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tracing/osnoise: Properly unhook events if start_per_cpu_kthreads() fails

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commit 0878355b51 upstream.

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 normal tracer disable.

Link: https://lkml.kernel.org/r/20220109153459.3701773-1-nikita.yushchenko@virtuozzo.com

Cc: stable@vger.kernel.org
Fixes: bce29ac9ce ("trace: Add osnoise tracer")
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Nikita Yushchenko <nikita.yushchenko@virtuozzo.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nikita Yushchenko 2022-01-09 18:34:59 +03:00 committed by Greg Kroah-Hartman
parent 0d99b0a7c3
commit cb77c81d34
1 changed files with 16 additions and 4 deletions
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20
kernel/trace/trace_osnoise.c
View file

@ -1932,6 +1932,13 @@ static int osnoise_hook_events(void)
return -EINVAL;
}
static void osnoise_unhook_events(void)
{
unhook_thread_events();
unhook_softirq_events();
unhook_irq_events();
}
static int __osnoise_tracer_start(struct trace_array *tr)
{
int retval;
@ -1949,7 +1956,14 @@ static int __osnoise_tracer_start(struct trace_array *tr)
retval = start_per_cpu_kthreads(tr);
if (retval) {
unhook_irq_events();
trace_osnoise_callback_enabled = false;
/*
* Make sure that ftrace_nmi_enter/exit() see
* trace_osnoise_callback_enabled as false before continuing.
*/
barrier();
osnoise_unhook_events();
return retval;
}
@ -1981,9 +1995,7 @@ static void osnoise_tracer_stop(struct trace_array *tr)
stop_per_cpu_kthreads();
unhook_irq_events();
unhook_softirq_events();
unhook_thread_events();
osnoise_unhook_events();
osnoise_busy = false;
}