Messages in this thread Patch in this message | | | Subject | Re: [2.6.25-rc5-mm1] BUG() at mnt_want_write(). | From | Peter Zijlstra <> | Date | Wed, 12 Mar 2008 10:25:18 +0100 |
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On Tue, 2008-03-11 at 20:22 -0700, Andrew Morton wrote: > On Tue, 11 Mar 2008 20:03:30 -0700 Dave Hansen <haveblue@us.ibm.com> wrote: > > > On Wed, 2008-03-12 at 10:37 +0900, penguin-kernel@i-love.sakura.ne.jp > > ... > > > checking TSC synchronization [CPU#0 -> CPU#1]: passed. > > > Brought up 2 CPUs > > > khelper used greatest stack depth: 2684 bytes left > > > net_namespace: 320 bytes > > > NET: Registered protocol family 16 > > > INFO: trying to register non-static key.
It means the lock_class_key ended up in non-static storage.
In practise it often means you initialized a on-stack structure incorrectly. DECLARE_WAIT_QUEUE_HEAD() vs DECLARE_WAIT_QUEUE_HEAD_ONSTACK() for example.
> > > the code is fine but needs lockdep annotation. > > > turning off the locking correctness validator. > > > Pid: 1, comm: swapper Not tainted 2.6.25-rc5-mm1 #1 > > > [<c013dd91>] __lock_acquire+0x194/0x6a3 > > > [<c0167ded>] ? cache_free_debugcheck+0x1fd/0x219 > > > [<c0168938>] ? kfree+0xdb/0xe5 > > > [<c013e775>] lock_acquire+0x6a/0x87 > > > [<c01368e4>] ? down+0xc/0x2f > > > [<c03492b1>] _spin_lock_irqsave+0x25/0x55 > > > [<c01368e4>] ? down+0xc/0x2f > > > [<c01368e4>] down+0xc/0x2f > > > [<c022caf3>] device_add+0x152/0x243 > > > [<c022cbf6>] device_register+0x12/0x15 > > > [<c022ce9b>] device_create+0x76/0x90 > > > [<c04a1861>] vtconsole_class_init+0x72/0xb9 > > > [<c048d8ae>] ? kernel_init+0x0/0x88 > > > [<c048d784>] do_initcalls+0x59/0x134 > > > [<c014bcb1>] ? register_irq_proc+0xb1/0xca > > > [<c01a0000>] ? proc_symlink+0x5/0x73 > > > [<c048d8ae>] ? kernel_init+0x0/0x88 > > > [<c048d87b>] do_basic_setup+0x1c/0x1e > > > [<c048d8fb>] kernel_init+0x4d/0x88 > > > [<c01045b7>] kernel_thread_helper+0x7/0x10 > > > ======================= > >
/me & git fetch mm && git checkout mm/v2.6.25-rc5-mm1
/me twiddles thumbs..
/me tries to untangle the sysfs stuff, finds nothing wrong, looks at semaphore code, and.. the winner is: Matthew messed up the semaphores.
Tssk, rewriting locking primitives and not using lockdep...
Compile tested defconfig with lockdep and !lockdep.
--- Subject: lockdep: fixup the new semaphore implementation
The new semaphores failed to properly initialize its spinlock. Non static spinlocks should use spin_lock_init(). Alternatively you should supply a static key yourself.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- include/linux/semaphore.h | 4 ++++ 1 file changed, 4 insertions(+)
Index: linux-2.6/include/linux/semaphore.h =================================================================== --- linux-2.6.orig/include/linux/semaphore.h +++ linux-2.6/include/linux/semaphore.h @@ -41,7 +41,11 @@ struct semaphore { static inline void sema_init(struct semaphore *sem, int val) { + static struct lock_class_key __key; + *sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val); + + lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0); } #define init_MUTEX(sem) sema_init(sem, 1)
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