From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: mc@linux.vnet.ibm.com, Stephen Boyd <sboyd@codeaurora.org>,
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: Tue, 20 Dec 2011 14:06:28 +0000 [thread overview]
Message-ID: <20111220140628.GD23916@ZenIV.linux.org.uk> (raw)
In-Reply-To: <4EF084A4.3000106@linux.vnet.ibm.com>
On Tue, Dec 20, 2011 at 06:20:44PM +0530, Srivatsa S. Bhat wrote:
> > Hey, actually there is a simple solution: just nip it (or rather delay it)
> > in the bud ;) That is, we watch out for CPU_UP_PREPARE event and lock it
> > up there itself using our spinlock.. that way, that cpu will not come up
> > until we are done executing br_write_unlock(). In fact, we can even fail
> > the onlining of that cpu by returning appropriate value from our callback,
> > but that would be too harsh.. so we can settle for delaying the cpu online
Eeeek... Are you serious about leaving a spinlock grabbed by notifier
callback and not released until another callback call? That would be one
hell of a constraint on what these notifiers can do - _nothing_ between
these calls (including other notifier callbacks, etc.) would be allowed
to block.
That sounds extremely brittle...
next prev parent reply other threads:[~2011-12-20 14:06 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
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 [this message]
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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