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From 4937a4dc4d39cff4badeb727c8d6c1ecf4422a0d Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 25 Apr 2023 17:03:13 +0200
Subject: [PATCH 56/62] debugobjects,locking: Annotate debug_object_fill_pool()
wait type violation
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
(cherry picked from commit 0cce06ba859a515bd06224085d3addb870608b6d)
Signed-off-by: Clark Williams <clark.williams@gmail.com>
---
include/linux/lockdep.h | 14 ++++++++++++++
include/linux/lockdep_types.h | 1 +
kernel/locking/lockdep.c | 28 +++++++++++++++++++++-------
lib/debugobjects.c | 15 +++++++++++++--
4 files changed, 49 insertions(+), 9 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 1023f349af71..a3329fb49b33 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -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_)
diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index d22430840b53..59f4fb1626ea 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -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,
};
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 3b38303ed27b..a046e03c7ead 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2245,6 +2245,9 @@ 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.
*
@@ -2271,14 +2274,16 @@ 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;
}
/*
@@ -4745,7 +4750,8 @@ 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) {
/*
@@ -4755,6 +4761,14 @@ 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;
}
}
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index dacb80c22c4f..3c9e00e207dc 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -600,10 +600,21 @@ 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
--
2.43.0
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