From: Andrew Morton <akpm@linux-foundation.org>
To: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
arjan@linux.intel.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Christian Kujau <lists@nerdbynature.de>,
Cong Wang <xiyou.wangcong@gmail.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH RESEND] Fix a dead loop in async_synchronize_full()
Date: Wed, 11 Jul 2012 15:42:32 -0700 [thread overview]
Message-ID: <20120711154232.165cbca9.akpm@linux-foundation.org> (raw)
In-Reply-To: <1341817465.4579.5.camel@ThinkPad-T420>
On Mon, 09 Jul 2012 15:04:25 +0800
Li Zhong <zhong@linux.vnet.ibm.com> wrote:
> This patch tries to fix a dead loop in async_synchronize_full(), which
> could be seen when preemption is disabled on a single cpu machine.
>
> void async_synchronize_full(void)
> {
> do {
> async_synchronize_cookie(next_cookie);
> } while (!list_empty(&async_running) || !
> list_empty(&async_pending));
> }
>
> async_synchronize_cookie() calls async_synchronize_cookie_domain() with
> &async_running as the default domain to synchronize.
>
> However, there might be some works in the async_pending list from other
> domains. On a single cpu system, without preemption, there is no chance
> for the other works to finish, so async_synchronize_full() enters a dead
> loop.
>
> It seems async_synchronize_full() wants to synchronize all entries in
> all running lists(domains), so maybe we could just check the entry_count
> to know whether all works are finished.
>
> Currently, async_synchronize_cookie_domain() expects a non-NULL running
> list ( if NULL, there would be NULL pointer dereference ), so maybe a
> NULL pointer could be used as an indication for the functions to
> synchronize all works in all domains.
The patch is fairly wordwrapped - please fix up your email client.
More seriously, it does not apply to linux-next due to some fairly
significant changes which have been sitting in Dan's tree since May.
What's going on?
next prev parent reply other threads:[~2012-07-11 22:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-09 7:04 [PATCH RESEND] Fix a dead loop in async_synchronize_full() Li Zhong
2012-07-11 22:42 ` Andrew Morton [this message]
2012-07-11 22:50 ` Dan Williams
2012-07-12 9:56 ` Li Zhong
2012-07-12 16:41 ` Dan Williams
2012-07-16 18:32 ` Christian Kujau
2012-07-16 23:01 ` Dan Williams
2012-07-17 1:57 ` Paul E. McKenney
2012-07-17 2:42 ` Li Zhong
2012-07-12 2:49 ` Li Zhong
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