From: "Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
To: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Davide Libenzi <davidel-AhlLAIvw+VEjIGhXcJzhZg@public.gmane.org>,
Aaron Durbin <adurbin-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Greg Thelen <gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH 1/4] eventfd: introduce eventfd_signal_hangup()
Date: Mon, 4 Feb 2013 12:15:21 +0200 [thread overview]
Message-ID: <20130204101521.GA18322@shutemov.name> (raw)
In-Reply-To: <20130202155858.GA13022-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
On Sat, Feb 02, 2013 at 05:58:58PM +0200, Kirill A. Shutemov wrote:
> On Sat, Feb 02, 2013 at 02:50:44PM +0800, Li Zefan wrote:
> > When an eventfd is closed, a wakeup with POLLHUP will be issued,
> > but cgroup wants to issue wakeup explicitly, so when a cgroup is
> > removed userspace can be notified.
> >
> > Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Hm.. Looks like it will break eventfd semantics:
1. One eventfd can be used for deliver more then one notification from
one or more cgroups. POLLHUP on removing one of cgroups is not valid.
2. It's valid to have eventfd opened only by one userspace application. We
should not close it, just because cgroup is removed.
I think problem with multiple threads waiting an event on eventfd should
be handled in userspace.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2013-02-04 10:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-02 6:50 [PATCH 0/4] cgroup: bug fixes for eventfd Li Zefan
[not found] ` <510CB733.2080904-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-02-02 6:50 ` [PATCH 1/4] eventfd: introduce eventfd_signal_hangup() Li Zefan
[not found] ` <510CB744.7000300-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-02-02 15:58 ` Kirill A. Shutemov
[not found] ` <20130202155858.GA13022-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
2013-02-04 10:15 ` Kirill A. Shutemov [this message]
[not found] ` <20130204101521.GA18322-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
2013-02-05 3:40 ` Li Zefan
[not found] ` <51107F42.1090401-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-02-05 8:28 ` Kirill A. Shutemov
2013-02-06 1:48 ` Li Zefan
[not found] ` <5111B664.5050606-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-02-06 14:53 ` Kirill A. Shutemov
2013-02-02 6:59 ` [PATCH 0/4] cgroup: bug fixes for eventfd Li Zefan
2013-02-04 19:27 ` Tejun Heo
2013-02-02 6:51 ` [PATCH 2/4] cgroup: fix cgroup_rmdir() vs close(eventfd) race Li Zefan
[not found] ` <510CB763.3020700-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-02-02 15:59 ` Kirill A. Shutemov
2013-02-02 6:51 ` [PATCH 3/4] eventfd: make operations on eventfd return -EIDRM if it's hung up Li Zefan
2013-02-02 16:12 ` Kirill A. Shutemov
[not found] ` <20130202161229.GB12939-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
2013-02-04 3:15 ` Li Zefan
2013-02-02 6:51 ` [PATCH 4/4] cgroup: adapt to the new way of detecting cgroup removal Li Zefan
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