From: "Theodore Ts'o" <tytso@mit.edu>
To: Kent Overstreet <koverstreet@google.com>
Cc: linux-kernel@vger.kernel.org, linux-aio@kvack.org,
akpm@linux-foundation.org, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@elte.hu>, Zach Brown <zab@redhat.com>,
Felipe Balbi <balbi@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mark Fasheh <mfasheh@suse.com>, Joel Becker <jlbec@evilplan.org>,
Rusty Russell <rusty@rustcorp.com.au>,
Jens Axboe <axboe@kernel.dk>,
Asai Thambi S P <asamymuthupa@micron.com>,
Selvan Mani <smani@micron.com>,
Sam Bradshaw <sbradshaw@micron.com>,
Jeff Moyer <jmoyer@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
Benjamin LaHaise <bcrl@kvack.org>
Subject: Re: [PATCH 13/33] wait: add wait_event_hrtimeout()
Date: Mon, 1 Apr 2013 21:43:53 -0400 [thread overview]
Message-ID: <20130402014353.GB30122@thunk.org> (raw)
In-Reply-To: <1363883754-27966-14-git-send-email-koverstreet@google.com>
On Thu, Mar 21, 2013 at 09:35:34AM -0700, Kent Overstreet wrote:
> Analagous to wait_event_timeout() and friends, this adds
> wait_event_hrtimeout() and wait_event_interruptible_hrtimeout().
>
> Note that unlike the versions that use regular timers, these don't return
> the amount of time remaining when they return - instead, they return 0 or
> -ETIME if they timed out. because I was uncomfortable with the semantics
> of doing it the other way (that I could get it right, anyways).
>
> If the timer expires, there's no real guarantee that expire_time -
> current_time would be <= 0 - due to timer slack certainly, and I'm not
> sure I want to know the implications of the different clock bases in
> hrtimers.
>
> If the timer does expire and the code calculates that the time remaining
> is nonnegative, that could be even worse if the calling code then reuses
> that timeout. Probably safer to just return 0 then, but I could imagine
> weird bugs or at least unintended behaviour arising from that too.
>
> I came to the conclusion that if other users end up actually needing the
> amount of time remaining, the sanest thing to do would be to create a
> version that uses absolute timeouts instead of relative.
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
next prev parent reply other threads:[~2013-04-02 1:44 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-21 16:35 [PATCH 00/33] AIO cleanups/performance improvements Kent Overstreet
2013-03-21 16:35 ` [PATCH 01/33] mm: remove old aio use_mm() comment Kent Overstreet
2013-03-28 14:13 ` Theodore Ts'o
2013-04-12 15:42 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 02/33] aio: remove dead code from aio.h Kent Overstreet
2013-03-28 14:13 ` Theodore Ts'o
2013-04-12 15:42 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 03/33] gadget: remove only user of aio retry Kent Overstreet
2013-03-21 16:42 ` Felipe Balbi
2013-04-12 15:42 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 04/33] aio: remove retry-based AIO Kent Overstreet
2013-03-28 14:20 ` Theodore Ts'o
2013-04-12 15:43 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 05/33] char: add aio_{read,write} to /dev/{null,zero} Kent Overstreet
2013-03-28 14:20 ` Theodore Ts'o
2013-04-12 15:43 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 06/33] aio: kill return value of aio_complete() Kent Overstreet
2013-03-28 14:22 ` Theodore Ts'o
2013-04-12 15:44 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 07/33] aio: add kiocb_cancel() Kent Overstreet
2013-03-28 14:54 ` Theodore Ts'o
2013-04-12 15:58 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 08/33] aio: move private stuff out of aio.h Kent Overstreet
2013-03-29 16:07 ` Theodore Ts'o
2013-04-12 15:59 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 09/33] aio: dprintk() -> pr_debug() Kent Overstreet
2013-03-21 17:38 ` Joe Perches
2013-03-29 16:17 ` Theodore Ts'o
2013-04-12 16:01 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 10/33] aio: do fget() after aio_get_req() Kent Overstreet
2013-03-29 16:48 ` Theodore Ts'o
2013-04-12 16:51 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 11/33] aio: make aio_put_req() lockless Kent Overstreet
2013-03-29 17:14 ` Theodore Ts'o
2013-04-12 21:01 ` Jeff Moyer
2013-03-21 16:35 ` [PATCH 12/33] aio: refcounting cleanup Kent Overstreet
2013-04-02 1:32 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 13/33] wait: add wait_event_hrtimeout() Kent Overstreet
2013-04-02 1:43 ` Theodore Ts'o [this message]
2013-03-21 16:35 ` [PATCH 14/33] aio: make aio_read_evt() more efficient, convert to hrtimers Kent Overstreet
2013-04-02 1:58 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 15/33] aio: use flush_dcache_page() Kent Overstreet
2013-04-02 2:12 ` Theodore Ts'o
2013-04-09 21:07 ` Kent Overstreet
2013-03-21 16:35 ` [PATCH 16/33] aio: use cancellation list lazily Kent Overstreet
2013-04-02 2:36 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 17/33] aio: change reqs_active to include unreaped completions Kent Overstreet
2013-04-02 2:53 ` Theodore Ts'o
2013-04-02 15:47 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 18/33] aio: kill batch allocation Kent Overstreet
2013-04-02 3:03 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 19/33] aio: kill struct aio_ring_info Kent Overstreet
2013-04-02 3:26 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 20/33] aio: give shared kioctx fields their own cachelines Kent Overstreet
2013-04-02 3:27 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 21/33] aio: reqs_active -> reqs_available Kent Overstreet
2013-04-02 15:48 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 22/33] aio: percpu reqs_available Kent Overstreet
2013-04-02 16:03 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 23/33] generic dynamic per cpu refcounting Kent Overstreet
2013-04-02 16:27 ` Theodore Ts'o
2013-04-12 19:36 ` Kent Overstreet
2013-04-16 1:41 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 24/33] aio: percpu ioctx refcount Kent Overstreet
2013-04-02 16:28 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 25/33] aio: use xchg() instead of completion_lock Kent Overstreet
2013-04-02 16:35 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 26/33] aio: don't include aio.h in sched.h Kent Overstreet
2013-04-02 16:35 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 27/33] aio: kill ki_key Kent Overstreet
2013-04-02 16:36 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 28/33] aio: kill ki_retry Kent Overstreet
2013-04-02 18:46 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 29/33] block: Prep work for batch completion Kent Overstreet
2013-04-02 18:48 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 30/33] block, aio: batch completion for bios/kiocbs Kent Overstreet
2013-04-02 19:48 ` Theodore Ts'o
2013-04-10 21:59 ` Kent Overstreet
2013-04-02 19:53 ` Theodore Ts'o
2013-04-10 22:09 ` Kent Overstreet
2013-03-21 16:35 ` [PATCH 31/33] virtio-blk: convert to batch completion Kent Overstreet
2013-04-02 19:53 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 32/33] mtip32xx: " Kent Overstreet
2013-04-02 19:54 ` Theodore Ts'o
2013-03-21 16:35 ` [PATCH 33/33] aio: fix kioctx not being freed after cancellation at exit time Kent Overstreet
2013-04-02 21:35 ` Theodore Ts'o
2013-04-09 21:15 ` Kent Overstreet
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