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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2008-08-11 09:30:24 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-08-11 09:30:24 +0200 |
commit | 7531e2f34d1d551b096143f19111139f0dd84c8b (patch) | |
tree | 0a29d6703e28dc6752b9b4085594cca238595aac /include/linux/lockdep.h | |
parent | 4f3e7524b2e703d9f8b02ac338153a53dd7ede66 (diff) | |
download | linux-stable-7531e2f34d1d551b096143f19111139f0dd84c8b.tar.gz linux-stable-7531e2f34d1d551b096143f19111139f0dd84c8b.tar.bz2 linux-stable-7531e2f34d1d551b096143f19111139f0dd84c8b.zip |
lockdep: lock protection locks
On Fri, 2008-08-01 at 16:26 -0700, Linus Torvalds wrote:
> On Fri, 1 Aug 2008, David Miller wrote:
> >
> > Taking more than a few locks of the same class at once is bad
> > news and it's better to find an alternative method.
>
> It's not always wrong.
>
> If you can guarantee that anybody that takes more than one lock of a
> particular class will always take a single top-level lock _first_, then
> that's all good. You can obviously screw up and take the same lock _twice_
> (which will deadlock), but at least you cannot get into ABBA situations.
>
> So maybe the right thing to do is to just teach lockdep about "lock
> protection locks". That would have solved the multi-queue issues for
> networking too - all the actual network drivers would still have taken
> just their single queue lock, but the one case that needs to take all of
> them would have taken a separate top-level lock first.
>
> Never mind that the multi-queue locks were always taken in the same order:
> it's never wrong to just have some top-level serialization, and anybody
> who needs to take <n> locks might as well do <n+1>, because they sure as
> hell aren't going to be on _any_ fastpaths.
>
> So the simplest solution really sounds like just teaching lockdep about
> that one special case. It's not "nesting" exactly, although it's obviously
> related to it.
Do as Linus suggested. The lock protection lock is called nest_lock.
Note that we still have the MAX_LOCK_DEPTH (48) limit to consider, so anything
that spills that it still up shit creek.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/lockdep.h')
-rw-r--r-- | include/linux/lockdep.h | 34 |
1 files changed, 18 insertions, 16 deletions
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index e431d1d6eaf3..93a8cc02a033 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -211,6 +211,7 @@ struct held_lock { u64 prev_chain_key; unsigned long acquire_ip; struct lockdep_map *instance; + struct lockdep_map *nest_lock; #ifdef CONFIG_LOCK_STAT u64 waittime_stamp; u64 holdtime_stamp; @@ -297,7 +298,8 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name, * 2: full validation */ extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass, - int trylock, int read, int check, unsigned long ip); + int trylock, int read, int check, + struct lockdep_map *nest_lock, unsigned long ip); extern void lock_release(struct lockdep_map *lock, int nested, unsigned long ip); @@ -319,7 +321,7 @@ static inline void lockdep_on(void) { } -# define lock_acquire(l, s, t, r, c, i) do { } while (0) +# define lock_acquire(l, s, t, r, c, n, i) do { } while (0) # define lock_release(l, n, i) do { } while (0) # define lock_set_subclass(l, s, i) do { } while (0) # define lockdep_init() do { } while (0) @@ -407,9 +409,9 @@ static inline void print_irqtrace_events(struct task_struct *curr) #ifdef CONFIG_DEBUG_LOCK_ALLOC # ifdef CONFIG_PROVE_LOCKING -# define spin_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i) +# define spin_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, NULL, i) # else -# define spin_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i) +# define spin_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, NULL, i) # endif # define spin_release(l, n, i) lock_release(l, n, i) #else @@ -419,11 +421,11 @@ static inline void print_irqtrace_events(struct task_struct *curr) #ifdef CONFIG_DEBUG_LOCK_ALLOC # ifdef CONFIG_PROVE_LOCKING -# define rwlock_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i) -# define rwlock_acquire_read(l, s, t, i) lock_acquire(l, s, t, 2, 2, i) +# define rwlock_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, NULL, i) +# define rwlock_acquire_read(l, s, t, i) lock_acquire(l, s, t, 2, 2, NULL, i) # else -# define rwlock_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i) -# define rwlock_acquire_read(l, s, t, i) lock_acquire(l, s, t, 2, 1, i) +# define rwlock_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, NULL, i) +# define rwlock_acquire_read(l, s, t, i) lock_acquire(l, s, t, 2, 1, NULL, i) # endif # define rwlock_release(l, n, i) lock_release(l, n, i) #else @@ -434,9 +436,9 @@ static inline void print_irqtrace_events(struct task_struct *curr) #ifdef CONFIG_DEBUG_LOCK_ALLOC # ifdef CONFIG_PROVE_LOCKING -# define mutex_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i) +# define mutex_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, NULL, i) # else -# define mutex_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i) +# define mutex_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, NULL, i) # endif # define mutex_release(l, n, i) lock_release(l, n, i) #else @@ -446,11 +448,11 @@ static inline void print_irqtrace_events(struct task_struct *curr) #ifdef CONFIG_DEBUG_LOCK_ALLOC # ifdef CONFIG_PROVE_LOCKING -# define rwsem_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, i) -# define rwsem_acquire_read(l, s, t, i) lock_acquire(l, s, t, 1, 2, i) +# define rwsem_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 2, NULL, i) +# define rwsem_acquire_read(l, s, t, i) lock_acquire(l, s, t, 1, 2, NULL, i) # else -# define rwsem_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, i) -# define rwsem_acquire_read(l, s, t, i) lock_acquire(l, s, t, 1, 1, i) +# define rwsem_acquire(l, s, t, i) lock_acquire(l, s, t, 0, 1, NULL, i) +# define rwsem_acquire_read(l, s, t, i) lock_acquire(l, s, t, 1, 1, NULL, i) # endif # define rwsem_release(l, n, i) lock_release(l, n, i) #else @@ -461,9 +463,9 @@ static inline void print_irqtrace_events(struct task_struct *curr) #ifdef CONFIG_DEBUG_LOCK_ALLOC # ifdef CONFIG_PROVE_LOCKING -# define map_acquire(l) lock_acquire(l, 0, 0, 0, 2, _THIS_IP_) +# define map_acquire(l) lock_acquire(l, 0, 0, 0, 2, NULL, _THIS_IP_) # else -# define map_acquire(l) lock_acquire(l, 0, 0, 0, 1, _THIS_IP_) +# define map_acquire(l) lock_acquire(l, 0, 0, 0, 1, NULL, _THIS_IP_) # endif # define map_release(l) lock_release(l, 1, _THIS_IP_) #else |