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 34D31253B60; Wed, 19 Mar 2025 13:29:57 +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=1742390999; cv=none; b=B6oHiLkd8/BwOytLxkGpVMpeytGCcQMz2w1pc/V0DD55PejsObIq5CALF+8aYvQfFflQBaNU57/l+litnS5uKxKQD9YhPrXV0jTs4vqvHgkYTOvUYJOzmIPb479DNzKVqFbAfYwFvn3fMjT9zb05uHuoyUNH7PW0qBGZNmxgZYc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742390999; c=relaxed/simple; bh=L3zkG5wkdf9levIxPwOzxunDMgNfSmvM+Dhstn7lFMs=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=r5EPCTglQE9zJcGsc02h9v0+6x1xA5/9vjj1qN4DVE3LwOfCy0xlDcBetiKU534cy9qgP6CeoWRNk1M3RAb+xXDtf1Kcos56BA1DiFlLs0SbyKHi6pS8jZe2n9u0EOhfTyzOyoCeFBhi5deE6KbzBm3e3+g/7TBXtqtFIAAVQw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z5LvZbzD; 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="Z5LvZbzD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 290CDC4CEE9; Wed, 19 Mar 2025 13:29:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742390997; bh=L3zkG5wkdf9levIxPwOzxunDMgNfSmvM+Dhstn7lFMs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Z5LvZbzDHkwilSgVWZ5dAnzNuav8+5oNYdF/MIr7MBiXYz3MuPO3YRoq12u5YC4vg nHlJztUkZWG2rplLgMB2Y3prRqiOm9MGkgT5Bnbb20VlskXgYq1zL2GYEkv6bPEoT2 iOBIRE76JyX9Y9qxc2qszU8mu3Yso9k3njeC9ruOqmH1QIaPtyqr4JTMGezfAjeLov FzCYbB/oprB8y/lMg4XKfS4/Mof45vnb5X2wUSLk4AsVY1kIZkQCdBXbs09QdM4eAt tBdpOxSBa/E+ayPilaML2LRylEoiuYWtolxiKzrlMqKFa5sTHOB3KJV7s9Y0p77Pp8 uBNTtQnoZrtIQ== Date: Wed, 19 Mar 2025 22:29:53 +0900 From: Masami Hiramatsu (Google) To: Douglas RAILLARD Cc: rostedt@goodmis.org, Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH] tracing: Ensure module defining synth event cannot be unloaded while tracing Message-Id: <20250319222953.3c741b520a8686c8e0a9b1d9@kernel.org> In-Reply-To: <20250318180906.226841-1-douglas.raillard@arm.com> References: <20250318180906.226841-1-douglas.raillard@arm.com> 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 Tue, 18 Mar 2025 18:09:05 +0000 Douglas RAILLARD wrote: > From: Douglas Raillard > > Currently, using synth_event_delete() will fail if the event is being > used (tracing in progress), but that is normally done in the module exit > function. At that stage, failing is problematic as returning a non-zero > status means the module will become locked (impossible to unload or > reload again). > > Instead, ensure the module exit function does not get called in the > first place by increasing the module refcnt when the event is enabled. > OK, I think this is correct way to fix that scenario. Acked-by: Masami Hiramatsu (Google) Thank you, > Signed-off-by: Douglas Raillard > --- > kernel/trace/trace_events_synth.c | 30 +++++++++++++++++++++++++++++- > 1 file changed, 29 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c > index e3f7d09e5512..bb7ef6e76991 100644 > --- a/kernel/trace/trace_events_synth.c > +++ b/kernel/trace/trace_events_synth.c > @@ -852,6 +852,34 @@ static struct trace_event_fields synth_event_fields_array[] = { > {} > }; > > +static int synth_event_reg(struct trace_event_call *call, > + enum trace_reg type, void *data) > +{ > + struct synth_event *event = container_of(call, struct synth_event, call); > + > + switch (type) { > + case TRACE_REG_REGISTER: > + case TRACE_REG_PERF_REGISTER: > + if (!try_module_get(event->mod)) > + return -EBUSY; > + break; > + default: > + break; > + } > + > + int ret = trace_event_reg(call, type, data); > + > + switch (type) { > + case TRACE_REG_UNREGISTER: > + case TRACE_REG_PERF_UNREGISTER: > + module_put(event->mod); > + break; > + default: > + break; > + } > + return ret; > +} > + > static int register_synth_event(struct synth_event *event) > { > struct trace_event_call *call = &event->call; > @@ -881,7 +909,7 @@ static int register_synth_event(struct synth_event *event) > goto out; > } > call->flags = TRACE_EVENT_FL_TRACEPOINT; > - call->class->reg = trace_event_reg; > + call->class->reg = synth_event_reg; > call->class->probe = trace_event_raw_event_synth; > call->data = event; > call->tp = event->tp; > -- > 2.43.0 > -- Masami Hiramatsu (Google)