-rc1

References: git-fixes

When tracing is disabled, there's no reason that waiters should stay

waiting, wake them up, otherwise tasks get stuck when they should be

flushing the buffers.

Cc: stable@vger.kernel.org

Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice")

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Acked-by: Petr Pavlu <petr.pavlu@suse.com>

---

 kernel/trace/trace.c | 6 ++++++

 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c

index 58afc83afc9d..bb5597c6bfc1 100644

--- a/kernel/trace/trace.c

+++ b/kernel/trace/trace.c

@@ -8334,6 +8334,10 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,

 		if (ret)

 			goto out;

+		/* No need to wait after waking up when tracing is off */

+		if (!tracer_tracing_is_on(iter->tr))

+			goto out;

+

 		/* Make sure we see the new wait_index */

 		smp_rmb();

 		if (wait_index != iter->wait_index)

@@ -9065,6 +9069,8 @@ rb_simple_write(struct file *filp, const char __user *ubuf,

 			tracer_tracing_off(tr);

 			if (tr->current_trace->stop)

 				tr->current_trace->stop(tr);

+			/* Wake up any waiters */

+			ring_buffer_wake_waiters(buffer, RING_BUFFER_ALL_CPUS);

 		}

 		mutex_unlock(&trace_types_lock);

 	}