From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>,
mc@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, Nick Piggin <npiggin@kernel.dk>,
david@fromorbit.com,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
Maciej Rutecki <maciej.rutecki@gmail.com>
Subject: Re: [PATCH] VFS: br_write_lock locks on possible CPUs other than online CPUs
Date: Mon, 19 Dec 2011 20:52:51 +0000 [thread overview]
Message-ID: <20111219205251.GK2203@ZenIV.linux.org.uk> (raw)
In-Reply-To: <4EEF9D4E.1000008@linux.vnet.ibm.com>
On Tue, Dec 20, 2011 at 01:53:42AM +0530, Srivatsa S. Bhat wrote:
> If this new definition of our requirement is acceptable (correct me if I am
> wrong), then we can do something like the following patch, while still
> retaining br locks as non-blocking.
>
> We make a copy of the current cpu_online_mask, and lock the per-cpu locks of
> all those cpus. Then while unlocking, we unlock the per-cpu locks of these cpus
> (by using that temporary copy of cpu_online_mask we created earlier), without
> caring about the cpus actually online at that moment.
> IOW, we do lock-unlock on the same set of cpus, and that too, without missing
> the complete lock-unlock sequence in any of them. Guaranteed.
And what's to stop a process on a newly added CPU from _not_
spinning in br_read_lock(), even though br_write_unlock() hadn't been
done yet?
next prev parent reply other threads:[~2011-12-19 20:52 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-19 3:36 [PATCH] VFS: br_write_lock locks on possible CPUs other than online CPUs mengcong
2011-12-19 4:11 ` Al Viro
2011-12-19 5:00 ` Dave Chinner
2011-12-19 6:07 ` mengcong
2011-12-19 7:31 ` Srivatsa S. Bhat
2011-12-19 9:12 ` Stephen Boyd
2011-12-19 11:03 ` Srivatsa S. Bhat
2011-12-19 12:11 ` Al Viro
2011-12-19 20:23 ` Srivatsa S. Bhat
2011-12-19 20:52 ` Al Viro [this message]
2011-12-20 4:56 ` Srivatsa S. Bhat
2011-12-20 6:27 ` Al Viro
2011-12-20 7:28 ` Srivatsa S. Bhat
2011-12-20 9:37 ` mengcong
2011-12-20 10:36 ` Srivatsa S. Bhat
2011-12-20 11:08 ` Srivatsa S. Bhat
2011-12-20 12:50 ` Srivatsa S. Bhat
2011-12-20 14:06 ` Al Viro
2011-12-20 14:35 ` Srivatsa S. Bhat
2011-12-20 17:59 ` Al Viro
2011-12-20 19:12 ` Srivatsa S. Bhat
2011-12-20 19:58 ` Al Viro
2011-12-20 22:27 ` Dave Chinner
2011-12-20 23:31 ` Al Viro
2011-12-21 21:15 ` Srivatsa S. Bhat
2011-12-21 22:02 ` Al Viro
2011-12-21 22:12 ` Andrew Morton
2011-12-22 7:02 ` Al Viro
2011-12-22 7:20 ` Andrew Morton
2011-12-22 8:08 ` Al Viro
2011-12-22 8:17 ` Andi Kleen
2011-12-22 8:39 ` Al Viro
2011-12-22 8:22 ` Andi Kleen
2011-12-20 7:30 ` mengcong
2011-12-20 7:37 ` Srivatsa S. Bhat
2011-12-19 23:56 ` Dave Chinner
2011-12-20 4:05 ` Al Viro
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