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From: Christian Brauner <brauner@kernel.org>
To: Max Kellermann <max.kellermann@ionos.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: When to lock pipe->rd_wait.lock?
Date: Wed, 20 Sep 2023 17:50:26 +0200	[thread overview]
Message-ID: <20230920-kabine-senden-e1a137f3d7cc@brauner> (raw)
In-Reply-To: <CAKPOu+9uO=wbTnesZ-jCw5E+AY1fwvcXykBtEQYOzHTyEeP_8g@mail.gmail.com>

On Wed, Sep 20, 2023 at 05:21:03PM +0200, Max Kellermann wrote:
> On Wed, Sep 20, 2023 at 3:30 PM Christian Brauner <brauner@kernel.org> wrote:
> > Afaict, the mutex is sufficient protection unless you're using
> > watchqueues which use post_one_notification() that cannot acquire the
> > pipe mutex. Since splice operations aren't supported on such kernel
> > notification pipes - see get_pipe_info() - it should be unproblematic.
> 
> Which means that the spinlocks can safely be removed from
> pipe_write(), because they are unnecessary overhead?

I don't think so, O_NOTIFICATION/watch queue pipes allow userspace to
use pipe_read() and pipe_write() but prevent the usage of splice. The
spinlock is there for post_one_notification() which is called from
kernel context.

  reply	other threads:[~2023-09-20 15:50 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-20 12:34 When to lock pipe->rd_wait.lock? Max Kellermann
2023-09-20 13:30 ` Christian Brauner
2023-09-20 15:21   ` Max Kellermann
2023-09-20 15:50     ` Christian Brauner [this message]
2023-09-20 16:14       ` Max Kellermann
2023-09-21  7:28   ` Max Kellermann
2023-09-21  8:05     ` Max Kellermann
2023-09-21  9:17       ` Christian Brauner
2023-09-21  9:38         ` Max Kellermann

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