On Fri, 02 May 2025 15:15:53 +0200 Paul Cacheux via B4 Relay <[email protected]> wrote:
> From: Paul Cacheux <[email protected]> > > The shared trace_probe_log variable can be accessed and modified > by multiple processes using tracefs at the same time, this new > mutex will guarantee it's always in a coherent state. Actually that's not happen. For the create part (and currently the event_log is used only in the creation), `dyn_event_ops_mutex` is already held in create_dyn_event(). Thus, it is already serialized. And even if there are multiple events are done in parallel, this is not enough because trace_probe_log::argc/argv can be changed before other user finishs to use the log. Thank you, > > There is no guarantee that multiple errors happening at the same > time will each have the correct error message, but at least this > won't crash. > > Fixes: ab105a4fb894 ("tracing: Use tracing error_log with probe events") > > Signed-off-by: Paul Cacheux <[email protected]> > --- > kernel/trace/trace_probe.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > index > 2eeecb6c95eea55502b83af6775b7b6f0cc5ab94..14a7a0b59cd20a8bc43e3e7c653e986081f924c8 > 100644 > --- a/kernel/trace/trace_probe.c > +++ b/kernel/trace/trace_probe.c > @@ -154,9 +154,11 @@ static const struct fetch_type *find_fetch_type(const > char *type, unsigned long > } > > static struct trace_probe_log trace_probe_log; > +static DEFINE_MUTEX(trace_probe_log_lock); > > void trace_probe_log_init(const char *subsystem, int argc, const char **argv) > { > + guard(mutex)(&trace_probe_log_lock); > trace_probe_log.subsystem = subsystem; > trace_probe_log.argc = argc; > trace_probe_log.argv = argv; > @@ -165,11 +167,13 @@ void trace_probe_log_init(const char *subsystem, int > argc, const char **argv) > > void trace_probe_log_clear(void) > { > + guard(mutex)(&trace_probe_log_lock); > memset(&trace_probe_log, 0, sizeof(trace_probe_log)); > } > > void trace_probe_log_set_index(int index) > { > + guard(mutex)(&trace_probe_log_lock); > trace_probe_log.index = index; > } > > @@ -178,6 +182,8 @@ void __trace_probe_log_err(int offset, int err_type) > char *command, *p; > int i, len = 0, pos = 0; > > + guard(mutex)(&trace_probe_log_lock); > + > if (!trace_probe_log.argv) > return; > > > -- > 2.49.0 > > -- Masami Hiramatsu (Google) <[email protected]>
