From: Tejun Heo <tj@kernel.org>
To: Peter Hurley <peter@hurleysoftware.com>
Cc: laijs@cn.fujitsu.com, linux-kernel@vger.kernel.org,
Stefan Richter <stefanr@s5r6.in-berlin.de>,
linux1394-devel@lists.sourceforge.net,
Chris Boot <bootc@bootc.net>,
linux-scsi@vger.kernel.org, target-devel@vger.kernel.org
Subject: Re: [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK
Date: Sat, 22 Feb 2014 09:38:59 -0500 [thread overview]
Message-ID: <20140222143859.GD12830@htj.dyndns.org> (raw)
In-Reply-To: <5307E550.4040004@hurleysoftware.com>
Hey,
On Fri, Feb 21, 2014 at 06:46:24PM -0500, Peter Hurley wrote:
> It's a long story but the short version is that
> Documentation/memory-barriers.txt recently was overhauled to reflect
> what cpus actually do and what the different archs actually
> deliver.
>
> Turns out that unlock + lock is not guaranteed by all archs to be
> a full barrier. Thus the smb_mb__after_unlock_lock().
>
> This is now all spelled out in memory-barriers.txt under the
> sub-heading "IMPLICIT KERNEL MEMORY BARRIERS".
So, that one is for unlock/lock sequence, not smp_mb__after_unlock().
Urgh... kinda dislike adding smp_rmb() there as it's one of the
barriers which translate to something weighty on most, if not all,
archs.
Thanks.
--
tejun
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Peter Hurley <peter@hurleysoftware.com>
Cc: laijs@cn.fujitsu.com, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux1394-devel@lists.sourceforge.net,
target-devel@vger.kernel.org
Subject: Re: [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK
Date: Sat, 22 Feb 2014 09:38:59 -0500 [thread overview]
Message-ID: <20140222143859.GD12830@htj.dyndns.org> (raw)
In-Reply-To: <5307E550.4040004@hurleysoftware.com>
Hey,
On Fri, Feb 21, 2014 at 06:46:24PM -0500, Peter Hurley wrote:
> It's a long story but the short version is that
> Documentation/memory-barriers.txt recently was overhauled to reflect
> what cpus actually do and what the different archs actually
> deliver.
>
> Turns out that unlock + lock is not guaranteed by all archs to be
> a full barrier. Thus the smb_mb__after_unlock_lock().
>
> This is now all spelled out in memory-barriers.txt under the
> sub-heading "IMPLICIT KERNEL MEMORY BARRIERS".
So, that one is for unlock/lock sequence, not smp_mb__after_unlock().
Urgh... kinda dislike adding smp_rmb() there as it's one of the
barriers which translate to something weighty on most, if not all,
archs.
Thanks.
--
tejun
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next prev parent reply other threads:[~2014-02-22 14:39 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-20 20:44 [PATCHSET wq/for-3.15] workqueue: remove PREPARE_[DELAYED_]WORK() Tejun Heo
2014-02-20 20:44 ` [PATCH 1/9] wireless/rt2x00: don't use PREPARE_WORK in rt2800usb.c Tejun Heo
2014-03-07 15:26 ` Tejun Heo
2014-02-20 20:44 ` [PATCH 2/9] ps3-vuart: don't use PREPARE_WORK Tejun Heo
2014-02-20 20:44 ` Tejun Heo
2014-02-21 23:19 ` Geoff Levand
2014-02-21 23:19 ` Geoff Levand
2014-02-20 20:44 ` [PATCH 3/9] floppy: don't use PREPARE_[DELAYED_]WORK Tejun Heo
2014-02-21 9:37 ` Jiri Kosina
2014-02-20 20:44 ` [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK Tejun Heo
2014-02-20 20:44 ` Tejun Heo
2014-02-21 1:44 ` Peter Hurley
2014-02-21 1:59 ` Tejun Heo
2014-02-21 2:07 ` Peter Hurley
2014-02-21 2:07 ` Peter Hurley
2014-02-21 2:13 ` Tejun Heo
2014-02-21 5:13 ` Peter Hurley
2014-02-21 10:03 ` Tejun Heo
2014-02-21 12:51 ` Peter Hurley
2014-02-21 12:51 ` Peter Hurley
2014-02-21 13:06 ` Tejun Heo
2014-02-21 16:53 ` Peter Hurley
2014-02-21 16:57 ` Tejun Heo
2014-02-21 23:01 ` Peter Hurley
2014-02-21 23:18 ` Tejun Heo
2014-02-21 23:46 ` Peter Hurley
2014-02-22 14:38 ` Tejun Heo [this message]
2014-02-22 14:38 ` Tejun Heo
2014-02-22 14:48 ` Peter Hurley
2014-02-22 18:43 ` James Bottomley
2014-02-22 18:48 ` Peter Hurley
2014-02-22 18:48 ` Peter Hurley
2014-02-22 18:52 ` James Bottomley
2014-02-22 19:03 ` Peter Hurley
2014-02-22 19:03 ` Peter Hurley
2014-02-23 1:23 ` memory-barriers.txt again (was Re: [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK) Stefan Richter
2014-02-23 16:37 ` Paul E. McKenney
2014-02-23 16:37 ` Paul E. McKenney
2014-02-23 20:35 ` Peter Hurley
2014-02-23 23:50 ` Paul E. McKenney
2014-02-24 0:09 ` Peter Hurley
2014-02-24 16:26 ` Paul E. McKenney
2014-02-24 16:26 ` Paul E. McKenney
2014-02-24 0:32 ` Stefan Richter
2014-02-24 16:27 ` Paul E. McKenney
2014-02-23 20:05 ` [PATCH 4/9] firewire: don't use PREPARE_DELAYED_WORK James Bottomley
2014-02-23 22:32 ` Peter Hurley
2014-02-21 20:45 ` Stefan Richter
2014-02-21 20:45 ` Stefan Richter
2014-03-05 21:34 ` Stefan Richter
2014-03-07 15:18 ` Tejun Heo
2014-03-07 15:26 ` [PATCH UPDATED " Tejun Heo
2014-03-07 15:26 ` Tejun Heo
2014-02-20 20:44 ` [PATCH 5/9] usb: " Tejun Heo
2014-02-20 20:59 ` Greg Kroah-Hartman
2014-02-21 15:06 ` Alan Stern
2014-02-21 15:07 ` Tejun Heo
2014-02-22 14:59 ` [PATCH v2 " Tejun Heo
2014-02-22 15:14 ` Alan Stern
2014-02-22 15:20 ` Peter Hurley
2014-02-22 15:37 ` Tejun Heo
2014-02-22 23:03 ` Alan Stern
2014-02-23 4:29 ` Tejun Heo
2014-02-20 20:44 ` [PATCH 6/9] nvme: don't use PREPARE_WORK Tejun Heo
2014-02-20 20:44 ` Tejun Heo
2014-03-07 15:26 ` Tejun Heo
2014-03-07 15:26 ` Tejun Heo
2014-02-20 20:44 ` [PATCH 7/9] afs: " Tejun Heo
2014-03-07 15:27 ` Tejun Heo
2014-02-20 20:44 ` [PATCH 8/9] staging/fwserial: " Tejun Heo
2014-02-21 15:13 ` Peter Hurley
2014-02-20 20:44 ` [PATCH 9/9] workqueue: remove PREPARE_[DELAYED_]WORK() Tejun Heo
2014-03-07 15:27 ` Tejun Heo
2014-02-20 22:00 ` [PATCH 7/9] afs: don't use PREPARE_WORK David Howells
2014-02-20 22:46 ` Tejun Heo
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