netdev - Re: [PATCH net-next v5] rhashtable: Fix race in rhashtable_destroy() and use regular work

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Date:	Fri, 16 Jan 2015 01:19:08 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ying.xue@...driver.com
Cc:	tgraf@...g.ch, sergei.shtylyov@...entembedded.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5] rhashtable: Fix race in
 rhashtable_destroy() and use regular work_struct

From: Ying Xue <ying.xue@...driver.com>
Date: Fri, 16 Jan 2015 11:13:09 +0800

> When we put our declared work task in the global workqueue with
> schedule_delayed_work(), its delay parameter is always zero.
> Therefore, we should define a regular work in rhashtable structure
> instead of a delayed work.
> 
> By the way, we add a condition to check whether resizing functions
> are NULL before cancelling the work, avoiding to cancel an
> uninitialized work.
> 
> Lastly, while we wait for all work items we submitted before to run
> to completion with cancel_delayed_work(), ht->mutex has been taken in
> rhashtable_destroy(). Moreover, cancel_delayed_work() doesn't return
> until all work items are accomplished, and when work items are
> scheduled, the work's function - rht_deferred_worker() will be called.
> However, as rht_deferred_worker() also needs to acquire the lock,
> deadlock might happen at the moment as the lock is already held before.
> So if the cancel work function is moved out of the lock covered scope,
> this will avoid the deadlock.
> 
> Fixes: 97defe1 ("rhashtable: Per bucket locks & deferred expansion/shrinking")
> Signed-off-by: Ying Xue <ying.xue@...driver.com>
> Cc: Thomas Graf <tgraf@...g.ch>
> Acked-by: Thomas Graf <tgraf@...g.ch>

Applied, thanks.
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