Re: [PATCH] bttv: fix mutex use before init
From: Dave Young
Date: Tue Dec 14 2010 - 07:05:50 EST
On Mon, Dec 13, 2010 at 04:30:24PM -0800, Brandon Philips wrote:
> On 17:13 Sun 12 Dec 2010, Torsten Kaiser wrote:
> > * change &fh->cap.vb_lock in bttv_open() AND radio_open() to
> > &btv->init.cap.vb_lock
> > * add a mutex_init(&btv->init.cap.vb_lock) to the setup of init in bttv_probe()
>
> That seems like a reasonable suggestion. An openSUSE user submitted this
> bug to our tracker too. Here is the patch I am having him test.
>
> Would you mind testing it?
>
> From 456dc0ce36db523c4c0c8a269f4eec43a72de1dc Mon Sep 17 00:00:00 2001
> From: Brandon Philips <bphilips@xxxxxxx>
> Date: Mon, 13 Dec 2010 16:21:55 -0800
> Subject: [PATCH] bttv: fix locking for btv->init
>
> Fix locking for the btv->init by using btv->init.cap.vb_lock and in the
> process fix uninitialized deref introduced in c37db91fd0d.
Tested this patch, seems fine. But there's still possible deadlock, kernel hangs with lockdep warning, I think maybe it is another issue.
Could some v4l2 guys who have deep understand about bttv driver have a look at this issue?
[ 322.172772] bttv: driver version 0.9.18 loaded
[ 322.172781] bttv: using 8 buffers with 2080k (520 pages) each for capture
[ 322.173300] bttv: Bt8xx card found (0).
[ 322.174510] bttv 0000:03:01.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[ 322.174560] bttv0: Bt878 (rev 17) at 0000:03:01.0, irq: 17, latency: 64, mmio: 0xd0001000
[ 322.174679] bttv0: detected: Leadtek WinFast TV 2000 [card=34], PCI subsystem ID is 107d:6606
[ 322.174687] bttv0: using: Leadtek WinFast 2000/ WinFast 2000 XP [card=34,autodetected]
[ 322.175062] bttv0: gpio: en=00000000, out=00000000 in=003fbfff [init]
[ 322.178792] bttv0: tuner type=5
[ 322.254454] bttv0: audio absent, no audio device found!
[ 322.289946] tuner 1-0061: chip found @ 0xc2 (bt878 #0 [sw])
[ 322.290944] tuner-simple 1-0061: creating new instance
[ 322.290953] tuner-simple 1-0061: type set to 5 (Philips PAL_BG (FI1216 and compatibles))
[ 322.295830] bttv0: registered device video0
[ 322.300020] bttv0: registered device vbi0
[ 322.303216] bttv0: registered device radio0
[ 322.303636] bttv0: PLL: 28636363 => 35468950 .. ok
[ 322.334635] Registered IR keymap rc-winfast
[ 322.341201] input: bttv IR (card=34) as /devices/pci0000:00/0000:00:1e.0/0000:03:01.0/rc/rc0/input4
[ 322.357025] rc0: bttv IR (card=34) as /devices/pci0000:00/0000:00:1e.0/0000:03:01.0/rc/rc0
[ 382.342433] bttv0: PLL can sleep, using XTAL (28636363).
[ 382.816353] irq event stamp: 1078776
[ 382.816363] hardirqs last enabled at (1078775): [<c105604d>] debug_check_no_locks_freed+0x102/0x113
[ 382.816381]
[ 382.816384] =======================================================
[ 382.816389] [ INFO: possible circular locking dependency detected ]
[ 382.816394] 2.6.37-rc5-00062-g6313e3c-dirty #114
[ 382.816398] -------------------------------------------------------
[ 382.816403] kdetv/2109 is trying to acquire lock:
[ 382.816408] (&mm->mmap_sem){++++++}, at: [<c10b1bf5>] might_fault+0x47/0x81
[ 382.816422]
[ 382.816424] but task is already holding lock:
[ 382.816427] (&q->vb_lock){+.+.+.}, at: [<e00af2be>] videobuf_queue_lock+0x10/0x12 [videobuf_core]
[ 382.816442]
[ 382.816444] which lock already depends on the new lock.
