tracing: Fix trace_pipe behavior for instance traces
authorTahsin Erdogan <tahsin@google.com>
Sun, 17 Sep 2017 10:23:48 +0000 (03:23 -0700)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Tue, 19 Sep 2017 22:33:42 +0000 (18:33 -0400)
commit75df6e688ccd517e339a7c422ef7ad73045b18a2
tree01bec25348768812dceb33f95d41b1bb09c1094d
parentc7b3ae0bd2ca658c7a71c49901d08c590294fac9
tracing: Fix trace_pipe behavior for instance traces

When reading data from trace_pipe, tracing_wait_pipe() performs a
check to see if tracing has been turned off after some data was read.
Currently, this check always looks at global trace state, but it
should be checking the trace instance where trace_pipe is located at.

Because of this bug, cat instances/i1/trace_pipe in the following
script will immediately exit instead of waiting for data:

cd /sys/kernel/debug/tracing
echo 0 > tracing_on
mkdir -p instances/i1
echo 1 > instances/i1/tracing_on
echo 1 > instances/i1/events/sched/sched_process_exec/enable
cat instances/i1/trace_pipe

Link: http://lkml.kernel.org/r/20170917102348.1615-1-tahsin@google.com
Cc: stable@vger.kernel.org
Fixes: 10246fa35d4f ("tracing: give easy way to clear trace buffer")
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
kernel/trace/trace.c