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References: <1299681411-9227-1-git-send-email-virtuoso@slind.org> <20110309162513.5058c824.akpm@linux-foundation.org>
From: Kay Sievers <kay.sievers@vrfy.org>
Date: Thu, 10 Mar 2011 01:36:18 +0100
Message-ID: <AANLkTinZioShsr3O0Z=xaEQ-S=JBCgs_SS_LdsBnNhZ2@mail.gmail.com>
Subject: Re: [RFCv4] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock changes
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Shishkin <virtuoso@slind.org>, linux-kernel@vger.kernel.org,
        Ken MacLeod <ken@bitsko.slc.ut.us>,
        Shaun Reich <predator106@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@suse.de>, Feng Tang <feng.tang@intel.com>,
        Michael Tokarev <mjt@tls.msk.ru>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        John Stultz <johnstul@us.ibm.com>,
        Chris Friesen <chris.friesen@genband.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Artem Bityutskiy <dedekind1@gmail.com>,
        Davide Libenzi <davidel@xmailserver.org>,
        linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
        Michael Kerrisk <mtk.manpages@gmail.com>
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On Thu, Mar 10, 2011 at 01:25, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed,  9 Mar 2011 16:36:51 +0200
> Alexander Shishkin <virtuoso@slind.org> wrote:
>
>> Changes since v3:
>>  - changed timerfd_settime() semantics (see below)
>> Changes since v2:
>>  - replaced sysfs interface with a syscall
>>  - added sysctl/procfs handle to set a limit to the number of users
>>  - fixed issues pointed out by Greg.
>> Changes since v1:
>>  - updated against 2.6.36-rc1,
>>  - added notification/filtering options,
>>  - added Documentation/ABI/sysfs-kernel-time-notify interface description.

> It would be helpful to know if the identified users of this feature
> actually find it useful and adequate.  I guess the most common
> application is the 1,001 desktop clock widgets.  Do you have any
> feedback from any of the owners of those?

We want it for systemd, to provide cron-like functionality but without
the need to stupidly wake up every minute and check the system time
for possible jumps.

It also sounds useful for a generic resume (after system suspend)
notification for applications, which isn't really possible today.

Kay
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