Commit 0878355b authored Jan 09, 2022 by Nikita Yushchenko Committed by Steven Rostedt Jan 13, 2022

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

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: bce29ac9 ("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>

parent 6e1b4bd1

kernel/trace/trace_osnoise.c

+16 −4

Original line number	Diff line number	Diff line
		@@ -2122,6 +2122,13 @@ 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
		*/
		@@ -2154,7 +2161,14 @@ static int osnoise_workload_start(void)

		retval = start_per_cpu_kthreads();
		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;
		}

		@@ -2185,9 +2199,7 @@ 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)