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From: Eric Biggers <ebiggers@kernel.org>
To: Siddh Raman Pant <code@siddh.me>
Cc: christophe.jaillet@wanadoo.fr, corbet@lwn.net,
	dhowells@redhat.com, edumazet@google.com,
	linux-kernel-mentees@lists.linuxfoundation.org,
	linux-kernel@vger.kernel.org, mchehab@kernel.org,
	rdunlap@infradead.org
Subject: Re: [PATCH v2 3/3] kernel/watch_queue: Remove wqueue->defunct and use pipe for clear check
Date: Fri, 5 Aug 2022 00:24:31 -0700	[thread overview]
Message-ID: <YuzFrzrTnTtUHMn/@sol.localdomain> (raw)
In-Reply-To: <20220804144152.468916-1-code@siddh.me>

On Thu, Aug 04, 2022 at 08:11:52PM +0530, Siddh Raman Pant wrote:
>  static inline bool lock_wqueue(struct watch_queue *wqueue)
>  {
>  	spin_lock_bh(&wqueue->lock);
> -	if (unlikely(wqueue->defunct)) {
> +	if (unlikely(!READ_ONCE(wqueue->pipe))) {
>  		spin_unlock_bh(&wqueue->lock);
>  		return false;
>  	}

Why is the READ_ONCE() needed?  Doesn't wqueue->lock protect wqueue->pipe?

> +	/* This pipe will get freed by the caller free_pipe_info().
> +	 * Removing this reference also prevents new notifications.
> +	 */

This isn't the correct block comment format; it should look like:

	/*
	 * This pipe will get freed by the caller free_pipe_info().
	 * Removing this reference also prevents new notifications.
	 */

- Eric

WARNING: multiple messages have this Message-ID (diff)
From: Eric Biggers <ebiggers@kernel.org>
To: Siddh Raman Pant <code@siddh.me>
Cc: corbet@lwn.net, rdunlap@infradead.org,
	linux-kernel@vger.kernel.org, dhowells@redhat.com,
	edumazet@google.com, christophe.jaillet@wanadoo.fr,
	mchehab@kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH v2 3/3] kernel/watch_queue: Remove wqueue->defunct and use pipe for clear check
Date: Fri, 5 Aug 2022 00:24:31 -0700	[thread overview]
Message-ID: <YuzFrzrTnTtUHMn/@sol.localdomain> (raw)
In-Reply-To: <20220804144152.468916-1-code@siddh.me>

On Thu, Aug 04, 2022 at 08:11:52PM +0530, Siddh Raman Pant wrote:
>  static inline bool lock_wqueue(struct watch_queue *wqueue)
>  {
>  	spin_lock_bh(&wqueue->lock);
> -	if (unlikely(wqueue->defunct)) {
> +	if (unlikely(!READ_ONCE(wqueue->pipe))) {
>  		spin_unlock_bh(&wqueue->lock);
>  		return false;
>  	}

Why is the READ_ONCE() needed?  Doesn't wqueue->lock protect wqueue->pipe?

> +	/* This pipe will get freed by the caller free_pipe_info().
> +	 * Removing this reference also prevents new notifications.
> +	 */

This isn't the correct block comment format; it should look like:

	/*
	 * This pipe will get freed by the caller free_pipe_info().
	 * Removing this reference also prevents new notifications.
	 */

- Eric
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Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

  reply	other threads:[~2022-08-05  7:24 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-04 13:30 [PATCH 0/3] kernel/watch_queue: Clean up some code Siddh Raman Pant via Linux-kernel-mentees
2022-08-04 13:30 ` Siddh Raman Pant
2022-08-04 13:30 ` [PATCH 1/3 v4] kernel/watch_queue: Remove dangling pipe reference while clearing watch_queue Siddh Raman Pant via Linux-kernel-mentees
2022-08-04 13:30   ` Siddh Raman Pant
2022-08-04 13:30 ` [PATCH 2/3] kernel/watch_queue: Improve struct annotation formatting Siddh Raman Pant via Linux-kernel-mentees
2022-08-04 13:30   ` Siddh Raman Pant
2022-08-05  7:22   ` Eric Biggers
2022-08-05  7:22     ` Eric Biggers
2022-08-05  9:35     ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-05  9:35       ` Siddh Raman Pant
2022-08-04 13:30 ` [PATCH 3/3] kernel/watch_queue: Remove wqueue->defunct and use pipe for clear check Siddh Raman Pant via Linux-kernel-mentees
2022-08-04 13:30   ` Siddh Raman Pant
2022-08-04 14:41   ` [PATCH v2 " Siddh Raman Pant via Linux-kernel-mentees
2022-08-04 14:41     ` Siddh Raman Pant
2022-08-05  7:24     ` Eric Biggers [this message]
2022-08-05  7:24       ` Eric Biggers
2022-08-05  9:35       ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-05  9:35         ` Siddh Raman Pant
2022-08-05 18:33         ` Eric Biggers
2022-08-05 18:33           ` Eric Biggers
2022-08-06  7:23           ` Siddh Raman Pant
2022-08-06  7:23             ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-05  7:16 ` [PATCH 0/3] kernel/watch_queue: Clean up some code Eric Biggers
2022-08-05  7:16   ` Eric Biggers
2022-08-05  9:35   ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-05  9:35     ` Siddh Raman Pant

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