linux-kernel - RE: Weird issue with epoll and kernel >= 5.0

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Date:   Sun, 29 Mar 2020 12:09:16 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Randy Dunlap' <rdunlap@...radead.org>,
        Omar Kilani <omar.kilani@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Davidlohr Bueso <dave@...olabs.net>
Subject: RE: Weird issue with epoll and kernel >= 5.0

From: Randy Dunlap
> Sent: 28 March 2020 19:22
...
> There have been around 10 changes in fs/eventpoll.c since v5.0 was
> released in March, 2019, so it would be helpful if you could test
> the latest mainline kernel to see if the problem is still present.

Is there any info about the scenarios that the fixes affect?
We've an application that can use epoll() or poll() and I wonder
if I should not default to epoll() on 5.0+ kernels that might be dodgy.

It rather depends whether wakeups just get lost - but the next
rx data will wake things up, or whether the linked lists get
completely hosed and 'all hell' breaks out (or doesn't).

In our case there is only one reader and the fd are all
UDP sockets (added and removed when the socket is created/closed).

	David

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