linux-kernel - RE: 2.6.18.4: flush_workqueue calls mutex

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Date:	Fri, 15 Dec 2006 10:58:28 -0800
From:	"Chen, Kenneth W" <kenneth.w.chen@...el.com>
To:	"'Trond Myklebust'" <trond.myklebust@....uio.no>
Cc:	"'Andrew Morton'" <akpm@...l.org>, <linux-aio@...ck.org>,
	"'xb'" <xavier.bru@...l.net>, <linux-kernel@...r.kernel.org>,
	"'Zach Brown'" <zach.brown@...cle.com>
Subject: RE: 2.6.18.4: flush_workqueue calls mutex_lock in interruptenvironment

Trond Myklebust wrote on Friday, December 15, 2006 6:01 AM
> Oops. Missed the fact that you are removed the put_ioctx from
> aio_put_req, but the first sentence is still true. If you try to wake up
> wait_for_all_aios before you've changed the condition it is waiting for,
> then it may end up hanging forever.

The easy fix to that is to put wake_up in aio_complete inside the ctx spin
lock.

> Why not fix this by having the context freed via an RCU callback? That
> way you can protect the combined call to aio_put_req() +
> wake_up(ctx->wait) using a simple preempt_off/preempt_on, and all is
> good.

That has been suggested before on a different subject.  I will whip up
something.
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