Re: [PATCH] video4linux: Push down the BKL

Previous message: [thread] [date] [author]
Next message: [thread] [date] [author]

To: Mauro Carvalho Chehab <mchehab@...>

Cc: Alan Cox <alan@...>, <video4linux-list@...>, <linux-kernel@...>, Alan Cox <alan@...>

Subject: Re: [PATCH] video4linux: Push down the BKL

Date: Tuesday, May 27, 2008 - 11:41 am

On Tue, 27 May 2008 10:10:39 -0300
Mauro Carvalho Chehab <mchehab@infradead.org> wrote:

quoted text> What if we create 3 functions:
> 
> video_ioctl2_bkl()
> video_ioctl2_serialized()
> video_ioctl2_unlocked()
> 
> The first patch will point .ioctl_unlock to video_ioctl2_bkl. 
> 
> A next step would be to move the drivers to use the serialized one. 

So we're replacing the big kernel lock with the big v4l2 lock.  That
might help the situation, but you'd need to be sure to serialize
against other calls (open(), for example) which are also currently done
under the BKL.

quoted text> IMO, we need to create a multi-thread stress userspace tool for
> checking the locks at the ioctls. There are a few testing utils at
> mercurial tree, under v4l2-apps/test. This can be a starting point
> for this tool. Also, Brandon improved one of those tools to work with
> multithread.

I don't think that stress tools are the way to eliminate the BKL.
You'll never find all the problems that way.  There's really no way to
avoid the task of actually *looking* at each driver and ensuring that
it has its act together with regard to locking.

jon
--
unsubscribe noticeTo 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/

Previous message: [thread] [date] [author]
Next message: [thread] [date] [author]

Messages in current thread:

[PATCH] video4linux: Push down the BKL, Alan Cox, (Thu May 22, 5:37 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Mon May 26, 12:59 pm)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Mon May 26, 4:23 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Mon May 26, 5:10 pm)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Mon May 26, 6:01 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Tue May 27, 9:10 am)

Re: [PATCH] video4linux: Push down the BKL, Jonathan Corbet, (Tue May 27, 11:41 am)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Tue May 27, 12:31 pm)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Tue May 27, 2:14 pm)

Re: [PATCH] video4linux: Push down the BKL, Jonathan Corbet, (Tue May 27, 12:37 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Tue May 27, 2:59 pm)

Re: [PATCH] video4linux: Push down the BKL, Arjan van de Ven, (Tue May 27, 3:50 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Tue May 27, 4:24 pm)

Re: [PATCH] video4linux: Push down the BKL, Devin Heitmueller, (Tue May 27, 3:26 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Tue May 27, 5:00 pm)

Re: [PATCH] video4linux: Push down the BKL, Andy Walls, (Tue May 27, 7:48 pm)

Re: [PATCH] video4linux: Push down the BKL, Devin Heitmueller, (Tue May 27, 8:46 pm)

Re: [PATCH] video4linux: Push down the BKL, Hans Verkuil, (Wed May 28, 2:13 am)

Re: [PATCH] video4linux: Push down the BKL, Andy Walls, (Tue May 27, 10:37 pm)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Wed May 28, 4:34 am)

Re: [PATCH] video4linux: Push down the BKL, Devin Heitmueller, (Tue May 27, 10:47 pm)

Re: [PATCH] video4linux: Push down the BKL, Devin Heitmueller, (Tue May 27, 5:22 pm)

Re: [PATCH] video4linux: Push down the BKL, Mike Isely, (Sun May 25, 7:46 pm)

Re: [PATCH] video4linux: Push down the BKL, Hans Verkuil, (Fri May 23, 3:05 pm)

Re: [PATCH] video4linux: Push down the BKL , Jonathan Corbet, (Fri May 23, 9:56 am)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Fri May 23, 11:39 am)

Re: [PATCH] video4linux: Push down the BKL , Jonathan Corbet, (Fri May 23, 12:09 pm)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Fri May 23, 2:58 pm)

Re: [PATCH] video4linux: Push down the BKL, Andy Walls, (Thu May 22, 10:08 pm)

Re: [PATCH] video4linux: Push down the BKL, Alan Cox, (Fri May 23, 5:09 am)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Mon May 26, 12:34 pm)

Re: [PATCH] video4linux: Push down the BKL, Hans Verkuil, (Mon May 26, 12:46 pm)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Mon May 26, 5:14 pm)

Re: [PATCH] video4linux: Push down the BKL, Hans Verkuil, (Fri May 23, 2:16 am)

Re: [PATCH] video4linux: Push down the BKL, Mauro Carvalho Chehab, (Mon May 26, 12:39 pm)

Re: [PATCH] video4linux: Push down the BKL, Hans Verkuil, (Fri May 23, 2:28 am)


linux-kernel:
Benjamin Herrenschmidt	Re: [linux-pm] [PATCH] Remove process freezer from suspend to RAM pathway
Ulrich Drepper	Re: [patch 7/8] fdmap v2 - implement sys_socket2
Washington Odhiambo	Weird Problem with NAT - more details
Greg Kroah-Hartman	[PATCH 001/196] Chinese: Add the known_regression URI to the HOWTO
git:

linux-netdev:
Gerrit Renker	[PATCH 27/37] dccp: Integration of dynamic feature activation - part 2 (server side)
Frans Pop	svc: failed to register lockdv1 RPC service (errno 97).
Jarek Poplawski	[PATCH take 2] pkt_sched: Protect gen estimators under est_lock.
David Miller	Re: [GIT]: Networking
openbsd-misc:

Re: [PATCH] video4linux: Push down the BKL

Online users