From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8924925F7BF; Fri, 9 May 2025 23:57:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746835071; cv=none; b=uAInjmZfO4ANJBsTF62I4FGuU2WNbJmbwKYkqgmWXn3Hkn4kypdZK9wutAjP0Gpum4+IiWe7srfJCgyxOaUZTL7RSsXT5f07QilqW49vS7sauKBxs0GCBMm6Q1aXKqM0EfCGzq4wkCB3nkKxGVQhYKZa2F3kcFM7uD6ThAj7qdg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746835071; c=relaxed/simple; bh=z4bdwxQ4iirtZ/jvJ9eNfsPzh7HLffleNgJOXAIIh2I=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=jOShIMzYUbkpwk88XBPvZvKyfn14HDg271DoZ1BCPbUAUqKqFDsEbahDb/IxeaVzIHFIYh1+7fGS251lS/qjgwG4sfi5h9y98tQtTu6yXUFb8VoKabYOdqppQx6EtM2A2XBxGeg3dOLUyq8+B/ILjVkH7g2xDPDg2G4ac7B3Oxs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iITW+Awe; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iITW+Awe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A0E8C4CEE4; Fri, 9 May 2025 23:57:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746835070; bh=z4bdwxQ4iirtZ/jvJ9eNfsPzh7HLffleNgJOXAIIh2I=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iITW+AweHByHjGtEP8JyDrHMmaZpMHJIohWHtBshoxEWsyyDp+AT9A0B1UvQ9OEzx uMxOVY3EMtWi8MAH7eI2fYItYSIYHD1WbUf+FAjFMyyloe/dN2F961uoV5BcVH92gQ DTsTLmhDDO1gi/89yqaW81URrwaEZBxg5nJNbM3DxUBx3WJkugt37aVT8cqVd0Ibq5 IJziFr9SsKW99/nbTxynkN1lPmjrifPAtVYzTdTbvGO0kf/4/PP7fBcCbrPDiKI5f7 j703su2lMShyhYxS7yf8QA/AUaZu8NbLTUzf1AlWYOJ3I/9pnso7CLM4EP+wyMuFea eeSqxIH3zjMVw== Date: Sat, 10 May 2025 08:57:44 +0900 From: Masami Hiramatsu (Google) To: Masami Hiramatsu (Google) Cc: paulcacheux@gmail.com, Paul Cacheux via B4 Relay , Steven Rostedt , Mathieu Desnoyers , Namhyung Kim , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] tracing: protect trace_probe_log with mutex Message-Id: <20250510085744.3dab36f6e314c9e63a673d3e@kernel.org> In-Reply-To: <20250510074456.805a16872b591e2971a4d221@kernel.org> References: <20250502-fix-trace-probe-log-race-v2-0-511ecc1521ec@gmail.com> <20250502-fix-trace-probe-log-race-v2-2-511ecc1521ec@gmail.com> <20250510074456.805a16872b591e2971a4d221@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 10 May 2025 07:44:56 +0900 Masami Hiramatsu (Google) wrote: > On Fri, 02 May 2025 15:15:53 +0200 > Paul Cacheux via B4 Relay wrote: > > > From: Paul Cacheux > > > > 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 > > --- > > 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) -- Masami Hiramatsu (Google)