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Protect against a race between granting a lock and accessing
other parts of the lock. Submitted by: davidxu
This commit is contained in:
Daniel Eischen
parent
0eda4c08a5
commit
c72cd7c9e2
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=114680
@ -65,6 +65,7 @@ _lock_init(struct lock *lck, enum lock_type ltype,
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lck->l_head->lr_watcher = NULL;
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lck->l_head->lr_owner = NULL;
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lck->l_head->lr_waiting = 0;
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lck->l_head->lr_handshake = 0;
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lck->l_tail = lck->l_head;
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}
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return (0);
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@ -84,6 +85,7 @@ _lockuser_init(struct lockuser *lu, void *priv)
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lu->lu_myreq->lr_watcher = NULL;
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lu->lu_myreq->lr_owner = lu;
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lu->lu_myreq->lr_waiting = 0;
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lu->lu_myreq->lr_handshake = 0;
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lu->lu_watchreq = NULL;
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lu->lu_priority = 0;
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lu->lu_private = priv;
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@ -169,6 +171,12 @@ _lock_acquire(struct lock *lck, struct lockuser *lu, int prio)
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while (lu->lu_watchreq->lr_locked != 0)
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lck->l_wait(lck, lu);
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atomic_store_rel_long(&lu->lu_watchreq->lr_waiting, 0);
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/*
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* Wait for original owner to stop accessing the
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* lockreq object.
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*/
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while (lu->lu_watchreq->lr_handshake)
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;
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}
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}
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}
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@ -232,19 +240,24 @@ _lock_release(struct lock *lck, struct lockuser *lu)
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}
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}
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if (lu_h != NULL) {
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lu_h->lu_watchreq->lr_handshake = 1;
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/* Give the lock to the highest priority user. */
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atomic_store_rel_long(&lu_h->lu_watchreq->lr_locked, 0);
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if ((lu_h->lu_watchreq->lr_waiting != 0) &&
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(lck->l_wakeup != NULL))
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/* Notify the sleeper */
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lck->l_wakeup(lck, lu_h->lu_myreq->lr_watcher);
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atomic_store_rel_long(&lu_h->lu_watchreq->lr_handshake,
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0);
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} else {
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myreq->lr_handshake = 1;
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/* Give the lock to the previous request. */
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atomic_store_rel_long(&myreq->lr_locked, 0);
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if ((myreq->lr_waiting != 0) &&
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(lck->l_wakeup != NULL))
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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atomic_store_rel_long(&myreq->lr_handshake, 0);
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}
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} else {
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/*
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@ -257,12 +270,19 @@ _lock_release(struct lock *lck, struct lockuser *lu)
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lu->lu_watchreq = NULL;
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lu->lu_myreq->lr_locked = 1;
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lu->lu_myreq->lr_waiting = 0;
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/* Give the lock to the previous request. */
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atomic_store_rel_long(&myreq->lr_locked, 0);
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if ((myreq->lr_waiting != 0) &&
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(lck->l_wakeup != NULL))
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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if (lck->l_wakeup) {
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/* Start wakeup */
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myreq->lr_handshake = 1;
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/* Give the lock to the previous request. */
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atomic_store_rel_long(&myreq->lr_locked, 0);
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if (myreq->lr_waiting != 0) {
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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}
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/* Stop wakeup */
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atomic_store_rel_long(&myreq->lr_handshake, 0);
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} else {
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atomic_store_rel_long(&myreq->lr_locked, 0);
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}
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}
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}
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@ -55,6 +55,7 @@ struct lockreq {
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struct lockuser *lr_watcher; /* only used for priority locks */
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struct lockuser *lr_owner; /* only used for priority locks */
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long lr_waiting; /* non-zero when wakeup needed */
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volatile long lr_handshake; /* non-zero when wakeup in progress */
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};
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struct lockuser {
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@ -65,6 +65,7 @@ _lock_init(struct lock *lck, enum lock_type ltype,
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lck->l_head->lr_watcher = NULL;
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lck->l_head->lr_owner = NULL;
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lck->l_head->lr_waiting = 0;
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lck->l_head->lr_handshake = 0;
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lck->l_tail = lck->l_head;
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}
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return (0);
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@ -84,6 +85,7 @@ _lockuser_init(struct lockuser *lu, void *priv)
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lu->lu_myreq->lr_watcher = NULL;
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lu->lu_myreq->lr_owner = lu;
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lu->lu_myreq->lr_waiting = 0;
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lu->lu_myreq->lr_handshake = 0;
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lu->lu_watchreq = NULL;
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lu->lu_priority = 0;
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lu->lu_private = priv;
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@ -169,6 +171,12 @@ _lock_acquire(struct lock *lck, struct lockuser *lu, int prio)
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while (lu->lu_watchreq->lr_locked != 0)
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lck->l_wait(lck, lu);
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atomic_store_rel_long(&lu->lu_watchreq->lr_waiting, 0);
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/*
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* Wait for original owner to stop accessing the
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* lockreq object.
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*/
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while (lu->lu_watchreq->lr_handshake)
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;
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}
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}
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}
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@ -232,19 +240,24 @@ _lock_release(struct lock *lck, struct lockuser *lu)
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}
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}
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if (lu_h != NULL) {
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lu_h->lu_watchreq->lr_handshake = 1;
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/* Give the lock to the highest priority user. */
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atomic_store_rel_long(&lu_h->lu_watchreq->lr_locked, 0);
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if ((lu_h->lu_watchreq->lr_waiting != 0) &&
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(lck->l_wakeup != NULL))
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/* Notify the sleeper */
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lck->l_wakeup(lck, lu_h->lu_myreq->lr_watcher);
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atomic_store_rel_long(&lu_h->lu_watchreq->lr_handshake,
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0);
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} else {
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myreq->lr_handshake = 1;
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/* Give the lock to the previous request. */
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atomic_store_rel_long(&myreq->lr_locked, 0);
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if ((myreq->lr_waiting != 0) &&
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(lck->l_wakeup != NULL))
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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atomic_store_rel_long(&myreq->lr_handshake, 0);
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}
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} else {
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/*
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@ -257,12 +270,19 @@ _lock_release(struct lock *lck, struct lockuser *lu)
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lu->lu_watchreq = NULL;
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lu->lu_myreq->lr_locked = 1;
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lu->lu_myreq->lr_waiting = 0;
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/* Give the lock to the previous request. */
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atomic_store_rel_long(&myreq->lr_locked, 0);
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if ((myreq->lr_waiting != 0) &&
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(lck->l_wakeup != NULL))
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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if (lck->l_wakeup) {
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/* Start wakeup */
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myreq->lr_handshake = 1;
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/* Give the lock to the previous request. */
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atomic_store_rel_long(&myreq->lr_locked, 0);
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if (myreq->lr_waiting != 0) {
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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}
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/* Stop wakeup */
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atomic_store_rel_long(&myreq->lr_handshake, 0);
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} else {
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atomic_store_rel_long(&myreq->lr_locked, 0);
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}
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}
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}
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@ -55,6 +55,7 @@ struct lockreq {
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struct lockuser *lr_watcher; /* only used for priority locks */
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struct lockuser *lr_owner; /* only used for priority locks */
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long lr_waiting; /* non-zero when wakeup needed */
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volatile long lr_handshake; /* non-zero when wakeup in progress */
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};
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struct lockuser {
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