git: 8a5b2db3d81d - main - ranglelock_destroy(): do not remove lock entries from under live lock acquirer

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=8a5b2db3d81db16e9e6aaea82cc071bdc766e360

commit 8a5b2db3d81db16e9e6aaea82cc071bdc766e360
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2024-08-09 22:55:36 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2024-08-21 15:18:39 +0000

    ranglelock_destroy(): do not remove lock entries from under live lock acquirer
    
    Tested by:      markj, pho
    Sponsored by:   The FreeBSD Foundation
---
 sys/kern/kern_rangelock.c | 56 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 47 insertions(+), 9 deletions(-)

diff --git a/sys/kern/kern_rangelock.c b/sys/kern/kern_rangelock.c
index c2f1f2d762bb..c01ed05e4a6a 100644
--- a/sys/kern/kern_rangelock.c
+++ b/sys/kern/kern_rangelock.c
@@ -289,6 +289,7 @@ static uma_zone_t rl_entry_zone;
 static smr_t rl_smr;
 
 static void rangelock_free_free(struct rl_q_entry *free);
+static void rangelock_noncheating_destroy(struct rangelock *lock);
 
 static void
 rangelock_sys_init(void)
@@ -340,16 +341,9 @@ rangelock_init(struct rangelock *lock)
 void
 rangelock_destroy(struct rangelock *lock)
 {
-	struct rl_q_entry *e, *ep;
-
 	MPASS(!lock->sleepers);
-	if (rangelock_cheat_destroy(lock))
-		return;
-	for (e = (struct rl_q_entry *)atomic_load_ptr(&lock->head);
-	    e != NULL; e = rl_e_unmark(ep)) {
-		ep = atomic_load_ptr(&e->rl_q_next);
-		uma_zfree_smr(rl_entry_zone, e);
-	}
+	if (!rangelock_cheat_destroy(lock))
+		rangelock_noncheating_destroy(lock);
 }
 
 static bool
@@ -487,6 +481,50 @@ rl_q_cas(struct rl_q_entry **prev, struct rl_q_entry *old,
 	    (uintptr_t)new) != 0);
 }
 
+static void
+rangelock_noncheating_destroy(struct rangelock *lock)
+{
+	struct rl_q_entry *cur, *free, *next, **prev;
+
+	free = NULL;
+again:
+	smr_enter(rl_smr);
+	prev = (struct rl_q_entry **)&lock->head;
+	cur = rl_q_load(prev);
+	MPASS(!rl_e_is_marked(cur));
+
+	for (;;) {
+		if (cur == NULL)
+			break;
+		if (rl_e_is_marked(cur))
+			goto again;
+
+		next = rl_q_load(&cur->rl_q_next);
+		if (rl_e_is_marked(next)) {
+			next = rl_e_unmark(next);
+			if (rl_q_cas(prev, cur, next)) {
+#ifdef INVARIANTS
+				cur->rl_q_owner = NULL;
+#endif
+				cur->rl_q_free = free;
+				free = cur;
+				cur = next;
+				continue;
+			}
+			smr_exit(rl_smr);
+			goto again;
+		}
+
+		sleepq_lock(&lock->sleepers);
+		if (!rl_e_is_marked(cur)) {
+			rl_insert_sleep(lock);
+			goto again;
+		}
+	}
+	smr_exit(rl_smr);
+	rangelock_free_free(free);
+}
+
 enum RL_INSERT_RES {
 	RL_TRYLOCK_FAILED,
 	RL_LOCK_SUCCESS,