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

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Message-ID: <0f4de435-a48e-4c4b-9c56-b7c4dc1b96cf@amd.com>
Date: Tue, 4 Mar 2025 10:52:37 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Mateusz Guzik <mjguzik@...il.com>
CC: "Sapkal, Swapnil" <swapnil.sapkal@....com>, Oleg Nesterov
	<oleg@...hat.com>, 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>, "Shenoy,
 Gautham Ranjal" <gautham.shenoy@....com>, <Neeraj.Upadhyay@....com>,
	<Ananth.narayan@....com>
Subject: Re: [PATCH] pipe_read: don't wake up the writer if the pipe is still
 full

Hello Mateusz,

On 3/4/2025 12:02 AM, K Prateek Nayak wrote:
> Hello Mateusz,
> 
> On 3/3/2025 11:24 PM, Mateusz Guzik wrote:
>> Can you guys try out the patch below?
>>
>> It changes things up so that there is no need to read 2 different vars.
>>
>> It is not the final version and I don't claim to be able to fully
>> justify the thing at the moment either, but I would like to know if it
>> fixes the problem.
> 
> Happy to help! We've queued the below patch for an overnight run, will
> report back once it is done.

Hackbench has been running for a few thousand iteration now without
experiencing any hangs yet with your changes.

> 
> Full disclaimer: We're testing on top of commit aaec5a95d596
> ("pipe_read: don't wake up the writer if the pipe is still full") where the
> issue is more reproducible. I've replaced the VFS_BUG_ON() with a plain
> BUG_ON() based on [1] since v6.14-rc1 did not include the CONFIG_DEBUG_VFS
> bits. Hope that is alright.
> 
> [1] https://lore.kernel.org/lkml/20250209185523.745956-2-mjguzik@gmail.com/
> 
> /off to get some shut eyes/
> 

-- 
Thanks and Regards,
Prateek