On Sat, 10 May 2025 07:44:56 +0900 Masami Hiramatsu (Google) <[email protected]> wrote:
> 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. Oops, if user writes some commands not directly from dynevent, (e.g. tracefs/{kprobe_events,uprobe_events} )the mutex is not held. Hmm, we need to make another patch. > > 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. But this is still valid. We need to reroute the creation to dynamic_events. Thank you, > > 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]> -- Masami Hiramatsu (Google) <[email protected]>
