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Subject[PATCH vz9] trace/osnoise: fix event unhooking
Date
If start_per_cpu_kthreads() called from osnoise_workload_start() returns
error, event hooks are left in broken state: unhook_irq_events() called
but unhook_thread_events() and unhook_softirq_events() not called, and
trace_osnoise_callback_enabled flag not cleared.

On the next tracer enable, hooks get not installed due to
trace_osnoise_callback_enabled flag.

And on the further tracer disable an attempt to remove non-installed
hooks happened, hitting a WARN_ON_ONCE() in tracepoint_remove_func().

Fix the error path by adding the missing part of cleanup.
While at this, introduce osnoise_unhook_events() to avoid code
duplication between this error path and notmal tracer disable.

Fixes: bce29ac9ce0b ("trace: Add osnoise tracer")
Signed-off-by: Nikita Yushchenko <nikita.yushchenko@virtuozzo.com>
---
kernel/trace/trace_osnoise.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 7520d43aed55..aa6f26612ccc 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2123,6 +2123,13 @@ static int osnoise_hook_events(void)
return -EINVAL;
}

+static void osnoise_unhook_events(void)
+{
+ unhook_thread_events();
+ unhook_softirq_events();
+ unhook_irq_events();
+}
+
/*
* osnoise_workload_start - start the workload and hook to events
*/
@@ -2155,7 +2162,8 @@ static int osnoise_workload_start(void)

retval = start_per_cpu_kthreads();
if (retval) {
- unhook_irq_events();
+ trace_osnoise_callback_enabled = false;
+ osnoise_unhook_events();
return retval;
}

@@ -2186,9 +2194,7 @@ static void osnoise_workload_stop(void)

stop_per_cpu_kthreads();

- unhook_irq_events();
- unhook_softirq_events();
- unhook_thread_events();
+ osnoise_unhook_events();
}

static void osnoise_tracer_start(struct trace_array *tr)
--
2.30.2
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