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From: Alan Stern <stern@rowland.harvard.edu>
To: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	"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: Mon, 16 Jan 2017 12:09:20 -0500 (EST)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1701161207000.17898-100000@netrider.rowland.org> (raw)
In-Reply-To: <87eg03mf69.fsf@linux.intel.com>

On Mon, 16 Jan 2017, Felipe Balbi wrote:

> Sorry for the long delay, I finally have more information on this. All
> this time I was doing something that I never considered to matter: I've
> been running host and peripheral on the same machine. Now that I have
> tracepoints on xHCI as well, I could see that these 30 seconds of
> "nothing" is actuall full of xHCI activity and I can see that for the
> duration of these 30 seconds preempt depth on the CPU that (eventually)
> queues a request on dwc3, is always > 1 (sometimes 2, most of the time
> 1). My conclusion from that is that xHCI (or usbcore ?!?) locks the CPU
> and g_mass_storage is spinning for over 30 seconds at which point
> storage.ko (host side class driver) dequeues the request.
> 
> I'll see if I can capture a fresh trace with both xHCI and dwc3 with
> this happening, but probably not today (testing stuff for -rc).

Does anything change if the host and peripheral are separate machines?

Alan Stern

  reply	other threads:[~2017-01-16 17:09 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
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 [this message]
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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