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.
next prev parent 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 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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