linux-kernel - Re: The thundering herd like problem when multi epolls on one fd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20120114155713.GA2966@hell>
Date:	Sat, 14 Jan 2012 16:57:13 +0100
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Li Yu <raise.sail@...il.com>, linux-kernel@...r.kernel.org,
	davidel@...ilserver.org
Subject: Re: The thundering herd like problem when multi epolls on one fd

* Eric Dumazet | 2012-01-14 14:20:47 [+0100]:

>What happens if the awaken thread does not consume the event, and prefer
>to exit ?
>
>If several threads are doing select()/poll()/epoll() on a shared fd,
>they _all_ must be notified the fd is ready, as manpages claim.
>

And if it is intended? Signaled via a new epoll_ctl() epoll_event flag? E.g.
EPOLLEXCLUSIVE

>Doing otherwise would require the prior consent of the user, using a
>special flag for example, and documentation.

Oops, yes. A fanout like mechanism _may be_ superior, but I think tests will
show some improvements anyway.

Hagen
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/