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From: Sandeep Patil <>
To: Linus Torvalds <>
Cc: linux-fsdevel <>,
	Linux Kernel Mailing List <>,
	David Howells <>,
	Greg Kroah-Hartman <>,
	stable <>,
	Android Kernel Team <>
Subject: Re: [PATCH 1/1] fs: pipe: wakeup readers everytime new data written is to pipe
Date: Fri, 30 Jul 2021 19:47:22 +0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 7/30/21 7:23 PM, Linus Torvalds wrote:
> On Fri, Jul 30, 2021 at 12:11 PM Sandeep Patil <> wrote:
>> Yes, your patch fixes all apps on Android I can test that include this
>> library.
> Ok, thanks for checking.
>> fwiw, the library seems to have been fixed. However, I am not sure
>> how long it will be for all apps to take that update :(.
> I wonder if I could make the wakeup logic do this only for the epollet case.

aren't we supposed to wakeup on each write in level-triggered (default) 
case though?

> I'll have to think about it, but maybe I'll just apply that simple
> patch. I dislike the pointless wakeups, and as long as the only case I
> knew of was only a test of broken behavior, it was fine. But now that
> you've reported actual application breakage, this is in the "real
> regression" category, and so I'll fix it one way or the other.
> And on the other hand I also have a slight preference towards your
> patch simply because you did the work of finding this out, so you
> should get the credit.

Ha, I can't really claim credit here. This was also reported to us
in Android that triggered the search. Plus, now that I see your thread 
with Michael Kerrisk, he was way ahead of us in finding this out.

> I'll mull it over a bit more, but whatever I'll do I'll do before rc4
> and mark it for stable.

Thanks, I was actually going to suggest taking your patch cause it also 
  makes changes in pipe_read(). I am not sure if there are apps that do 
EPOLLET | EPOLLOUT (can't think of a reason why).

- ssp

> Thanks for testing,
>                   Linus

  reply	other threads:[~2021-07-30 19:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 22:26 [PATCH 0/1] Revert change in pipe reader wakeup behavior Sandeep Patil
2021-07-29 22:26 ` [PATCH 1/1] fs: pipe: wakeup readers everytime new data written is to pipe Sandeep Patil
2021-07-29 23:01   ` Linus Torvalds
2021-07-30 19:11     ` Sandeep Patil
2021-07-30 19:23       ` Linus Torvalds
2021-07-30 19:47         ` Sandeep Patil [this message]
2021-07-30 22:06           ` Linus Torvalds
2021-07-30 22:53         ` Linus Torvalds
2021-07-30 22:55           ` Linus Torvalds
2021-07-31  5:32             ` Greg Kroah-Hartman
2021-08-02 18:59           ` Sandeep Patil

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