From: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx> commit 0878355b51f5f26632e652c848a8e174bb02d22d 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@xxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Fixes: bce29ac9ce0b ("trace: Add osnoise tracer") Acked-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> Signed-off-by: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/trace/trace_osnoise.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -1932,6 +1932,13 @@ out_unhook_irq: 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 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 t stop_per_cpu_kthreads(); - unhook_irq_events(); - unhook_softirq_events(); - unhook_thread_events(); + osnoise_unhook_events(); osnoise_busy = false; }
