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

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Message-ID: <9299a314-fd20-4255-ae4d-38ee97e16879@redhat.com>
Date: Tue, 7 Oct 2025 13:21:23 -0400
From: Waiman Long <llong@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>, Waiman Long <llong@...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>,
 Peter Zijlstra <peterz@...radead.org>, Will Deacon <will@...nel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] seqlock: introduce scoped_seqlock_read() and
 scoped_seqlock_read_irqsave()


On 10/7/25 1:18 PM, Oleg Nesterov wrote:
> On 10/07, Waiman Long wrote:
>> On 10/7/25 10:21 AM, Oleg Nesterov wrote:
>>> +
>>> +/* internal helper for scoped_seqlock_read/scoped_seqlock_read_irqsave */
>>> +static inline int
>>> +scoped_seqlock_read_retry(seqlock_t *lock, int *seq, unsigned long *flags)
>> I would suggest adding the "__" prefix to indicate that this is an internal
>> helper that shouldn't be called directly.
> OK, I will add "__", but I thought that "internal helper" makes it clear that
> it shouldn't be called directly. Nevermind, will do.
>
>>> +#define __scoped_seqlock_read(lock, lockless, seq)	\
>>> +	for (int lockless = 1, seq = read_seqbegin(lock);		\
>>> +	     lockless || scoped_seqlock_read_retry(lock, &seq, NULL);	\
>>> +	     lockless = 0)
>> I like Linus' suggestion of putting lockless and seq into a struct to make
>> it more consistent with __scoped_seqlock_read_irqsave().
> Again, will do. See my reply to Linus.
>
>>> +/**
>>> + * scoped_seqlock_read_irqsave(lock) - same as scoped_seqlock_read() but
>>> + *                                     disables irqs on a locking pass
>>> + * @lock: pointer to the seqlock_t protecting the data
>> Maybe we should we should add a comment saying that this API is similar to
>> scoped_seqlock_read() but with irqs disabled.
> Hmm... This is what the comment above tries to say... Do you think it can
> be improved?

Sorry, I missed that. Never mind :-)

Cheers,
Longman