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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-08-11 11:30:24 +0400
committerIngo Molnar <mingo@elte.hu>2008-08-11 11:30:24 +0400
commit7531e2f34d1d551b096143f19111139f0dd84c8b (patch)
tree0a29d6703e28dc6752b9b4085594cca238595aac /include/linux
parent4f3e7524b2e703d9f8b02ac338153a53dd7ede66 (diff)
downloadlinux-7531e2f34d1d551b096143f19111139f0dd84c8b.tar.xz
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')
-rw-r--r--include/linux/lockdep.h34
-rw-r--r--include/linux/rcuclassic.h2
2 files changed, 19 insertions, 17 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
diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h
index 8c774905dcfe..4ab843622727 100644
--- a/include/linux/rcuclassic.h
+++ b/include/linux/rcuclassic.h
@@ -117,7 +117,7 @@ extern int rcu_needs_cpu(int cpu);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern struct lockdep_map rcu_lock_map;
# define rcu_read_acquire() \
- lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
+ lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
#else
# define rcu_read_acquire() do { } while (0)