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debugobjects,locking: Annotate debug_object_fill_pool() wait type violation

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There is an explicit wait-type violation in debug_object_fill_pool()
for PREEMPT_RT=n kernels which allows them to more easily fill the
object pool and reduce the chance of allocation failures.

Lockdep's wait-type checks are designed to check the PREEMPT_RT
locking rules even for PREEMPT_RT=n kernels and object to this, so
create a lockdep annotation to allow this to stand.

Specifically, create a 'lock' type that overrides the inner wait-type
while it is held -- allowing one to temporarily raise it, such that
the violation is hidden.

Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Qi Zheng <zhengqi.arch@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Qi Zheng <zhengqi.arch@bytedance.com>
Link: https://lkml.kernel.org/r/20230429100614.GA1489784@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2023-04-25 17:03:13 +02:00
parent 0af462f19e
commit 0cce06ba85
4 changed files with 49 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/lockdep.h
View File

@ -339,6 +339,16 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
#define lockdep_repin_lock(l,c) lock_repin_lock(&(l)->dep_map, (c))
#define lockdep_unpin_lock(l,c) lock_unpin_lock(&(l)->dep_map, (c))
/*
* Must use lock_map_aquire_try() with override maps to avoid
* lockdep thinking they participate in the block chain.
*/
#define DEFINE_WAIT_OVERRIDE_MAP(_name, _wait_type) \
struct lockdep_map _name = { \
.name = #_name "-wait-type-override", \
.wait_type_inner = _wait_type, \
.lock_type = LD_LOCK_WAIT_OVERRIDE, }
#else /* !CONFIG_LOCKDEP */
static inline void lockdep_init_task(struct task_struct *task)
@ -427,6 +437,9 @@ extern int lockdep_is_held(const void *);
#define lockdep_repin_lock(l, c) do { (void)(l); (void)(c); } while (0)
#define lockdep_unpin_lock(l, c) do { (void)(l); (void)(c); } while (0)
#define DEFINE_WAIT_OVERRIDE_MAP(_name, _wait_type) \
struct lockdep_map __maybe_unused _name = {}
#endif /* !LOCKDEP */
enum xhlock_context_t {
@ -551,6 +564,7 @@ do { \
#define rwsem_release(l, i) lock_release(l, i)
#define lock_map_acquire(l) lock_acquire_exclusive(l, 0, 0, NULL, _THIS_IP_)
#define lock_map_acquire_try(l) lock_acquire_exclusive(l, 0, 1, NULL, _THIS_IP_)
#define lock_map_acquire_read(l) lock_acquire_shared_recursive(l, 0, 0, NULL, _THIS_IP_)
#define lock_map_acquire_tryread(l) lock_acquire_shared_recursive(l, 0, 1, NULL, _THIS_IP_)
#define lock_map_release(l) lock_release(l, _THIS_IP_)

1
include/linux/lockdep_types.h
View File

@ -33,6 +33,7 @@ enum lockdep_wait_type {
enum lockdep_lock_type {
LD_LOCK_NORMAL = 0, /* normal, catch all */
LD_LOCK_PERCPU, /* percpu */
LD_LOCK_WAIT_OVERRIDE, /* annotation */
LD_LOCK_MAX,
};

28
kernel/locking/lockdep.c
View File

@ -2253,6 +2253,9 @@ static inline bool usage_match(struct lock_list *entry, void *mask)
static inline bool usage_skip(struct lock_list *entry, void *mask)
{
if (entry->class->lock_type == LD_LOCK_NORMAL)
return false;
/*
* Skip local_lock() for irq inversion detection.
*
@ -2279,14 +2282,16 @@ static inline bool usage_skip(struct lock_list *entry, void *mask)
* As a result, we will skip local_lock(), when we search for irq
* inversion bugs.
*/
if (entry->class->lock_type == LD_LOCK_PERCPU) {
if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
return false;
if (entry->class->lock_type == LD_LOCK_PERCPU &&
DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
return false;
return true;
}
/*
* Skip WAIT_OVERRIDE for irq inversion detection -- it's not actually
* a lock and only used to override the wait_type.
*/
return false;
return true;
}
/*
@ -4752,7 +4757,8 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
for (; depth < curr->lockdep_depth; depth++) {
struct held_lock *prev = curr->held_locks + depth;
u8 prev_inner = hlock_class(prev)->wait_type_inner;
struct lock_class *class = hlock_class(prev);
u8 prev_inner = class->wait_type_inner;
if (prev_inner) {
/*
@ -4762,6 +4768,14 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
* Also due to trylocks.
*/
curr_inner = min(curr_inner, prev_inner);
/*
* Allow override for annotations -- this is typically
* only valid/needed for code that only exists when
* CONFIG_PREEMPT_RT=n.
*/
if (unlikely(class->lock_type == LD_LOCK_WAIT_OVERRIDE))
curr_inner = prev_inner;
}
}

15
lib/debugobjects.c
View File

@ -591,10 +591,21 @@ static void debug_objects_fill_pool(void)
{
/*
* On RT enabled kernels the pool refill must happen in preemptible
* context:
* context -- for !RT kernels we rely on the fact that spinlock_t and
* raw_spinlock_t are basically the same type and this lock-type
* inversion works just fine.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible())
if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
/*
* Annotate away the spinlock_t inside raw_spinlock_t warning
* by temporarily raising the wait-type to WAIT_SLEEP, matching
* the preemptible() condition above.
*/
static DEFINE_WAIT_OVERRIDE_MAP(fill_pool_map, LD_WAIT_SLEEP);
lock_map_acquire_try(&fill_pool_map);
fill_pool();
lock_map_release(&fill_pool_map);
}
}
static void