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

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Message-ID: <cic4dekp3h5fduzsar5lydynzambabar26zjzogdbn26dxiabh@g2eaji3bqlct>
Date: Fri, 19 Sep 2025 17:31:15 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Steven Rostedt <rostedt@...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 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"?

-- 
Josh