tracing: Wake up waiters when tracing is disabled

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: e3d3ed5fb5a15 ("tracing: Do not busy wait in buffer splice")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 58afc83afc9d5a1ba412d8f78d2e3f2d4066e068..bb5597c6bfc122b97256323ed4dc5cc1bdb565b7 100644 (file)
--- 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);
        }