linux-kernel - Re: [PATCH] fs/eventpoll: fix endless busy loop after timeout has expired

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Message-ID: <20250502-exzellent-hingucken-53c88d2917a1@brauner>
Date: Fri,  2 May 2025 14:22:45 +0200
From: Christian Brauner <brauner@...nel.org>
To: Max Kellermann <max.kellermann@...os.com>
Cc: Christian Brauner <brauner@...nel.org>,
	Joe Damato <jdamato@...tly.com>,
	stable@...r.kernel.org,
	viro@...iv.linux.org.uk,
	jack@...e.cz,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/eventpoll: fix endless busy loop after timeout has expired

On Tue, 29 Apr 2025 20:58:27 +0200, Max Kellermann wrote:
> After commit 0a65bc27bd64 ("eventpoll: Set epoll timeout if it's in
> the future"), the following program would immediately enter a busy
> loop in the kernel:
> 
> ```
> int main() {
>   int e = epoll_create1(0);
>   struct epoll_event event = {.events = EPOLLIN};
>   epoll_ctl(e, EPOLL_CTL_ADD, 0, &event);
>   const struct timespec timeout = {.tv_nsec = 1};
>   epoll_pwait2(e, &event, 1, &timeout, 0);
> }
> ```
> 
> [...]

I've taken this version but also credited/mentioned Joe in the commit message,
noting that I added that info

---

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] fs/eventpoll: fix endless busy loop after timeout has expired
      https://git.kernel.org/vfs/vfs/c/d9ec73301099