On Thu, Aug 11, 2016 at 10:10:23AM -0700, Christoph Hellwig wrote:
> There is one major issue with this change though: lockdep currently
> doesn't have a facility to assert a rw_sempahore is held exclusively,
> which means we lose the nice ability to assert locking context in
> XFS.
>
> Peter, I think you mentioned this would be fairly easy to add to
> lockdep and the rw_semaphore code. Any chance to come up with a proof
> of concept?
Sure, find below. Not been near a compiler.
---
include/linux/lockdep.h | 17 +++++++++++++++--
kernel/locking/lockdep.c | 41 +++++++++++++++++++++++++----------------
2 files changed, 40 insertions(+), 18 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index eabe0138eb06..7f0098d3a7d7 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -338,9 +338,14 @@ 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)
+extern int _lock_is_held(struct lockdep_map *lock, int read);
-extern int lock_is_held(struct lockdep_map *lock);
+static inline int lock_is_held(struct lockdep_map *lock)
+{
+ return _lock_is_held(lock, -1);
+}
+
+#define lockdep_is_held(lock) lock_is_held(&(lock)->dep_map)
extern void lock_set_class(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, unsigned int subclass,
@@ -372,6 +377,14 @@ extern void lock_unpin_lock(struct lockdep_map *lock,
struct pin_cookie);
WARN_ON(debug_locks && !lockdep_is_held(l)); \
} while (0)
+#define lockdep_assert_held_exclusive(l) do { \
+ WARN_ON(debug_locks && !_lockdep_is_held(l, 0));\
+ } while (0)
+
+#define lockdep_assert_held_read(l) do { \
+ WARN_ON(debug_locks && !_lockdep_is_held(l, 1));\
+ } while (0)
+
#define lockdep_assert_held_once(l) do { \
WARN_ON_ONCE(debug_locks && !lockdep_is_held(l)); \
} while (0)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 589d763a49b3..abec578378e7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3188,7 +3188,7 @@ 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.
@@ -3329,7 +3329,7 @@ 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, -1))
return print_lock_nested_lock_not_held(curr, hlock, ip);
if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
@@ -3390,10 +3390,17 @@ print_unlock_imbalance_bug(struct task_struct *curr,
struct lockdep_map *lock,
return 0;
}
-static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
+static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock,
int read)
{
- if (hlock->instance == lock)
- return 1;
+ if (hlock->instance == lock) {
+ if (read == -1)
+ return 1;
+
+ if (hlock->read == read)
+ return 1;
+
+ return 0;
+ }
if (hlock->references) {
struct lock_class *class = lock->class_cache[0];
@@ -3420,6 +3427,8 @@ static int match_held_lock(struct held_lock *hlock,
struct lockdep_map *lock)
if (hlock->class_idx == class - lock_classes + 1)
return 1;
+
+ /* XXX do we want @read stuff for nested locks !? */
}
return 0;
@@ -3452,7 +3461,7 @@ __lock_set_class(struct lockdep_map *lock, const char
*name,
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
- if (match_held_lock(hlock, lock))
+ if (match_held_lock(hlock, lock, -1))
goto found_it;
prev_hlock = hlock;
}
@@ -3523,7 +3532,7 @@ __lock_release(struct lockdep_map *lock, int nested,
unsigned long ip)
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
- if (match_held_lock(hlock, lock))
+ if (match_held_lock(hlock, lock, -1))
goto found_it;
prev_hlock = hlock;
}
@@ -3576,7 +3585,7 @@ __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;
@@ -3584,7 +3593,7 @@ 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, read))
return 1;
}
@@ -3603,7 +3612,7 @@ static struct pin_cookie __lock_pin_lock(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, -1)) {
/*
* Grab 16bits of randomness; this is sufficient to not
* be guessable and still allows some pin nesting in
@@ -3630,7 +3639,7 @@ static void __lock_repin_lock(struct lockdep_map *lock,
struct pin_cookie cookie
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, -1)) {
hlock->pin_count += cookie.val;
return;
}
@@ -3650,7 +3659,7 @@ static void __lock_unpin_lock(struct lockdep_map *lock,
struct pin_cookie cookie
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, -1)) {
if (WARN(!hlock->pin_count, "unpinning an unpinned
lock\n"))
return;
@@ -3769,7 +3778,7 @@ 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;
@@ -3781,7 +3790,7 @@ 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);
@@ -3908,7 +3917,7 @@ __lock_contended(struct lockdep_map *lock, unsigned long
ip)
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
- if (match_held_lock(hlock, lock))
+ if (match_held_lock(hlock, lock, -1))
goto found_it;
prev_hlock = hlock;
}
@@ -3961,7 +3970,7 @@ __lock_acquired(struct lockdep_map *lock, unsigned long
ip)
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
- if (match_held_lock(hlock, lock))
+ if (match_held_lock(hlock, lock, -1))
goto found_it;
prev_hlock = hlock;
}
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