linux-kernel - RE: [PATCH] pipe: Make a partially-satisfied blocking read wait for more

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Message-ID: <fa6de786ee1241c6ba54c3cce0b980aa@AcuMS.aculab.com>
Date:   Mon, 26 Jun 2023 09:31:52 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>
CC:     Franck Grosjean <fgrosjea@...hat.com>,
        Phil Auld <pauld@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] pipe: Make a partially-satisfied blocking read wait for
 more

From: Linus Torvalds
> Sent: 23 June 2023 23:42
> 
> On Fri, 23 Jun 2023 at 15:34, David Howells <dhowells@...hat.com> wrote:
> >
> > Can you consider merging something like the attached patch?  Unfortunately,
> > there are applications out there that depend on a read from pipe() waiting
> > until the buffer is full under some circumstances.  Patch a28c8b9db8a1
> > removed the conditionality on there being an attached writer.
> 
> This patch seems actively wrong, in that now it's possibly waiting for
> data that won't come, even if it's nonblocking.

I think it pretty much breaks:
	command | tee file
where 'command' is careful to fflush(stdout).

	David

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