1 files changed, 31 insertions, 12 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c9c898307348..d390fea3a6a5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1955,15 +1955,36 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
+struct pipe_wait {
+	struct trace_iterator		*iter;
+	int				wait_index;
+};
+
+static bool wait_pipe_cond(void *data)
+{
+	struct pipe_wait *pwait = data;
+	struct trace_iterator *iter = pwait->iter;
+
+	if (atomic_read_acquire(&iter->wait_index) != pwait->wait_index)
+		return true;
+
+	return iter->closed;
+}
+
 static int wait_on_pipe(struct trace_iterator *iter, int full)
 {
+	struct pipe_wait pwait;
 	int ret;
 
 	/* Iterators are static, they should be filled or empty */
 	if (trace_buffer_iter(iter, iter->cpu_file))
 		return 0;
 
-	ret = ring_buffer_wait(iter->array_buffer->buffer, iter->cpu_file, full);
+	pwait.wait_index = atomic_read_acquire(&iter->wait_index);
+	pwait.iter = iter;
+
+	ret = ring_buffer_wait(iter->array_buffer->buffer, iter->cpu_file, full,
+			       wait_pipe_cond, &pwait);
 
 #ifdef CONFIG_TRACER_MAX_TRACE
 	/*
@@ -8398,9 +8419,9 @@ static int tracing_buffers_flush(struct file *file, fl_owner_t id)
 	struct ftrace_buffer_info *info = file->private_data;
 	struct trace_iterator *iter = &info->iter;
 
-	iter->wait_index++;
+	iter->closed = true;
 	/* Make sure the waiters see the new wait_index */
-	smp_wmb();
+	(void)atomic_fetch_inc_release(&iter->wait_index);
 
 	ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file);
 
@@ -8500,6 +8521,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		.spd_release	= buffer_spd_release,
 	};
 	struct buffer_ref *ref;
+	bool woken = false;
 	int page_size;
 	int entries, i;
 	ssize_t ret = 0;
@@ -8573,17 +8595,17 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 
 	/* did we read anything? */
 	if (!spd.nr_pages) {
-		long wait_index;
 
 		if (ret)
 			goto out;
 
+		if (woken)
+			goto out;
+
 		ret = -EAGAIN;
 		if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK))
 			goto out;
 
-		wait_index = READ_ONCE(iter->wait_index);
-
 		ret = wait_on_pipe(iter, iter->snapshot ? 0 : iter->tr->buffer_percent);
 		if (ret)
 			goto out;
@@ -8592,10 +8614,8 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		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)
-			goto out;
+		/* Iterate one more time to collect any new data then exit */
+		woken = true;
 
 		goto again;
 	}
@@ -8618,9 +8638,8 @@ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned
 
 	mutex_lock(&trace_types_lock);
 
-	iter->wait_index++;
 	/* Make sure the waiters see the new wait_index */
-	smp_wmb();
+	(void)atomic_fetch_inc_release(&iter->wait_index);
 
 	ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file);