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From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Jason Baron <jbaron@akamai.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Al Viro <viro@ftp.linux.org.uk>,
	Eric Wong <normalperson@yhbt.net>,
	Madars Vitolins <m@silodev.com>, Jonathan Corbet <corbet@lwn.net>,
	Andy Lutomirski <luto@amacapital.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Hagen Paul Pfeifer <hagen@jauu.net>,
	lkml <linux-kernel@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH] epoll: add exclusive wakeups flag
Date: Fri, 11 Mar 2016 21:30:49 +0100	[thread overview]
Message-ID: <CAKgNAkgb-2omfCc=oBr66_CViJjBQ6=3vNfES99m6ZQ7g36p2Q@mail.gmail.com> (raw)
In-Reply-To: <56E1DBC2.6040109@akamai.com>

>> By the way, in the code you have
>>
>>         case EPOLL_CTL_MOD:
>>                 if (epi) {
>>                         if (!(epi->event.events & EPOLLEXCLUSIVE)) {
>>                                 epds.events |= POLLERR | POLLHUP;
>>                                 error = ep_modify(ep, epi, &epds);
>>                         }
>>
>> I think the "if" here is redundant. IIUC, earlier in the code you
>> disallow EPOLL_CTL_MOD with EPOLLEXCLUSIVE.
>>
>> Cheers,
>>
>> Michael
>>
>>
>
> Hi Michael,
>
> So the previous check ensures that you can not add the EPOLLEXCLUSIVE
> flag to the events via an EPOLL_CTL_MOD operation, where EPOLLEXCLUSIVE
> may not be the existing events set. While this check here ensure you
> can't modify an existing set that already has the EPOLLEXCLUSIVE flag.

Hmmm - I misread the code, itr seems :-/. Could you please carefully
check the man page text I sent earlier in this thread. Maybe I
injected some errors into the text.

Thanks,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

WARNING: multiple messages have this Message-ID (diff)
From: "Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Jason Baron <jbaron-JqFfY2XvxFXQT0dZR+AlfA@public.gmane.org>
Cc: Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	Al Viro <viro-rfM+Q5joDG/XmaaqVzeoHQ@public.gmane.org>,
	Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org>,
	Madars Vitolins <m@silodev.com>,
	Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>,
	Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
	Linus Torvalds
	<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Hagen Paul Pfeifer <hagen-GvnIQ6b/HdU@public.gmane.org>,
	lkml <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH] epoll: add exclusive wakeups flag
Date: Fri, 11 Mar 2016 21:30:49 +0100	[thread overview]
Message-ID: <CAKgNAkgb-2omfCc=oBr66_CViJjBQ6=3vNfES99m6ZQ7g36p2Q@mail.gmail.com> (raw)
In-Reply-To: <56E1DBC2.6040109-JqFfY2XvxFXQT0dZR+AlfA@public.gmane.org>

>> By the way, in the code you have
>>
>>         case EPOLL_CTL_MOD:
>>                 if (epi) {
>>                         if (!(epi->event.events & EPOLLEXCLUSIVE)) {
>>                                 epds.events |= POLLERR | POLLHUP;
>>                                 error = ep_modify(ep, epi, &epds);
>>                         }
>>
>> I think the "if" here is redundant. IIUC, earlier in the code you
>> disallow EPOLL_CTL_MOD with EPOLLEXCLUSIVE.
>>
>> Cheers,
>>
>> Michael
>>
>>
>
> Hi Michael,
>
> So the previous check ensures that you can not add the EPOLLEXCLUSIVE
> flag to the events via an EPOLL_CTL_MOD operation, where EPOLLEXCLUSIVE
> may not be the existing events set. While this check here ensure you
> can't modify an existing set that already has the EPOLLEXCLUSIVE flag.

Hmmm - I misread the code, itr seems :-/. Could you please carefully
check the man page text I sent earlier in this thread. Maybe I
injected some errors into the text.

Thanks,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

  reply	other threads:[~2016-03-11 20:31 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-08  3:23 [PATCH] epoll: add exclusive wakeups flag Jason Baron
2015-12-08  3:23 ` [PATCH] epoll: add EPOLLEXCLUSIVE flag Jason Baron
2015-12-08  3:23   ` Jason Baron
2016-01-28  7:16 ` [PATCH] epoll: add exclusive wakeups flag Michael Kerrisk (man-pages)
2016-01-28  7:16   ` Michael Kerrisk (man-pages)
2016-01-28 17:57   ` Jason Baron
2016-01-29  8:14     ` Michael Kerrisk (man-pages)
2016-02-01 19:42       ` Jason Baron
2016-02-01 19:42         ` Jason Baron
2016-03-10 18:53       ` Jason Baron
2016-03-10 19:47         ` Michael Kerrisk (man-pages)
2016-03-10 19:47           ` Michael Kerrisk (man-pages)
2016-03-10 19:58         ` Michael Kerrisk (man-pages)
2016-03-10 19:58           ` Michael Kerrisk (man-pages)
2016-03-10 20:40           ` Jason Baron
2016-03-10 20:40             ` Jason Baron
2016-03-11 20:30             ` Michael Kerrisk (man-pages) [this message]
2016-03-11 20:30               ` Michael Kerrisk (man-pages)
     [not found]               ` <56E32FC5.4030902@akamai.com>
     [not found]                 ` <56E353CF.6050503@gmail.com>
     [not found]                   ` <56E6D0ED.20609@akamai.com>
2016-03-14 17:47                     ` Michael Kerrisk (man-pages)
2016-03-14 19:32                       ` Jason Baron
2016-03-14 19:32                         ` Jason Baron
2016-03-14 20:01                         ` Michael Kerrisk (man-pages)
2016-03-14 20:01                           ` Michael Kerrisk (man-pages)
2016-03-14 21:03                           ` Michael Kerrisk (man-pages)
2016-03-14 21:03                             ` Michael Kerrisk (man-pages)
2016-03-14 22:35                             ` Jason Baron
2016-03-14 23:09                               ` Madars Vitolins
2016-03-14 23:26                               ` Michael Kerrisk (man-pages)
2016-03-14 23:26                                 ` Michael Kerrisk (man-pages)
2016-03-15  2:36                                 ` Jason Baron
2016-03-15  2:36                                   ` Jason Baron

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