linux-kernel - Re: [PATCH v2 1/4] seqlock: introduce scoped_seqlock_read() and scoped_seqlock_read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251008125508.GJ3289052@noisy.programming.kicks-ass.net>
Date: Wed, 8 Oct 2025 14:55:08 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Boqun Feng <boqun.feng@...il.com>,
	David Howells <dhowells@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Li RongQing <lirongqing@...du.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] seqlock: introduce scoped_seqlock_read() and
 scoped_seqlock_read_irqsave()

On Wed, Oct 08, 2025 at 02:30:45PM +0200, Oleg Nesterov wrote:
> The read_seqbegin/need_seqretry/done_seqretry API is cumbersome and
> error prone. With the new helper the "typical" code like
> 
> 	int seq, nextseq;
> 	unsigned long flags;
> 
> 	nextseq = 0;
> 	do {
> 		seq = nextseq;
> 		flags = read_seqbegin_or_lock_irqsave(&seqlock, &seq);
> 
> 		// read-side critical section
> 
> 		nextseq = 1;
> 	} while (need_seqretry(&seqlock, seq));
> 	done_seqretry_irqrestore(&seqlock, seq, flags);
> 
> can be rewritten as
> 
> 	scoped_seqlock_read_irqsave (&seqlock) {
> 		// read-side critical section
> 	}
> 

Hmm, on first reading I was expecting that to be:

	do {
		seq = read_seqbegin(&seqlock);

		// read-side section

	} while (read_seqretry(&seqlock, seq));

for lack of that _or_lock() wording, but I suppose we can make that
something like:

 	scoped_seqbegin_read (&seqlock) {
		// read-side section
	}

which is distinctive enough.