linux-kernel - RE: [patch] aio: fix buggy put_ioctx call in aio

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Date:	Thu, 21 Dec 2006 09:01:28 -0800
From:	"Chen, Kenneth W" <kenneth.w.chen@...el.com>
To:	<jmoyer@...hat.com>
Cc:	"'Andrew Morton'" <akpm@...l.org>, <linux-aio@...ck.org>,
	"'Trond Myklebust'" <trond.myklebust@....uio.no>,
	"'xb'" <xavier.bru@...l.net>,
	"'Zach Brown'" <zach.brown@...cle.com>,
	<linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ibm.com>
Subject: RE: [patch] aio: fix buggy put_ioctx call in aio_complete

jmoyer@...hat.com wrote on Thursday, December 21, 2006 8:56 AM
> kenneth.w.chen> I think I'm going to abandon this whole synchronize thing
> kenneth.w.chen> and going to put the wake up call inside ioctx_lock spin
> kenneth.w.chen> lock along with the other patch you mentioned above in the
> kenneth.w.chen> waiter path.  On top of that, I have another patch attempts
> kenneth.w.chen> to perform wake-up only when the waiter can truly proceed
> kenneth.w.chen> in aio_read_evt so dribbling I/O completion doesn't
> kenneth.w.chen> inefficiently waking up waiter too frequently and only to
> kenneth.w.chen> have waiter put back to sleep again. I will dig that up and
> kenneth.w.chen> experiment.
> 
> In the mean time, can't we simply take the context lock in
> wait_for_all_aios?  Unless I missed something, I think that will address
> the reference count problem.

Take ioctx_lock is one part, the other part is to move

	spin_unlock_irqrestore(&ctx->ctx_lock, flags);

in aio_complete all the way down to the end of the function, after wakeup
and put_ioctx.  But then the ref counting on ioctx in aio_complete path is
Meaningless, which is the thing I'm trying to remove.

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