d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Protect against a race between granting a lock and accessing

Browse Source 
other parts of the lock.

Submitted by:	davidxu
This commit is contained in:
deischen 2003-05-04 22:29:09 +00:00
parent 9328ad6bf8
commit 3cb9ba9e43
4 changed files with 56 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
lib/libkse/sys/lock.c
View File

@ -65,6 +65,7 @@ _lock_init(struct lock *lck, enum lock_type ltype,
lck->l_head->lr_watcher = NULL;
lck->l_head->lr_owner = NULL;
lck->l_head->lr_waiting = 0;
lck->l_head->lr_handshake = 0;
lck->l_tail = lck->l_head;
}
return (0);
@ -84,6 +85,7 @@ _lockuser_init(struct lockuser *lu, void *priv)
lu->lu_myreq->lr_watcher = NULL;
lu->lu_myreq->lr_owner = lu;
lu->lu_myreq->lr_waiting = 0;
lu->lu_myreq->lr_handshake = 0;
lu->lu_watchreq = NULL;
lu->lu_priority = 0;
lu->lu_private = priv;
@ -169,6 +171,12 @@ _lock_acquire(struct lock *lck, struct lockuser *lu, int prio)
while (lu->lu_watchreq->lr_locked != 0)
lck->l_wait(lck, lu);
atomic_store_rel_long(&lu->lu_watchreq->lr_waiting, 0);
/*
* Wait for original owner to stop accessing the
* lockreq object.
*/
while (lu->lu_watchreq->lr_handshake)
;
}
}
}
@ -232,19 +240,24 @@ _lock_release(struct lock *lck, struct lockuser *lu)
}
}
if (lu_h != NULL) {
lu_h->lu_watchreq->lr_handshake = 1;
/* Give the lock to the highest priority user. */
atomic_store_rel_long(&lu_h->lu_watchreq->lr_locked, 0);
if ((lu_h->lu_watchreq->lr_waiting != 0) &&
(lck->l_wakeup != NULL))
/* Notify the sleeper */
lck->l_wakeup(lck, lu_h->lu_myreq->lr_watcher);
atomic_store_rel_long(&lu_h->lu_watchreq->lr_handshake,
0);
} else {
myreq->lr_handshake = 1;
/* Give the lock to the previous request. */
atomic_store_rel_long(&myreq->lr_locked, 0);
if ((myreq->lr_waiting != 0) &&
(lck->l_wakeup != NULL))
/* Notify the sleeper */
lck->l_wakeup(lck, myreq->lr_watcher);
atomic_store_rel_long(&myreq->lr_handshake, 0);
}
} else {
/*
@ -257,12 +270,19 @@ _lock_release(struct lock *lck, struct lockuser *lu)
lu->lu_watchreq = NULL;
lu->lu_myreq->lr_locked = 1;
lu->lu_myreq->lr_waiting = 0;
/* Give the lock to the previous request. */
atomic_store_rel_long(&myreq->lr_locked, 0);
if ((myreq->lr_waiting != 0) &&
(lck->l_wakeup != NULL))
/* Notify the sleeper */
lck->l_wakeup(lck, myreq->lr_watcher);
if (lck->l_wakeup) {
/* Start wakeup */
myreq->lr_handshake = 1;
/* Give the lock to the previous request. */
atomic_store_rel_long(&myreq->lr_locked, 0);
if (myreq->lr_waiting != 0) {
/* Notify the sleeper */
lck->l_wakeup(lck, myreq->lr_watcher);
}
/* Stop wakeup */
atomic_store_rel_long(&myreq->lr_handshake, 0);
} else {
atomic_store_rel_long(&myreq->lr_locked, 0);
}
}
}

1
lib/libkse/sys/lock.h
View File

@ -55,6 +55,7 @@ struct lockreq {
struct lockuser *lr_watcher; /* only used for priority locks */
struct lockuser *lr_owner; /* only used for priority locks */
long lr_waiting; /* non-zero when wakeup needed */
volatile long lr_handshake; /* non-zero when wakeup in progress */
};
struct lockuser {

