Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754671Ab1DBOKJ (ORCPT ); Sat, 2 Apr 2011 10:10:09 -0400 Received: from lo.gmane.org ([80.91.229.12]:48282 "EHLO lo.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754170Ab1DBOKH (ORCPT ); Sat, 2 Apr 2011 10:10:07 -0400 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Andreas Huber Subject: Re: [RFC/PATCH 0/3] locking fixes for cx88 Date: Sat, 2 Apr 2011 14:05:30 +0000 (UTC) Message-ID: References: <20110327150610.4029.95961.reportbug@xen.corax.at> <20110327152810.GA32106@elie> <20110402093856.GA17015@elie> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: sea.gmane.org User-Agent: Loom/3.14 (http://gmane.org/) X-Loom-IP: 84.114.185.220 (Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2382 Lines: 67 Jonathan Nieder gmail.com> writes: > > Hi, > > Huber Andreas wrote[1]: > > > Processes that try to open a cx88-blackbird driven MPEG device will hang up. > > Here's a possible fix based on a patch by Ben Hutchings and > corrections from Andi Huber. Warning: probably full of mistakes (my > fault) since I'm not familiar with any of this stuff. Untested. > Review and testing would be welcome. > > Ben Hutchings (2): > [media] cx88: fix locking of sub-driver operations > [media] cx88: use a mutex to protect cx8802_devlist > > Jonathan Nieder (1): > [media] cx88: protect per-device driver list with device lock > > drivers/media/video/cx88/cx88-blackbird.c | 3 +- > drivers/media/video/cx88/cx88-dvb.c | 2 + > drivers/media/video/cx88/cx88-mpeg.c | 35 +++++++++++++++++++--------- > drivers/media/video/cx88/cx88.h | 10 +++++++- > 4 files changed, 37 insertions(+), 13 deletions(-) > There is an unrelated issue!!! The driver's active_ref count may become negative which leads to unpredictable behavior. (MPEG video device inaccessible, etc ...) Here's a possible fix ... diff -Nur a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c --- a/drivers/media/video/cx88/cx88-mpeg.c 2011-04-02 14:34:21.456569849 +0200 +++ b/drivers/media/video/cx88/cx88-mpeg.c 2011-04-02 14:32:55.467038000 +0200 @@ -642,12 +642,16 @@ { struct cx88_core *core = drv->core; + mpeg_dbg(1,"%s active driver references before release attempt: %d\n",core->name,core->active_ref); + if (drv->advise_release && --core->active_ref == 0) { drv->advise_release(drv); core->active_type_id = CX88_BOARD_NONE; mpeg_dbg(1,"%s() Post release GPIO=%x\n", __func__, cx_read(MO_GP0_IO)); } + + if(core->active_ref<0) core->active_ref=0; // prevent us from getting negative ref counts! return 0; } I can confirm that Johnathan's patchset plus applying this fix works! Tests done on amd64 hardware with 2 Hauppauge HVR1300 TV cards: Both were independently able to tune channels and stream encoded video through their MPEG encoder devices. Andi. -- 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/