[ 382.816446]
[ 382.816449]
[ 382.816450] the existing dependency chain (in reverse order) is:
[ 382.816455]
[ 382.816456] -> #1 (&q->vb_lock){+.+.+.}:
[ 382.816463] [<c10574dc>] lock_acquire+0xa1/0xc4
[ 382.816472] [<c14ef90d>] __mutex_lock_common+0x35/0x2dc
[ 382.816482] [<c14efc52>] mutex_lock_nested+0x30/0x38
[ 382.816489] [<e00af2be>] videobuf_queue_lock+0x10/0x12 [videobuf_core]
[ 382.816499] [<e00af339>] videobuf_mmap_mapper+0x69/0xc0 [videobuf_core]
[ 382.816509] [<e18aae49>] bttv_mmap+0x66/0x6d [bttv]
[ 382.816522] [<c140009a>] v4l2_mmap+0x5a/0x73
[ 382.816532] [<c10b7f0c>] mmap_region+0x24c/0x400
[ 382.816540] [<c10b82ef>] do_mmap_pgoff+0x22f/0x27f
[ 382.816547] [<c10b841c>] sys_mmap_pgoff+0xdd/0x119
[ 382.816560] [<c14f0d55>] syscall_call+0x7/0xb
[ 382.816569]
[ 382.816571] -> #0 (&mm->mmap_sem){++++++}:
[ 382.816577] [<c105718c>] __lock_acquire+0x9d7/0xc86
[ 382.816585] [<c10574dc>] lock_acquire+0xa1/0xc4
[ 382.816592] [<c10b1c12>] might_fault+0x64/0x81
[ 382.816599] [<c1297552>] copy_to_user+0x2c/0xfe
[ 382.816608] [<e00b0851>] videobuf_read_stream+0x17f/0x24c [videobuf_core]
[ 382.816619] [<e18ab05b>] bttv_read+0xcf/0xe9 [bttv]
[ 382.816633] [<c14002bb>] v4l2_read+0x63/0x7f
[ 382.816640] [<c10ce67e>] vfs_read+0x81/0xdb
[ 382.816649] [<c10ce771>] sys_read+0x3b/0x60
[ 382.816655] [<c14f0d55>] syscall_call+0x7/0xb
[ 382.816663]
[ 382.816665] other info that might help us debug this:
[ 382.816667]
[ 382.816671] 1 lock held by kdetv/2109:
[ 382.816675] #0: (&q->vb_lock){+.+.+.}, at: [<e00af2be>] videobuf_queue_lock+0x10/0x12 [videobuf_core]
[ 382.816688]
[ 382.816690] stack backtrace:
[ 382.816695] Pid: 2109, comm: kdetv Not tainted 2.6.37-rc5-00062-g6313e3c-dirty #114
[ 382.816700] Call Trace:
[ 382.816639] hardirqs last disabled at (1078776): [<c1002ea7>] common_interrupt+0x27/0x34
[ 382.816639] softirqs last enabled at (1078294): [<c1034a8b>] __do_softirq+0x17b/0x183
[ 382.816639] softirqs last disabled at (1078271): [<c1003ffb>] do_softirq+0x67/0xc0
[ 382.816738] [<c14ee80b>] ? printk+0x20/0x24
[ 382.816748] [<c1056480>] print_circular_bug+0x9c/0xa8
[ 382.816758] [<c105718c>] __lock_acquire+0x9d7/0xc86
[ 382.816769] [<c103a908>] ? __mod_timer+0x10c/0x117
[ 382.816779] [<c10574dc>] lock_acquire+0xa1/0xc4
[ 382.816788] [<c10b1bf5>] ? might_fault+0x47/0x81
[ 382.816798] [<c10b1c12>] might_fault+0x64/0x81
[ 382.816807] [<c10b1bf5>] ? might_fault+0x47/0x81
[ 382.816815] [<c1297552>] copy_to_user+0x2c/0xfe
[ 382.816828] [<e00b0851>] videobuf_read_stream+0x17f/0x24c [videobuf_core]
[ 382.816844] [<e18ab05b>] bttv_read+0xcf/0xe9 [bttv]
[ 382.816854] [<c14002bb>] v4l2_read+0x63/0x7f
[ 382.816865] [<c1400258>] ? v4l2_read+0x0/0x7f
[ 382.816874] [<c10ce67e>] vfs_read+0x81/0xdb
[ 382.816883] [<c10ce771>] sys_read+0x3b/0x60
[ 382.816893] [<c14f0d55>] syscall_call+0x7/0xb
[ 382.816902] [<c14f0000>] ? rt_mutex_trylock+0x2a/0x2d
>
> Signed-off-by: Brandon Philips <bphilips@xxxxxxx>
> ---
> drivers/media/video/bt8xx/bttv-driver.c | 24 +++++++++++++-----------
> 1 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/media/video/bt8xx/bttv-driver.c b/drivers/media/video/bt8xx/bttv-driver.c
> index a529619..e656424 100644
> --- a/drivers/media/video/bt8xx/bttv-driver.c
> +++ b/drivers/media/video/bt8xx/bttv-driver.c
