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From: Tejun Heo <tj@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Petr Mladek <pmladek@suse.cz>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Joe Lawrence <joe.lawrence@stratus.com>,
	Jiri Kosina <jkosina@suse.cz>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 4/4] usb: hub: rename khubd to hub_wq in documentation and comments
Date: Thu, 18 Sep 2014 06:22:38 +0900	[thread overview]
Message-ID: <20140917212238.GB15795@mtj.dyndns.org> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1409171333310.1579-100000@iolanthe.rowland.org>

Hello, Alan, Petr.

On Wed, Sep 17, 2014 at 01:36:26PM -0400, Alan Stern wrote:
> > -	/* If khubd ever becomes multithreaded, this will need a lock */
> > +	/* If hub_wq ever becomes multithreaded, this will need a lock */
> >  	if (udev->wusb) {
> >  		devnum = udev->portnum + 1;
> >  		BUG_ON(test_bit(devnum, bus->devmap.devicemap));
> 
> You probably didn't notice when changing this comment.  But in fact,
> workqueues _are_ multithreaded.  Therefore you need to add a lock to 
> this routine.

Haven't read the code but if this function is called from a single
work_struct, workqueue guarantees that there's only single thread of
execution at any given time.  A work item is never executed
concurrently no matter what.

Thanks.

-- 
tejun

  reply	other threads:[~2014-09-17 21:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-17 15:19 [PATCH v2 0/4] usb: hub: convert khubd into workqueue Petr Mladek
2014-09-17 15:19 ` [PATCH v2 1/4] " Petr Mladek
2014-09-17 17:31   ` Alan Stern
2014-09-17 15:19 ` [PATCH v2 2/4] usb: hub: remove obsolete while cycle in hub_event() Petr Mladek
2014-09-17 17:33   ` Alan Stern
2014-09-17 15:19 ` [PATCH v2 3/4] usb: hub: rename usb_kick_khubd() to usb_kick_hub_wq() Petr Mladek
2014-09-17 15:19 ` [PATCH v2 4/4] usb: hub: rename khubd to hub_wq in documentation and comments Petr Mladek
2014-09-17 17:36   ` Alan Stern
2014-09-17 21:22     ` Tejun Heo [this message]
2014-09-18 14:24       ` Alan Stern
2014-09-18 16:15         ` Petr Mládek
2014-09-18 16:31           ` Tejun Heo
2014-09-18 17:21           ` Alan Stern

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