linux-kernel - Re: [PATCH v4 5/5] tracing: convert sys

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Message-ID: <2dca3126-5bbd-4d86-a888-b532174ae6f1@efficios.com>
Date: Thu, 20 Jun 2024 11:05:42 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
 Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org,
 Michael Jeanson <mjeanson@...icios.com>, Alexei Starovoitov
 <ast@...nel.org>, Yonghong Song <yhs@...com>,
 "Paul E . McKenney" <paulmck@...nel.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
 bpf@...r.kernel.org, Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH v4 5/5] tracing: convert sys_enter/exit to faultable
 tracepoints

On 2023-11-20 16:46, Peter Zijlstra wrote:
> On Mon, Nov 20, 2023 at 03:54:18PM -0500, Mathieu Desnoyers wrote:
> 
>> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
>> index de753403cdaf..718a0723a0bc 100644
>> --- a/kernel/trace/trace_syscalls.c
>> +++ b/kernel/trace/trace_syscalls.c
>> @@ -299,27 +299,33 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
>>   	int syscall_nr;
>>   	int size;
>>   
>> +	/*
>> +	 * Probe called with preemption enabled (may_fault), but ring buffer and
>> +	 * per-cpu data require preemption to be disabled.
>> +	 */
>> +	preempt_disable_notrace();
> 
> 	guard(preempt_notrace)();
> 
> and ditch all the goto crap.

[ more guard stuff ]

Sure, will do, thanks!

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com