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diff --git a/sys/kern/kern_rangelock.c b/sys/kern/kern_rangelock.c
--- a/sys/kern/kern_rangelock.c
+++ b/sys/kern/kern_rangelock.c
@@ -66,7 +66,7 @@
* trylocks are same as normal locks but do not drain.
*/
-static int rangelock_cheat = 0;
+static int rangelock_cheat = 1;
SYSCTL_INT(_debug, OID_AUTO, rangelock_cheat, CTLFLAG_RWTUN,
&rangelock_cheat, 0,
"");
@@ -82,6 +82,24 @@
#define RL_RET_CHEAT_RLOCKED 0x1100
#define RL_RET_CHEAT_WLOCKED 0x2200
+static void
+rangelock_cheat_drain(struct rangelock *lock)
+{
+ uintptr_t v;
+
+ DROP_GIANT();
+ for (;;) {
+ v = (uintptr_t)atomic_load_ptr(&lock->head);
+ if ((v & RL_CHEAT_DRAINING) == 0)
+ break;
+ sleepq_add(&lock->head, NULL, "ranged1", 0, 0);
+ sleepq_wait(&lock->head, PRI_USER);
+ sleepq_lock(&lock->head);
+ }
+ sleepq_release(&lock->head);
+ PICKUP_GIANT();
+}
+
static bool
rangelock_cheat_lock(struct rangelock *lock, int locktype, bool trylock,
void **cookie)
@@ -99,17 +117,7 @@
}
sleepq_lock(&lock->head);
drain1:
- DROP_GIANT();
- for (;;) {
- v = (uintptr_t)atomic_load_ptr(&lock->head);
- if ((v & RL_CHEAT_DRAINING) == 0)
- break;
- sleepq_add(&lock->head, NULL, "ranged1", 0, 0);
- sleepq_wait(&lock->head, PRI_USER);
- sleepq_lock(&lock->head);
- }
- sleepq_release(&lock->head);
- PICKUP_GIANT();
+ rangelock_cheat_drain(lock);
return (false);
}
@@ -744,6 +752,34 @@
return (rangelock_lock_int(lock, true, start, end, RL_LOCK_WRITE));
}
+/*
+ * If the caller asserts that it can obtain the range locks on the
+ * same lock simultaneously, switch to the non-cheat mode. Cheat mode
+ * cannot handle it, hanging in drain or trylock retries.
+ */
+void
+rangelock_may_recurse(struct rangelock *lock)
+{
+ uintptr_t v, x;
+
+ v = (uintptr_t)atomic_load_ptr(&lock->head);
+ if ((v & RL_CHEAT_CHEATING) == 0)
+ return;
+
+ sleepq_lock(&lock->head);
+ for (;;) {
+ if ((v & RL_CHEAT_CHEATING) == 0) {
+ sleepq_release(&lock->head);
+ return;
+ }
+ x = v | RL_CHEAT_DRAINING;
+ if (atomic_fcmpset_rel_ptr(&lock->head, &v, x) != 0)
+ break;
+ }
+
+ rangelock_cheat_drain(lock);
+}
+
#ifdef INVARIANT_SUPPORT
void
_rangelock_cookie_assert(void *cookie, int what, const char *file, int line)
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -4978,11 +4978,13 @@
* If infp and outfp refer to the same file, the byte ranges cannot
* overlap.
*/
- if (invp == outvp && ((savinoff <= savoutoff && savinoff + len >
- savoutoff) || (savinoff > savoutoff && savoutoff + len >
- savinoff))) {
- error = EINVAL;
- goto out;
+ if (invp == outvp) {
+ if ((savinoff <= savoutoff && savinoff + len > savoutoff) ||
+ (savinoff > savoutoff && savoutoff + len > savinoff)) {
+ error = EINVAL;
+ goto out;
+ }
+ rangelock_may_recurse(&invp->v_rl);
}
/* Range lock the byte ranges for both invp and outvp. */
diff --git a/sys/sys/rangelock.h b/sys/sys/rangelock.h
--- a/sys/sys/rangelock.h
+++ b/sys/sys/rangelock.h
@@ -66,6 +66,7 @@
void *rangelock_trywlock(struct rangelock *lock, vm_ooffset_t start,
vm_ooffset_t end);
void rangelock_entry_free(struct rl_q_entry *e);
+void rangelock_may_recurse(struct rangelock *lock);
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
void _rangelock_cookie_assert(void *cookie, int what, const char *file,
int line);

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