From: Oleg Nesterov <oleg@redhat.com>
To: Andy Lutomirski <luto@mit.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Davide Libenzi <davidel@xmailserver.org>,
Eric Dumazet <eric.dumazet@gmail.com>, Greg KH <greg@kroah.com>,
Jason Baron <jbaron@redhat.com>,
Roland McGrath <roland@hack.frob.com>,
Eugene Teo <eugeneteo@kernel.sg>,
Maxime Bizon <mbizon@freebox.fr>,
Denys Vlasenko <dvlasenk@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()
Date: Wed, 29 Feb 2012 21:06:36 +0100 [thread overview]
Message-ID: <20120229200636.GA15729@redhat.com> (raw)
In-Reply-To: <4F4E830E.3040307@mit.edu>
On 02/29, Andy Lutomirski wrote:
>
> On 02/24/2012 11:07 AM, Oleg Nesterov wrote:
> > This patch adds the special event, POLLFREE, currently only for
> > epoll. It expects that init_poll_funcptr()'ed hook should do the
> > necessary cleanup. Perhaps it should be defined as EPOLLFREE in
> > eventpoll.
>
> I have a bunch of userspace code that uses signalfd via epoll. Does
> this affect the ABI?
I hope not ;)
> Will epoll_wait ever set POLLFREE?
No.
> Does
> EPOLL_CTL_MOD accept POLLFREE?
Yes, it doesn't check the bits. EPOLL_CTL_MOD accepts any bit.
> IOW, from a userspace point of view, wtf does this do?
I hope this is transparent to the user-space. If the application
does EPOLL_CTL_MOD(POLLFREE) by mistake then ep_poll_callback(POLLFREE)
can trigger the unnecessary wakeup and move the file to ep->rdllist
but this is harmless. The subsequent ->poll() can't return POLLFREE.
Oleg.
next prev parent reply other threads:[~2012-02-29 20:13 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120222173326.GA7139@redhat.com>
2012-02-22 17:33 ` [PATCH 1/4] signalfd: introduce signalfd_cleanup() Oleg Nesterov
2012-02-22 17:34 ` [PATCH 2/4] epoll: introduce POLLFREE for ep_poll_callback() Oleg Nesterov
2012-02-22 17:34 ` [PATCH 3/4] signalfd: signalfd_cleanup() can race with remove_wait_queue() Oleg Nesterov
2012-02-22 17:35 ` [PATCH 4/4] epoll: ep_unregister_pollwait() can use the freed pwq->whead Oleg Nesterov
2012-02-23 15:44 ` Oleg Nesterov
2012-02-23 22:17 ` Linus Torvalds
2012-02-24 19:06 ` [PATCH v2 0/2] signalfd/epoll fixes Oleg Nesterov
2012-02-24 19:07 ` [PATCH v2 1/2] epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree() Oleg Nesterov
2012-02-29 19:57 ` Andy Lutomirski
2012-02-29 20:06 ` Oleg Nesterov [this message]
2012-02-29 20:16 ` Andrew Lutomirski
2012-03-01 19:26 ` Oleg Nesterov
2012-02-24 19:07 ` [PATCH v2 2/2] epoll: ep_unregister_pollwait() can use the freed pwq->whead Oleg Nesterov
2012-02-24 20:23 ` [PATCH v2 0/2] signalfd/epoll fixes Linus Torvalds
2012-02-24 23:14 ` Linus Torvalds
2012-02-25 16:08 ` Oleg Nesterov
2012-02-25 19:00 ` Linus Torvalds
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