samples/trace_printk: Wait for IRQ work to finish

commit 01f36a554e3ef32f9fc4b81a4437cf08fd0e4742 upstream.

trace_printk schedules work via irq_work_queue(), but doesn't
wait until it was processed. The kprobe_module.tc testcase does:

:;: "Load module again, which means the event1 should be recorded";:
modprobe trace-printk
grep "event1:" trace

so the grep which checks the trace file might run before the irq work
was processed. Fix this by adding a irq_work_sync().

Link: http://lore.kernel.org/linux-trace-devel/20191218074427.96184-3-svens@linux.ibm.com
Cc: stable@vger.kernel.org
Fixes: af2a0750f3749 ("selftests/ftrace: Improve kprobe on module testcase to load/unload module")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/samples/trace_printk/trace-printk.c b/samples/trace_printk/trace-printk.c
index 7affc3b..cfc1595 100644 (file)
--- a/samples/trace_printk/trace-printk.c
+++ b/samples/trace_printk/trace-printk.c
@@ -36,6 +36,7 @@ static int __init trace_printk_init(void)
 
        /* Kick off printing in irq context */
        irq_work_queue(&irqwork);
+       irq_work_sync(&irqwork);
 
        trace_printk("This is a %s that will use trace_bprintk()\n",
                     "static string");