The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

2b0fd9a59b79 ("tracing: Wake up waiters when tracing is disabled") f3ddb74ad079 ("tracing: Wake up ring buffer waiters on closing of the file") efbbdaa22bb7 ("tracing: Show real address for trace event arguments") 8e99cf91b99b ("tracing: Do not allocate buffer in trace_find_next_entry() in atomic") ff895103a84a ("tracing: Save off entry when peeking at next entry") 03329f993978 ("tracing: Add tracefs file buffer_percentage") 2c2b0a78b373 ("ring-buffer: Add percentage of ring buffer full to wake up reader")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2b0fd9a59b7990c161fa1cb7b79edb22847c87c2 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" rostedt@goodmis.org Date: Wed, 28 Sep 2022 18:22:20 -0400 Subject: [PATCH] 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: e30f53aad2202 ("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 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); }