Hi Hans
On 17.01.2014 12:04, Hans Verkuil wrote:
Hi Antti,
Is this still needed after this commit was merged?
http://git.linuxtv.org/media_tree.git/commit/b18a8ff29d80b132018d33479e86ab8ecaee6b46
It didn't fix the problem.
I could reproduce that issue easily using vivi and Cheese (webcam app).
1) Compile Kernel with lockdep debug. For me these seems to be enabled:
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_LOCKDEP=y
CONFIG_DEBUG_LOCKDEP=y
2) Load virtual video driver (vivi)
# modprobe vivi
3) Start Cheese
$ cheese
Lockdep error appears to system log just after Cheese is started. I
think it is related to mmap.
regards
Antti
tammi 17 17:07:38 localhost.localdomain kernel: media: Linux media
interface: v0.10
tammi 17 17:07:38 localhost.localdomain kernel: Linux video capture
interface: v2.00
tammi 17 17:07:38 localhost.localdomain kernel: vivi-000: V4L2 device
registered as video0
tammi 17 17:07:38 localhost.localdomain kernel: Video Technology
Magazine Virtual Video Capture Board ver 0.8.1 successfully loaded.
tammi 17 17:07:50 localhost.localdomain /etc/gdm/Xsession[1521]: Window
manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a
timestamp of 0 for 0x3200024 (Cheese)
tammi 17 17:07:50 localhost.localdomain /etc/gdm/Xsession[1521]: Window
manager warning: meta_window_activate called by a pager with a 0
timestamp; the pager needs to be fixed.
tammi 17 17:07:50 localhost.localdomain kernel: tammi 17 17:07:50
localhost.localdomain kernel:
======================================================
tammi 17 17:07:50 localhost.localdomain kernel: [ INFO: possible
circular locking dependency detected ]
tammi 17 17:07:50 localhost.localdomain kernel: 3.13.0-rc1+ #79 Tainted:
G C O
tammi 17 17:07:50 localhost.localdomain kernel:
-------------------------------------------------------
tammi 17 17:07:50 localhost.localdomain kernel: video_source:sr/8871 is
trying to acquire lock:
tammi 17 17:07:50 localhost.localdomain kernel:
(&dev->mutex#2){+.+.+.}, at: [<ffffffffa06a8df3>] vb2_fop_mmap+0x33/0x90
[videobuf2_core]
tammi 17 17:07:50 localhost.localdomain kernel:
but task is already
holding lock:
tammi 17 17:07:50 localhost.localdomain kernel:
(&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0
tammi 17 17:07:50 localhost.localdomain kernel:
which lock already
depends on the new lock.
tammi 17 17:07:50 localhost.localdomain kernel:
the existing dependency
chain (in reverse order) is:
tammi 17 17:07:50 localhost.localdomain kernel:
-> #1
(&mm->mmap_sem){++++++}:
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff810bbca0>] lock_acquire+0xb0/0x150
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff81181f3c>] might_fault+0x8c/0xb0
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffffa067dc15>] video_usercopy+0x375/0x5e0 [videodev]
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffffa067de95>] video_ioctl2+0x15/0x20 [videodev]
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffffa0677703>] v4l2_ioctl+0x123/0x160 [videodev]
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff811e0590>] do_vfs_ioctl+0x300/0x520
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff811e0831>] SyS_ioctl+0x81/0xa0
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
tammi 17 17:07:50 localhost.localdomain kernel:
-> #0
(&dev->mutex#2){+.+.+.}:
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff810b96b7>] validate_chain.isra.36+0x10d7/0x1130
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff810bb386>] __lock_acquire+0x3d6/0xc40
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff810bbca0>] lock_acquire+0xb0/0x150
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff816bf1c7>] mutex_lock_interruptible_nested+0x77/0x460
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffffa06a8df3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffffa067711a>] v4l2_mmap+0x5a/0xa0 [videodev]
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff8118da7d>] mmap_region+0x3cd/0x5a0
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff8118dfa7>] do_mmap_pgoff+0x357/0x3e0
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff81178280>] vm_mmap_pgoff+0x90/0xc0
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff8118c553>] SyS_mmap_pgoff+0x1d3/0x270
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff810191a2>] SyS_mmap+0x22/0x30
tammi 17 17:07:50 localhost.localdomain kernel:
[<ffffffff816ca729>] system_call_fastpath+0x16/0x1b
tammi 17 17:07:50 localhost.localdomain kernel:
other info that might
help us debug this:
tammi 17 17:07:50 localhost.localdomain kernel: Possible unsafe locking
scenario:
tammi 17 17:07:50 localhost.localdomain kernel: CPU0
CPU1
tammi 17 17:07:50 localhost.localdomain kernel: ----
----
tammi 17 17:07:50 localhost.localdomain kernel: lock(&mm->mmap_sem);
