Messages in this thread Patch in this message | | | Date | Thu, 19 May 2016 10:32:32 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner field |
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On Thu, May 19, 2016 at 11:37:53AM +1000, Dave Chinner wrote: > On Fri, May 06, 2016 at 08:20:24PM -0400, Waiman Long wrote: > > Currently, it is not possible to determine for sure if a reader > > owns a rwsem by looking at the content of the rwsem data structure. > > This patch adds a new state RWSEM_READER_OWNED to the owner field > > to indicate that readers currently own the lock. > > Oh, yes please. This will enable us to get rid of the remaining > mrlock rwsem abstraction we've carried since the days of Irix in > XFS. The only reason the abstraction still exists is that we track > write locks for the purposes of checking for correct inode locking > contexts via ASSERT(xfs_isilocked()) calls....
That all seems to live under a DEBUG knob; lockdep could also easily tell you these things.
--- include/linux/lockdep.h | 36 +++++++++++++++++++++++++++++------- kernel/locking/lockdep.c | 19 ++++++++++++------- 2 files changed, 41 insertions(+), 14 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index eabe0138eb06..82d6453c4660 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -338,9 +338,21 @@ extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass, extern void lock_release(struct lockdep_map *lock, int nested, unsigned long ip); -#define lockdep_is_held(lock) lock_is_held(&(lock)->dep_map) +#define LOCKDEP_HELD_ANY (-1) +#define LOCKDEP_HELD_EXCLUSIVE (0) +#define LOCKDEP_HELD_SHARED (1) +#define LOCKDEP_HELD_RECURSIVE (2) -extern int lock_is_held(struct lockdep_map *lock); +extern int _lock_is_held(struct lockdep_map *lock, int read); + +static inline int lock_is_held(struct lockdep_map *lock) +{ + return _lock_is_held(lock, LOCKDEP_HELD_ANY); +} + +#define lockdep_is_held(lock) _lock_is_held(&(lock)->dep_map, LOCKDEP_HELD_ANY) +#define lockdep_is_held_exclusive(lock) _lock_is_held(&(lock)->dep_map, LOCKDEP_HELD_EXCLUSIVE) +#define lockdep_is_held_shared(lock) _lock_is_held(&(lock)->dep_map, LOCKDEP_HELD_SHARED) extern void lock_set_class(struct lockdep_map *lock, const char *name, struct lock_class_key *key, unsigned int subclass, @@ -369,12 +381,20 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) #define lockdep_assert_held(l) do { \ - WARN_ON(debug_locks && !lockdep_is_held(l)); \ - } while (0) + WARN_ON(debug_locks && !lockdep_is_held(l)); \ +} while (0) -#define lockdep_assert_held_once(l) do { \ - WARN_ON_ONCE(debug_locks && !lockdep_is_held(l)); \ - } while (0) +#define lockdep_assert_held_once(l) do { \ + WARN_ON_ONCE(debug_locks && !lockdep_is_held(l)); \ +} while (0) + +#define lockdep_assert_held_exclusive(l) do { \ + WARN_ON(debug_locks && !lockdep_is_held_exclusive(l)); \ +} while (0) + +#define lockdep_assert_held_shared(l) do { \ + WARN_ON(debug_locks && !lockdep_is_held_shared(l)); \ +} while (0) #define lockdep_recursing(tsk) ((tsk)->lockdep_recursion) @@ -430,6 +450,8 @@ struct lock_class_key { }; #define lockdep_assert_held(l) do { (void)(l); } while (0) #define lockdep_assert_held_once(l) do { (void)(l); } while (0) +#define lockdep_assert_held_exclusive(l) do { (void)(l); } while (0) +#define lockdep_assert_held_shared(l) do { (void)(l); } while (0) #define lockdep_recursing(tsk) (0) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 81f1a7107c0e..dca5d982b315 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3183,7 +3183,7 @@ print_lock_nested_lock_not_held(struct task_struct *curr, return 0; } -static int __lock_is_held(struct lockdep_map *lock); +static int __lock_is_held(struct lockdep_map *lock, int read); /* * This gets called for every mutex_lock*()/spin_lock*() operation. @@ -3324,7 +3324,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, } chain_key = iterate_chain_key(chain_key, class_idx); - if (nest_lock && !__lock_is_held(nest_lock)) + if (nest_lock && !__lock_is_held(nest_lock, LOCKDEP_HELD_ANY)) return print_lock_nested_lock_not_held(curr, hlock, ip); if (!validate_chain(curr, lock, hlock, chain_head, chain_key)) @@ -3571,7 +3571,7 @@ __lock_release(struct lockdep_map *lock, int nested, unsigned long ip) return 1; } -static int __lock_is_held(struct lockdep_map *lock) +static int __lock_is_held(struct lockdep_map *lock, int read) { struct task_struct *curr = current; int i; @@ -3579,8 +3579,13 @@ static int __lock_is_held(struct lockdep_map *lock) for (i = 0; i < curr->lockdep_depth; i++) { struct held_lock *hlock = curr->held_locks + i; - if (match_held_lock(hlock, lock)) + if (!match_held_lock(hlock, lock)) + continue; + + if (read == LOCKDEP_HELD_ANY) return 1; + + return read == hlock->read; } return 0; @@ -3764,7 +3769,7 @@ void lock_release(struct lockdep_map *lock, int nested, } EXPORT_SYMBOL_GPL(lock_release); -int lock_is_held(struct lockdep_map *lock) +int _lock_is_held(struct lockdep_map *lock, int read) { unsigned long flags; int ret = 0; @@ -3776,13 +3781,13 @@ int lock_is_held(struct lockdep_map *lock) check_flags(flags); current->lockdep_recursion = 1; - ret = __lock_is_held(lock); + ret = __lock_is_held(lock, read); current->lockdep_recursion = 0; raw_local_irq_restore(flags); return ret; } -EXPORT_SYMBOL_GPL(lock_is_held); +EXPORT_SYMBOL_GPL(_lock_is_held); struct pin_cookie lock_pin_lock(struct lockdep_map *lock) {
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