[PATCH v2 0/2] tracing: Fix deadlock in hwlat tracer

Wei Li
2024-11-21T02:05:44Z

This patchset fixes a deadlock issue found in concurrent CPU-hotplug and
tracer-toggling testing:

Background: *test_hotplug.sh*
```
#!/bin/sh

while true
do
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
done
```

Test: *test_hwlat.sh*
```
#!/bin/sh

echo per-cpu > /sys/kernel/debug/tracing/hwlat_detector/mode
while true
do
echo hwlat > /sys/kernel/debug/tracing/current_tracer
echo nop > /sys/kernel/debug/tracing/current_tracer
done
```

v1 -> v2:
- The previous solution try to make the mutex obtaining in kthread_fn()
interruptible to fix this issue. To make the logic clearer, change to
remove the mutex_lock in this version.

Links:
v1: https://lore.kernel.org/linux-trace-kernel/20240924094515.3561410-6-liwei391@huawei.com/

Wei Li (2):
tracing: Allow custom read/write processing in
trace_min_max_{write,read}()
tracing/hwlat: Fix deadlock in cpuhp processing

kernel/trace/trace.c | 13 ++++++++++---
kernel/trace/trace.h | 2 ++
kernel/trace/trace_hwlat.c | 15 +++++++++++----
3 files changed, 23 insertions(+), 7 deletions(-)

--
2.25.1