From owner-freebsd-current@FreeBSD.ORG Wed Dec 21 18:27:00 2011 Return-Path: Delivered-To: freebsd-current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 15399106566C; Wed, 21 Dec 2011 18:27:00 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140]) by mx1.freebsd.org (Postfix) with ESMTP id 2E2278FC0C; Wed, 21 Dec 2011 18:26:58 +0000 (UTC) Received: from porto.starpoint.kiev.ua (porto-e.starpoint.kiev.ua [212.40.38.100]) by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id UAA26655; Wed, 21 Dec 2011 20:26:54 +0200 (EET) (envelope-from avg@FreeBSD.org) Received: from localhost ([127.0.0.1]) by porto.starpoint.kiev.ua with esmtp (Exim 4.34 (FreeBSD)) id 1RdQsP-000MrG-W6; Wed, 21 Dec 2011 20:26:54 +0200 Message-ID: <4EF224EC.9050101@FreeBSD.org> Date: Wed, 21 Dec 2011 20:26:52 +0200 From: Andriy Gapon User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:8.0) Gecko/20111206 Thunderbird/8.0 MIME-Version: 1.0 To: Hans Petter Selasky References: <4EEF2B11.6080802@FreeBSD.org> <4EF07EB0.9000209@FreeBSD.org> <4EF1C32D.3070107@FreeBSD.org> <201112211738.36126.hselasky@c2i.net> In-Reply-To: <201112211738.36126.hselasky@c2i.net> X-Enigmail-Version: undefined Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: FreeBSD current , "freebsd-usb@FreeBSD.org" Subject: Re: a few usb issues related to edge cases X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Dec 2011 18:27:00 -0000 on 21/12/2011 18:38 Hans Petter Selasky said the following: > On Wednesday 21 December 2011 12:29:49 Andriy Gapon wrote: >> on 20/12/2011 14:25 Andriy Gapon said the following: >>> I just wanted to draw your attention to the fact that obtaining any locks >>> in the kdb context (or USB polling code in general, even) is not a good >>> idea. Chances of getting into trouble on those locks are probably quite >>> moderate or even low, but they do exist. I am not sure if you are >>> getting any bug reports about such troubles :-) Regular users probably >>> do not use kdb too often and a panic for them is just a "crash", so they >>> likely do not expect anything usable/debuggable after that :-) >> >> Looking some more at the code I just got myself confused as to how the >> dumping to a umass device could work when the scheduler is stopped. >> It seems that the umass_command_start -> usbd_transfer_start -> >> usbd_callback_ss_done_defer functions would always put a transfer request >> onto a queue and try to wake up a thread to process that queue and the >> request. But that's obviously not going to work when the other thread is >> not going to be run. Have I missed a code path that leads directly to the >> controller in this context? Thank you for your help. > > Hi, > > Those threads should be polled when calling usbd_transfer_poll(). I.E. the > wakeup should be stubbed in the !scheduler_running case. Ah, that's what I missed! -- Andriy Gapon