linux-kernel - Re: [PATCH v16 09/10] unwind deferred: Use SRCU unwind_deferred_task

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Message-ID: <20250921193527.4fef26ec@batman.local.home>
Date: Sun, 21 Sep 2025 19:35:54 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 bpf@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Jiri Olsa
 <jolsa@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung
 Kim <namhyung@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Andrii
 Nakryiko <andrii@...nel.org>, Indu Bhagat <indu.bhagat@...cle.com>, "Jose
 E. Marchesi" <jemarch@....org>, Beau Belgrave <beaub@...ux.microsoft.com>,
 Jens Remus <jremus@...ux.ibm.com>, Linus Torvalds
 <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>,
 Jens Axboe <axboe@...nel.dk>, Florian Weimer <fweimer@...hat.com>, Sam
 James <sam@...too.org>, "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH v16 09/10] unwind deferred: Use SRCU
 unwind_deferred_task_work()

On Fri, 19 Sep 2025 17:31:15 -0700
Josh Poimboeuf <jpoimboe@...nel.org> wrote:

> On Tue, Jul 29, 2025 at 02:23:13PM -0400, Steven Rostedt wrote:
> > @@ -230,6 +232,14 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
> >  	if (WARN_ON_ONCE(!CAN_USE_IN_NMI && in_nmi()))
> >  		return -EINVAL;
> >  
> > +	/* Do not allow cancelled works to request again */
> > +	bit = READ_ONCE(work->bit);
> > +	if (WARN_ON_ONCE(bit < 0))
> > +		return -EINVAL;  
> 
> The local 'bit' variable is unsigned long, so this will never be < 0.
> 
> Should be "bit == -1"?
> 

Yeah, that needs to be fixed. Thanks!

-- Steve