Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753404Ab1EAJ3v (ORCPT ); Sun, 1 May 2011 05:29:51 -0400 Received: from mail-iw0-f174.google.com ([209.85.214.174]:56519 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753185Ab1EAJ3l (ORCPT ); Sun, 1 May 2011 05:29:41 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=TuPuZ+EZryMDnlL2SjcQpLD6I1TJ2wS6+ILM6X8CdMj0sxmeNN69NMi49uP67B0Zh1 VHorjfq7l/jKhx/TPOUksJGnV9UrLFneZxyBASFc+VrquXsCqiNLtqTPphlFQUyFEXWX reEMlxunqfgz6KqfvBxdkd7IpMwidjIdYGZtk= Date: Sun, 1 May 2011 04:29:37 -0500 From: Jonathan Nieder To: linux-media@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Mauro Carvalho Chehab , Dan Carpenter , Hans Verkuil , Andi Huber , Marlon de Boer , Damien Churchill Subject: [PATCH 2/7] [media] cx88: fix locking of sub-driver operations Message-ID: <20110501092937.GB18380@elie> References: <20110501091710.GA18263@elie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110501091710.GA18263@elie> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4067 Lines: 120 The BKL conversion of this driver seems to have gone wrong. Loading the cx88-blackbird driver deadlocks. The cause: mpeg_ops::open in the cx2388x blackbird driver acquires the device lock and calls the sub-driver's request_acquire, which tries to acquire the lock again. Fix it by clarifying the semantics of request_acquire, request_release, advise_acquire, and advise_release: now all will rely on the caller to acquire the device lock. Based on work by Ben Hutchings . Reported-by: Andi Huber Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=31962 Tested-by: Andi Huber Tested-by: Marlon de Boer Cc: stable@kernel.org Signed-off-by: Jonathan Nieder --- drivers/media/video/cx88/cx88-blackbird.c | 4 ++-- drivers/media/video/cx88/cx88-dvb.c | 3 +-- drivers/media/video/cx88/cx88-mpeg.c | 4 ---- drivers/media/video/cx88/cx88.h | 3 ++- 4 files changed, 5 insertions(+), 9 deletions(-) diff --git a/drivers/media/video/cx88/cx88-blackbird.c b/drivers/media/video/cx88/cx88-blackbird.c index b93fbd3..a6f7d53 100644 --- a/drivers/media/video/cx88/cx88-blackbird.c +++ b/drivers/media/video/cx88/cx88-blackbird.c @@ -1125,13 +1125,13 @@ static int mpeg_release(struct file *file) /* Make sure we release the hardware */ drv = cx8802_get_driver(dev, CX88_MPEG_BLACKBIRD); - mutex_unlock(&dev->core->lock); - if (drv) drv->request_release(drv); atomic_dec(&dev->core->mpeg_users); + mutex_unlock(&dev->core->lock); + return 0; } diff --git a/drivers/media/video/cx88/cx88-dvb.c b/drivers/media/video/cx88/cx88-dvb.c index 88a1507..5eccd02 100644 --- a/drivers/media/video/cx88/cx88-dvb.c +++ b/drivers/media/video/cx88/cx88-dvb.c @@ -134,8 +134,6 @@ static int cx88_dvb_bus_ctrl(struct dvb_frontend* fe, int acquire) mutex_lock(&dev->core->lock); drv = cx8802_get_driver(dev, CX88_MPEG_DVB); - mutex_unlock(&dev->core->lock); - if (drv) { if (acquire){ dev->frontends.active_fe_id = fe_id; @@ -145,6 +143,7 @@ static int cx88_dvb_bus_ctrl(struct dvb_frontend* fe, int acquire) dev->frontends.active_fe_id = 0; } } + mutex_unlock(&dev->core->lock); return ret; } diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c index 918172b..9147c16 100644 --- a/drivers/media/video/cx88/cx88-mpeg.c +++ b/drivers/media/video/cx88/cx88-mpeg.c @@ -624,13 +624,11 @@ static int cx8802_request_acquire(struct cx8802_driver *drv) if (drv->advise_acquire) { - mutex_lock(&drv->core->lock); core->active_ref++; if (core->active_type_id == CX88_BOARD_NONE) { core->active_type_id = drv->type_id; drv->advise_acquire(drv); } - mutex_unlock(&drv->core->lock); mpeg_dbg(1,"%s() Post acquire GPIO=%x\n", __func__, cx_read(MO_GP0_IO)); } @@ -643,14 +641,12 @@ static int cx8802_request_release(struct cx8802_driver *drv) { struct cx88_core *core = drv->core; - mutex_lock(&drv->core->lock); 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)); } - mutex_unlock(&drv->core->lock); return 0; } diff --git a/drivers/media/video/cx88/cx88.h b/drivers/media/video/cx88/cx88.h index 6ff34c7..e912919 100644 --- a/drivers/media/video/cx88/cx88.h +++ b/drivers/media/video/cx88/cx88.h @@ -500,7 +500,8 @@ struct cx8802_driver { /* Caller must _not_ hold core->lock */ int (*probe)(struct cx8802_driver *drv); - /* Caller must hold core->lock */ + /* Callers to the following functions must hold core->lock */ + int (*remove)(struct cx8802_driver *drv); /* MPEG 8802 -> mini driver - Access for hardware control */ -- 1.7.5 -- 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/