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From: Peter Zijlstra <peterz@infradead.org>
To: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@redhat.com>,
	USB list <linux-usb@vger.kernel.org>,
	Kernel development list <linux-kernel@vger.kernel.org>,
	Will Deacon <will.deacon@arm.com>
Subject: Re: Memory barrier needed with wake_up_process()?
Date: Tue, 6 Sep 2016 13:49:37 +0200	[thread overview]
Message-ID: <20160906114937.GM10153@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <87a8flmexg.fsf@linux.intel.com>

On Tue, Sep 06, 2016 at 02:43:39PM +0300, Felipe Balbi wrote:

> > Could you confirm that bulk_{in,out}_complete() work on different
> > usb_request structures, and they can not, at any time, get called on the
> > _same_ request?
> 
> usb_requests are allocated for a specific endpoint and USB Device
> Controller (UDC) drivers refuse to queue requests allocated for epX to
> epY, so this really can never happen.

Good, thanks!

> My fear now, however, is that changing smp_[rw]mb() to smp_mb() just
> adds extra overhead which makes the problem much, much less likely to
> happen. Does that sound plausible to you?

I did consider that, but I've not sufficiently grokked the code to rule
out actual fail. So let me stare at this a bit more.

  reply	other threads:[~2016-09-06 11:49 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-02 18:10 Memory barrier needed with wake_up_process()? Alan Stern
2016-09-02 18:47 ` Paul E. McKenney
2016-09-02 20:29   ` Alan Stern
2016-09-03  9:07     ` Paul E. McKenney
2016-09-03 12:31     ` Peter Zijlstra
2016-09-03 14:26       ` Alan Stern
2016-09-03 14:49         ` Alan Stern
2016-09-05  8:33           ` Peter Zijlstra
2016-09-05 15:29             ` Alan Stern
2016-09-06 11:36               ` Peter Zijlstra
2016-09-06 11:43                 ` Felipe Balbi
2016-09-06 11:49                   ` Peter Zijlstra [this message]
2016-09-06 12:20                     ` Peter Zijlstra
2016-09-06 14:46                       ` Alan Stern
2016-09-06 15:05                         ` Peter Zijlstra
2016-09-07 10:12                         ` Felipe Balbi
2016-09-09 10:36                           ` Felipe Balbi
2016-09-09 16:12                             ` Alan Stern
2016-09-19 11:11                               ` Felipe Balbi
2016-09-19 17:35                                 ` Alan Stern
2016-09-20 10:12                                   ` Felipe Balbi
2016-09-20 12:53                                     ` Felipe Balbi
2016-09-20 14:40                                     ` Alan Stern
2017-01-16 11:12                                       ` Felipe Balbi
2017-01-16 17:09                                         ` Alan Stern
2017-01-16 19:04                                           ` Felipe Balbi
2017-01-16 19:19                                             ` Felipe Balbi
2016-09-02 19:18 ` Peter Zijlstra
2016-09-02 20:16   ` Alan Stern
2016-09-02 22:14     ` Peter Zijlstra
2016-09-02 22:16       ` Peter Zijlstra
2016-09-05  9:43         ` Will Deacon
2016-09-06 11:10           ` Peter Zijlstra
2016-09-02 22:16     ` Peter Zijlstra
2016-09-03  6:58       ` Felipe Balbi
2016-09-03 12:19         ` Peter Zijlstra
2016-09-03 13:51           ` Felipe Balbi
2016-09-05  8:09             ` Peter Zijlstra
2016-09-03 14:16           ` Alan Stern
2016-09-05  8:08             ` Peter Zijlstra
2016-09-05 14:33               ` Alan Stern

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