From: Chris Mason <chris.mason@oracle.com>
To: Sage Weil <sage@newdream.net>
Cc: liubo <liubo2009@cn.fujitsu.com>,
Linux Btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH 1/6] Btrfs: fix deadlock in btrfs_commit_transaction
Date: Tue, 26 Oct 2010 13:06:15 -0400 [thread overview]
Message-ID: <20101026170615.GE13254@think> (raw)
In-Reply-To: <Pine.LNX.4.64.1010260931310.7660@cobra.newdream.net>
On Tue, Oct 26, 2010 at 09:36:26AM -0700, Sage Weil wrote:
> On Tue, 26 Oct 2010, liubo wrote:
> >
> > Since wake_up() itself provides a implied wmb, and a wq active check,
> > it is better to drop "if (wq)" in __btrfs_end_transaction().
>
> I see. It could also be
>
> smb_mb();
> if (wq)
> wake_up();
>
> but just calling wake_up() unconditionally is simpler, and fewer barriers
> in the wake_up case. I'm not attached to the if (wq); I just kept it
> because it was there already.
wake_up() provides an implied barrier because it takes the lock. I
usually do the smp_mb() + if (wq) dance when I'm working on a relatively
hot waitqueue.
-chris
next prev parent reply other threads:[~2010-10-26 17:06 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-25 19:07 [PATCH 0/6] Btrfs commit fixes, async subvol operations Sage Weil
2010-10-25 19:07 ` [PATCH 1/6] Btrfs: fix deadlock in btrfs_commit_transaction Sage Weil
2010-10-25 19:07 ` [PATCH 2/6] Btrfs: async transaction commit Sage Weil
2010-10-25 19:07 ` [PATCH 3/6] Btrfs: add START_SYNC, WAIT_SYNC ioctls Sage Weil
2010-10-25 19:07 ` [PATCH 4/6] Btrfs: add SNAP_CREATE_ASYNC ioctl Sage Weil
2010-10-25 19:07 ` [PATCH 5/6] Btrfs: make SNAP_DESTROY async Sage Weil
2010-10-25 19:07 ` [PATCH 6/6] Btrfs: allow subvol deletion by owner Sage Weil
2010-10-26 6:46 ` [PATCH 1/6] Btrfs: fix deadlock in btrfs_commit_transaction liubo
2010-10-26 16:36 ` Sage Weil
2010-10-26 17:06 ` Chris Mason [this message]
2010-10-27 0:41 ` liubo
2010-10-25 19:29 ` [PATCH 0/6] Btrfs commit fixes, async subvol operations Chris Mason
2010-10-25 19:41 ` Sage Weil
2010-10-25 19:58 ` Chris Mason
2010-10-25 21:27 ` Sage Weil
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