tammi 17 17:07:50 localhost.localdomain kernel:
lock(&dev->mutex#2);
tammi 17 17:07:50 localhost.localdomain kernel:
lock(&mm->mmap_sem);
tammi 17 17:07:50 localhost.localdomain kernel: lock(&dev->mutex#2);
tammi 17 17:07:50 localhost.localdomain kernel:
*** DEADLOCK ***
tammi 17 17:07:50 localhost.localdomain kernel: 1 lock held by
video_source:sr/8871:
tammi 17 17:07:50 localhost.localdomain kernel: #0:
(&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0
tammi 17 17:07:50 localhost.localdomain kernel:
stack backtrace:
tammi 17 17:07:50 localhost.localdomain kernel: CPU: 3 PID: 8871 Comm:
video_source:sr Tainted: G C O 3.13.0-rc1+ #79
tammi 17 17:07:50 localhost.localdomain kernel: Hardware name: System
manufacturer System Product Name/M5A78L-M/USB3, BIOS 1801 11/12/2013
tammi 17 17:07:50 localhost.localdomain kernel: ffffffff824f9bd0
ffff880083075b68 ffffffff816b8da9 ffffffff824f9bd0
tammi 17 17:07:50 localhost.localdomain kernel: ffff880083075ba8
ffffffff816b2c9b ffff880083075be0 0000000000000000
tammi 17 17:07:50 localhost.localdomain kernel: ffff8801ee6fc378
0000000000000001 ffff8801ee6fbcf0 ffff8801ee6fc378
tammi 17 17:07:50 localhost.localdomain kernel: Call Trace:
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff816b8da9>]
dump_stack+0x4d/0x66
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff816b2c9b>]
print_circular_bug+0x200/0x20e
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff810b96b7>]
validate_chain.isra.36+0x10d7/0x1130
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff810bb3a7>] ?
__lock_acquire+0x3f7/0xc40
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff8101c413>] ?
native_sched_clock+0x13/0x80
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff810bb386>]
__lock_acquire+0x3d6/0xc40
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff8101c413>] ?
native_sched_clock+0x13/0x80
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff8101c489>] ?
sched_clock+0x9/0x10
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff810bbca0>]
lock_acquire+0xb0/0x150
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffffa06a8df3>] ?
vb2_fop_mmap+0x33/0x90 [videobuf2_core]
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff816bf1c7>]
mutex_lock_interruptible_nested+0x77/0x460
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffffa06a8df3>] ?
vb2_fop_mmap+0x33/0x90 [videobuf2_core]
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffffa06a8df3>] ?
vb2_fop_mmap+0x33/0x90 [videobuf2_core]
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffffa06a8df3>]
vb2_fop_mmap+0x33/0x90 [videobuf2_core]
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffffa067711a>]
v4l2_mmap+0x5a/0xa0 [videodev]
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff8118da7d>]
mmap_region+0x3cd/0x5a0
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff8118dfa7>]
do_mmap_pgoff+0x357/0x3e0
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff81178280>]
vm_mmap_pgoff+0x90/0xc0
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff8118c553>]
SyS_mmap_pgoff+0x1d3/0x270
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff810191a2>]
SyS_mmap+0x22/0x30
tammi 17 17:07:50 localhost.localdomain kernel: [<ffffffff816ca729>]
system_call_fastpath+0x16/0x1b
Regards,
Hans
On 12/29/2013 05:51 AM, Antti Palosaari wrote:
Avoid that lockdep warning:
[ INFO: possible circular locking dependency detected ]
3.13.0-rc1+ #77 Tainted: G C O
-------------------------------------------------------
video_source:sr/32072 is trying to acquire lock:
(&dev->mutex#2){+.+.+.}, at: [<ffffffffa073fde3>] vb2_fop_mmap+0x33/0x90 [videobuf2_core]
but task is already holding lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff8117825f>] vm_mmap_pgoff+0x6f/0xc0
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_sem);
lock(&dev->mutex#2);
lock(&mm->mmap_sem);
lock(&dev->mutex#2);
*** DEADLOCK ***
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
drivers/media/v4l2-core/videobuf2-core.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 12df9fd..2a74295 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -2641,12 +2641,24 @@ int vb2_fop_mmap(struct file *file, struct vm_area_struct *vma)
struct video_device *vdev = video_devdata(file);
struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
int err;
+ /*
+ * FIXME: Ugly hack. Disable possible lockdep as it detects possible
+ * deadlock. "INFO: possible circular locking dependency detected"
+ */
+ lockdep_off();
- if (lock && mutex_lock_interruptible(lock))
+ if (lock && mutex_lock_interruptible(lock)) {
+ lockdep_on();
return -ERESTARTSYS;
+ }
+
err = vb2_mmap(vdev->queue, vma);
+
if (lock)
mutex_unlock(lock);
+
+ lockdep_on();
+
return err;
}
EXPORT_SYMBOL_GPL(vb2_fop_mmap);
--
http://palosaari.fi/
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