diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2025-02-28 16:07:18 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2025-02-28 16:07:18 -0800 |
| commit | 405a41d7599be266ae6880e73252ca41770760fe (patch) | |
| tree | 1b9c7919feaedd1ad42c0e81b1bb30727a791377 | |
| parent | 5c44ddaf7df3a06391684dde65083a092e06052b (diff) | |
| parent | b9a49520679e98700d3d89689cc91c08a1c88c1d (diff) | |
Merge tag 'locking-urgent-2025-02-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fix from Ingo Molnar:
"Fix an rcuref_put() slowpath race"
* tag 'locking-urgent-2025-02-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcuref: Plug slowpath race in rcuref_put()
| -rw-r--r-- | include/linux/rcuref.h | 9 | ||||
| -rw-r--r-- | lib/rcuref.c | 5 |
2 files changed, 8 insertions, 6 deletions
diff --git a/include/linux/rcuref.h b/include/linux/rcuref.h index 2c8bfd0f1b6b..6322d8c1c6b4 100644 --- a/include/linux/rcuref.h +++ b/include/linux/rcuref.h @@ -71,27 +71,30 @@ static inline __must_check bool rcuref_get(rcuref_t *ref) return rcuref_get_slowpath(ref); } -extern __must_check bool rcuref_put_slowpath(rcuref_t *ref); +extern __must_check bool rcuref_put_slowpath(rcuref_t *ref, unsigned int cnt); /* * Internal helper. Do not invoke directly. */ static __always_inline __must_check bool __rcuref_put(rcuref_t *ref) { + int cnt; + RCU_LOCKDEP_WARN(!rcu_read_lock_held() && preemptible(), "suspicious rcuref_put_rcusafe() usage"); /* * Unconditionally decrease the reference count. The saturation and * dead zones provide enough tolerance for this. */ - if (likely(!atomic_add_negative_release(-1, &ref->refcnt))) + cnt = atomic_sub_return_release(1, &ref->refcnt); + if (likely(cnt >= 0)) return false; /* * Handle the last reference drop and cases inside the saturation * and dead zones. */ - return rcuref_put_slowpath(ref); + return rcuref_put_slowpath(ref, cnt); } /** diff --git a/lib/rcuref.c b/lib/rcuref.c index 97f300eca927..5bd726b71e39 100644 --- a/lib/rcuref.c +++ b/lib/rcuref.c @@ -220,6 +220,7 @@ EXPORT_SYMBOL_GPL(rcuref_get_slowpath); /** * rcuref_put_slowpath - Slowpath of __rcuref_put() * @ref: Pointer to the reference count + * @cnt: The resulting value of the fastpath decrement * * Invoked when the reference count is outside of the valid zone. * @@ -233,10 +234,8 @@ EXPORT_SYMBOL_GPL(rcuref_get_slowpath); * with a concurrent get()/put() pair. Caller is not allowed to * deconstruct the protected object. */ -bool rcuref_put_slowpath(rcuref_t *ref) +bool rcuref_put_slowpath(rcuref_t *ref, unsigned int cnt) { - unsigned int cnt = atomic_read(&ref->refcnt); - /* Did this drop the last reference? */ if (likely(cnt == RCUREF_NOREF)) { /* |