linux-kernel - Re: [PATCH bpf-next v1 07/22] rqspinlock: Add support for timeouts

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Message-ID: <20250107145051.GA23315@noisy.programming.kicks-ass.net>
Date: Tue, 7 Jan 2025 15:50:51 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	Barret Rhoden <brho@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Waiman Long <llong@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Martin KaFai Lau <martin.lau@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>, Tejun Heo <tj@...nel.org>,
	Josh Don <joshdon@...gle.com>, Dohyun Kim <dohyunkim@...gle.com>,
	kernel-team@...a.com
Subject: Re: [PATCH bpf-next v1 07/22] rqspinlock: Add support for timeouts

On Tue, Jan 07, 2025 at 05:59:49AM -0800, Kumar Kartikeya Dwivedi wrote:
> +struct rqspinlock_timeout {
> +	u64 timeout_end;
> +	u64 duration;
> +	u16 spin;
> +};

> +#define RES_CHECK_TIMEOUT(ts, ret)                    \
> +	({                                            \
> +		if (!((ts).spin++ & 0xffff))          \

Per the above spin is a u16, this mask is pointless.

> +			(ret) = check_timeout(&(ts)); \
> +		(ret);                                \
> +	})