> @@ -2391,16 +2391,11 @@ static int setup_window_lock(struct bttv_fh *fh, struct bttv *btv,
> fh->ov.field = win->field;
> fh->ov.setup_ok = 1;
>
> - /*
> - * FIXME: btv is protected by btv->lock mutex, while btv->init
> - * is protected by fh->cap.vb_lock. This seems to open the
> - * possibility for some race situations. Maybe the better would
> - * be to unify those locks or to use another way to store the
> - * init values that will be consumed by videobuf callbacks
> - */
> + mutex_lock(&btv->init.cap.vb_lock);
> btv->init.ov.w.width = win->w.width;
> btv->init.ov.w.height = win->w.height;
> btv->init.ov.field = win->field;
> + mutex_unlock(&btv->init.cap.vb_lock);
>
> /* update overlay if needed */
> retval = 0;
> @@ -2620,9 +2615,11 @@ static int bttv_s_fmt_vid_cap(struct file *file, void *priv,
> fh->cap.last = V4L2_FIELD_NONE;
> fh->width = f->fmt.pix.width;
> fh->height = f->fmt.pix.height;
> + mutex_lock(&btv->init.cap.vb_lock);
> btv->init.fmt = fmt;
> btv->init.width = f->fmt.pix.width;
> btv->init.height = f->fmt.pix.height;
> + mutex_unlock(&btv->init.cap.vb_lock);
> mutex_unlock(&fh->cap.vb_lock);
>
> return 0;
> @@ -2855,6 +2852,7 @@ static int bttv_s_fbuf(struct file *file, void *f,
>
> retval = 0;
> fh->ovfmt = fmt;
> + mutex_lock(&btv->init.cap.vb_lock);
> btv->init.ovfmt = fmt;
> if (fb->flags & V4L2_FBUF_FLAG_OVERLAY) {
> fh->ov.w.left = 0;
> @@ -2876,6 +2874,7 @@ static int bttv_s_fbuf(struct file *file, void *f,
> retval = bttv_switch_overlay(btv, fh, new);
> }
> }
> + mutex_unlock(&btv->init.cap.vb_lock);
> mutex_unlock(&fh->cap.vb_lock);
> return retval;
> }
> @@ -3141,6 +3140,7 @@ static int bttv_s_crop(struct file *file, void *f, struct v4l2_crop *crop)
> fh->do_crop = 1;
>
> mutex_lock(&fh->cap.vb_lock);
> + mutex_lock(&btv->init.cap.vb_lock);
>
> if (fh->width < c.min_scaled_width) {
> fh->width = c.min_scaled_width;
> @@ -3158,6 +3158,7 @@ static int bttv_s_crop(struct file *file, void *f, struct v4l2_crop *crop)
> btv->init.height = c.max_scaled_height;
> }
>
> + mutex_unlock(&btv->init.cap.vb_lock);
> mutex_unlock(&fh->cap.vb_lock);
>
> return 0;
> @@ -3302,9 +3303,9 @@ static int bttv_open(struct file *file)
> * Let's first copy btv->init at fh, holding cap.vb_lock, and then work
> * with the rest of init, holding btv->lock.
> */
> - mutex_lock(&fh->cap.vb_lock);
> + mutex_lock(&btv->init.cap.vb_lock);
> *fh = btv->init;
> - mutex_unlock(&fh->cap.vb_lock);
> + mutex_unlock(&btv->init.cap.vb_lock);
>
> fh->type = type;
> fh->ov.setup_ok = 0;
> @@ -3502,9 +3503,9 @@ static int radio_open(struct file *file)
> if (unlikely(!fh))
> return -ENOMEM;
> file->private_data = fh;
> - mutex_lock(&fh->cap.vb_lock);
> + mutex_lock(&btv->init.cap.vb_lock);
> *fh = btv->init;
> - mutex_unlock(&fh->cap.vb_lock);
> + mutex_unlock(&btv->init.cap.vb_lock);
>
> mutex_lock(&btv->lock);
> v4l2_prio_open(&btv->prio, &fh->prio);
> @@ -4489,6 +4490,7 @@ static int __devinit bttv_probe(struct pci_dev *dev,
> btv->opt_coring = coring;
>
> /* fill struct bttv with some useful defaults */
> + mutex_init(&btv->init.cap.vb_lock);
> btv->init.btv = btv;
> btv->init.ov.w.width = 320;
> btv->init.ov.w.height = 240;
> --
> 1.7.3.1
>
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