Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263516AbTEMV4o (ORCPT ); Tue, 13 May 2003 17:56:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263521AbTEMV4o (ORCPT ); Tue, 13 May 2003 17:56:44 -0400 Received: from ida.rowland.org ([192.131.102.52]:9220 "HELO ida.rowland.org") by vger.kernel.org with SMTP id S263516AbTEMV4n (ORCPT ); Tue, 13 May 2003 17:56:43 -0400 Date: Tue, 13 May 2003 18:09:30 -0400 (EDT) From: Alan Stern X-X-Sender: stern@ida.rowland.org To: Helge Hafting cc: Greg KH , Paul Fulghum , Andrew Morton , "linux-kernel@vger.kernel.org" , Arnd Bergmann , Subject: Re: 2.5.69 Interrupt Latency In-Reply-To: <20030513214830.GA685@hh.idb.hist.no> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1338 Lines: 27 On Tue, 13 May 2003, Helge Hafting wrote: > On Tue, May 13, 2003 at 05:35:47PM -0400, Alan Stern wrote: > > My take is that wakeup_hc() is getting called whenever some stray signal > > causes the device to generate an interrupt, and then a little while later > > the stall timer routine calls suspend_hc() since nothing is active. The > > interrupts are probably indistinguishable from what you would get if a new > > device really had just been attached to the bus. > > > Could this also happen if the USB interrupt is shared? > The other device interrupts, and the kernel calls into > usb interrupt routine just in case USB has some data too? Yes, it certainly could. The other part of the problem, which I failed to mention, is that the Resume-Detect bit in the USB controller's status register is set. wakeup_hc() gets called only if that bit is set, and the bit is supposed to be set only if some device attached to the USB bus has requested a wakeup (also known as "resume"). If there's nothing on the bus, the controller shouldn't indicate that a resume was detected. Alan Stern - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/