linux-kernel - Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE

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Message-ID: <20260113135616.xt2Nm4IY@linutronix.de>
Date: Tue, 13 Jan 2026 14:56:16 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux trace kernel <linux-trace-kernel@...r.kernel.org>,
	bpf@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of
 __DO_TRACE_CALL() with SRCU-fast

On 2026-01-09 13:58:21 [-0500], Mathieu Desnoyers wrote:
> On 2026-01-09 12:21, Steven Rostedt wrote:
> > > Using SRCU-fast to protect tracepoint callback iteration makes sense
> > > for preempt-rt, but I'd recommend moving the migrate disable guard
> > > within the bpf callback code rather than slowing down other tracers
> > > which execute within a short amount of time. Other tracers can then
> > > choose to disable preemption rather than migration if that's a better
> > > fit for their needs.
> > 
> > This is a discussion with the BPF folks.
> 
> FWIW, the approach I'm proposing would be similar to what I've done for
> faultable syscall tracepoints.

I just started reading this thread but we could limit the
migrate_disable() to only the BPF callback part so it does not effect
the whole tracepoint if there not a BFP program attached to it.

Sebastian