Bug#619827: linux-source-2.6.38: [linux-dvb] cx88-blackbird broken (since 2.6.37)
Package: linux-source-2.6.38
Version: 2.6.38-1
Severity: important
Tags: upstream
[Symptom]
Processes that try to open a cx88-blackbird driven MPEG device will hang up.
[Cause]
Nestet mutex_locks (which are not allowed) result in a deadlock.
[Details]
There has been resent work on removing BKL (BigKernelLock) calls from kernel code. (see http://kernelnewbies.org/BigKernelLock) This was not properly done for the cx88-blackbird driver:
Source-File: drivers/media/video/cx88/cx88-blackbird.c
Function: int mpeg_open(struct file *file)
Problem: the calls to drv->request_acquire(drv); and drv->request_release(drv); will hang because they try to lock a mutex that has already been locked by a previouse call to mutex_lock(&dev->core->lock) ...
1050 static int mpeg_open(struct file *file)
1051 {
[...]
1060 mutex_lock(&dev->core->lock); // MUTEX LOCKED !!!!!!!!!!!!!!!!
1061
1062 /* Make sure we can acquire the hardware */
1063 drv = cx8802_get_driver(dev, CX88_MPEG_BLACKBIRD);
1064 if (drv) {
1065 err = drv->request_acquire(drv); // HANGS !!!!!!!!!!!!!!!!!!!
1066 if(err != 0) {
1067 dprintk(1,"%s: Unable to acquire hardware, %d\n", __func__, err);
1068 mutex_unlock(&dev->core->lock);;
1069 return err;
1070 }
1071 }
[...]
Here's the relevant kernel log extract (Linux version 2.6.38-1-amd64 (Debian 2.6.38-1)) ...
Mar 24 21:25:10 xen kernel: [ 241.472067] INFO: task v4l_id:1000 blocked for more than 120 seconds.
Mar 24 21:25:10 xen kernel: [ 241.478845] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 24 21:25:10 xen kernel: [ 241.482412] v4l_id D ffff88006bcb6540 0 1000 1 0x00000000
Mar 24 21:25:10 xen kernel: [ 241.486031] ffff88006bcb6540 0000000000000086 ffff880000000001 ffff88006981c380
Mar 24 21:25:10 xen kernel: [ 241.489694] 0000000000013700 ffff88006be5bfd8 ffff88006be5bfd8 0000000000013700
Mar 24 21:25:10 xen kernel: [ 241.493301] ffff88006bcb6540 ffff88006be5a010 ffff88006bcb6540 000000016be5a000
Mar 24 21:25:10 xen kernel: [ 241.496766] Call Trace:
Mar 24 21:25:10 xen kernel: [ 241.500145] [<ffffffff81321c4a>] ? __mutex_lock_common+0x127/0x193
Mar 24 21:25:10 xen kernel: [ 241.503630] [<ffffffff81321d82>] ? mutex_lock+0x1a/0x33
Mar 24 21:25:10 xen kernel: [ 241.507145] [<ffffffffa09dd155>] ? cx8802_request_acquire+0x66/0xc6 [cx8802]
Mar 24 21:25:10 xen kernel: [ 241.510699] [<ffffffffa0aab7f2>] ? mpeg_open+0x7a/0x1fc [cx88_blackbird]
Mar 24 21:25:10 xen kernel: [ 241.514279] [<ffffffff8123bfb6>] ? kobj_lookup+0x139/0x173
Mar 24 21:25:10 xen kernel: [ 241.517856] [<ffffffffa062d5fd>] ? v4l2_open+0xb3/0xdf [videodev]
regards
Andi Huber
-- System Information:
Debian Release: wheezy/sid
APT prefers unstable
APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.36-trunk-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.ISO-8859-15, LC_CTYPE=en_US.ISO-8859-15 (charmap=ISO-8859-15)
Shell: /bin/sh linked to /bin/dash
Versions of packages linux-source-2.6.38 depends on:
ii binutils 2.20.1-16 The GNU assembler, linker and bina
ii bzip2 1.0.5-6 high-quality block-sorting file co
Versions of packages linux-source-2.6.38 recommends:
ii gcc 4:4.4.5-1 The GNU C compiler
ii libc6-dev [libc-dev] 2.11.2-10 Embedded GNU C Library: Developmen
ii make 3.81-8 An utility for Directing compilati
Versions of packages linux-source-2.6.38 suggests:
pn kernel-package <none> (no description available)
ii libncurses5-dev [ncurses- 5.8+20110307-1 developer's libraries for ncurses
pn libqt3-mt-dev <none> (no description available)
-- no debconf information
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