On 2023/9/7 05:37, Steven Rostedt wrote:

On Wed, 6 Sep 2023 10:37:18 -0400
Steven Rostedt [off-list ref] wrote:

quoted

quoted

Log details,
-------------
# ok 45 ftrace - test tracing error log support
<47>[ 1373.662292] systemd-journald[90]: Sent WATCHDOG=1 notification.
# ok 46 Test creation and deletion of trace instances while setting an event

It's definitely a race with the creation and deletion of instances.

I'm going to run it on my laptop VM and see if that reproduces it. My other
VM is on a pretty powerful machine, and perhaps that's keeping it from
hitting the race.

Putting in a while loop of:

   # while :; do ./ftracetest test.d/instances/instance-event.tc ; done

In test.d/instances/instance-event.tc, concurrently create/delete/access
intances just about 1 second and then killed them, it may cause missing
the race.

No longer sleep and kill, following testcase can also reproduce:

#!/bin/bash

cd /sys/kernel/tracing/instances

instance_slam() {
   while :; do
           mkdir foo 2> /dev/null
           rmdir foo 2> /dev/null
   done
}

instance_set() {
         while :; do
                 echo 1 > foo/events/sched/sched_switch/enable
         done 2> /dev/null
}

instance_slam &
p1=$!
echo $p1

instance_set &
p2=$!
echo $p2

--

Thanks,
Zheng Yejian

eventually triggered the bug. Looks like this is really an existing bug not
related to the eventfs, but the eventfs code actually opened up the window
of this race.

Hopefully I'll have a fix shortly.

-- Steve