linux-kernel - Re: [PATCH] pipe_read: don't wake up the writer if the pipe is still full

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Message-ID: <20250226181220.GJ8995@redhat.com>
Date: Wed, 26 Feb 2025 19:12:20 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: "Sapkal, Swapnil" <swapnil.sapkal@....com>
Cc: Manfred Spraul <manfred@...orfullife.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christian Brauner <brauner@...nel.org>,
	David Howells <dhowells@...hat.com>,
	WangYuli <wangyuli@...ontech.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	K Prateek Nayak <kprateek.nayak@....com>,
	"Shenoy, Gautham Ranjal" <gautham.shenoy@....com>,
	Neeraj.Upadhyay@....com, mjguzik@...il.com
Subject: Re: [PATCH] pipe_read: don't wake up the writer if the pipe is still
 full

On 02/26, Sapkal, Swapnil wrote:
>
> >Can you reproduce with "--process" rather than "--threads" ?
> >
> I was able to reproduce the issue with processes also. Total 33 processes
> were sleeping out of which 20 were readers and 13 were writers.

Thanks a lot. I am wondering what makes your machine (or .config?)
special ;) A lot of people and robots tested this patch with these
options.

> The stack trace for main hackbench process is as follows:
>
> [<0>] do_wait+0xb5/0x110

Yes, this is clear, the main thread/process is not interesting.

> I am trying to reproduce the issue with suggestions by Mateusz.

Great.

So far I still have no clue. Most probably I will ask you to do
more testing after that, perhaps with some debugging patches.

Thanks again for your help,

Oleg.