34
lib/libpthread/sys/lock.c
View File

@ -65,6 +65,7 @@ _lock_init(struct lock *lck, enum lock_type ltype,
lck->l_head->lr_watcher = NULL;
lck->l_head->lr_owner = NULL;
lck->l_head->lr_waiting = 0;
lck->l_head->lr_handshake = 0;
lck->l_tail = lck->l_head;
}
return (0);
@ -84,6 +85,7 @@ _lockuser_init(struct lockuser *lu, void *priv)
lu->lu_myreq->lr_watcher = NULL;
lu->lu_myreq->lr_owner = lu;
lu->lu_myreq->lr_waiting = 0;
lu->lu_myreq->lr_handshake = 0;
lu->lu_watchreq = NULL;
lu->lu_priority = 0;
lu->lu_private = priv;
@ -169,6 +171,12 @@ _lock_acquire(struct lock *lck, struct lockuser *lu, int prio)
while (lu->lu_watchreq->lr_locked != 0)
lck->l_wait(lck, lu);
atomic_store_rel_long(&lu->lu_watchreq->lr_waiting, 0);
/*
* Wait for original owner to stop accessing the
* lockreq object.
*/
while (lu->lu_watchreq->lr_handshake)
;
}
}
}
@ -232,19 +240,24 @@ _lock_release(struct lock *lck, struct lockuser *lu)
}
}
if (lu_h != NULL) {
lu_h->lu_watchreq->lr_handshake = 1;
/* Give the lock to the highest priority user. */
atomic_store_rel_long(&lu_h->lu_watchreq->lr_locked, 0);
if ((lu_h->lu_watchreq->lr_waiting != 0) &&
(lck->l_wakeup != NULL))
/* Notify the sleeper */
lck->l_wakeup(lck, lu_h->lu_myreq->lr_watcher);
atomic_store_rel_long(&lu_h->lu_watchreq->lr_handshake,
0);
} else {
myreq->lr_handshake = 1;
/* Give the lock to the previous request. */
atomic_store_rel_long(&myreq->lr_locked, 0);
if ((myreq->lr_waiting != 0) &&
(lck->l_wakeup != NULL))
/* Notify the sleeper */
lck->l_wakeup(lck, myreq->lr_watcher);
atomic_store_rel_long(&myreq->lr_handshake, 0);
}
} else {
/*
@ -257,12 +270,19 @@ _lock_release(struct lock *lck, struct lockuser *lu)
lu->lu_watchreq = NULL;
lu->lu_myreq->lr_locked = 1;
lu->lu_myreq->lr_waiting = 0;
/* Give the lock to the previous request. */
atomic_store_rel_long(&myreq->lr_locked, 0);
if ((myreq->lr_waiting != 0) &&
(lck->l_wakeup != NULL))
/* Notify the sleeper */
lck->l_wakeup(lck, myreq->lr_watcher);
if (lck->l_wakeup) {
/* Start wakeup */
myreq->lr_handshake = 1;
/* Give the lock to the previous request. */
atomic_store_rel_long(&myreq->lr_locked, 0);
if (myreq->lr_waiting != 0) {
/* Notify the sleeper */
lck->l_wakeup(lck, myreq->lr_watcher);
}
/* Stop wakeup */
atomic_store_rel_long(&myreq->lr_handshake, 0);
} else {
atomic_store_rel_long(&myreq->lr_locked, 0);
}
}
}

1
lib/libpthread/sys/lock.h
View File

@ -55,6 +55,7 @@ struct lockreq {
struct lockuser *lr_watcher; /* only used for priority locks */
struct lockuser *lr_owner; /* only used for priority locks */
long lr_waiting; /* non-zero when wakeup needed */
volatile long lr_handshake; /* non-zero when wakeup in progress */
};
struct lockuser {