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-rw-r--r--lib/libthr/thread/thr_exit.c6
-rw-r--r--lib/libthr/thread/thr_private.h16
-rw-r--r--lib/libthr/thread/thr_rwlock.c141
3 files changed, 155 insertions, 8 deletions
diff --git a/lib/libthr/thread/thr_exit.c b/lib/libthr/thread/thr_exit.c
index facd707..41b1f86 100644
--- a/lib/libthr/thread/thr_exit.c
+++ b/lib/libthr/thread/thr_exit.c
@@ -122,6 +122,12 @@ _pthread_exit(void *status)
_thread_cleanupspecific();
}
+ /*
+ * Remove read-write lock list. It is allocated as-needed.
+ * Therefore, it must be checked for validity before freeing.
+ */
+ if (curthread->rwlockList != NULL)
+ free(curthread->rwlockList);
retry:
/*
* Proper lock order, to minimize deadlocks, between joining
diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
index 7a7412b..c2bea3f 100644
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -423,6 +423,15 @@ struct pthread_specific_elem {
int seqno;
};
+struct rwlock_held {
+ LIST_ENTRY(rwlock_held) rh_link;
+ struct pthread_rwlock *rh_rwlock;
+ int rh_rdcount;
+ int rh_wrcount;
+};
+
+LIST_HEAD(rwlock_listhead, rwlock_held);
+
/*
* Thread structure.
*/
@@ -562,6 +571,13 @@ struct pthread {
*/
TAILQ_HEAD(, pthread_mutex) mutexq;
+ /*
+ * List of read-write locks owned for reading _OR_ writing.
+ * This is accessed only by the current thread, so there's
+ * no need for mutual exclusion.
+ */
+ struct rwlock_listhead *rwlockList;
+
void *ret;
struct pthread_specific_elem *specific;
int specific_data_count;
diff --git a/lib/libthr/thread/thr_rwlock.c b/lib/libthr/thread/thr_rwlock.c
index afd2fa5..8644e1e 100644
--- a/lib/libthr/thread/thr_rwlock.c
+++ b/lib/libthr/thread/thr_rwlock.c
@@ -37,6 +37,11 @@
/* maximum number of times a read lock may be obtained */
#define MAX_READ_LOCKS (INT_MAX - 1)
+/*
+ * For distinguishing operations on read and write locks.
+ */
+enum rwlock_type {RWT_READ, RWT_WRITE};
+
__weak_reference(_pthread_rwlock_destroy, pthread_rwlock_destroy);
__weak_reference(_pthread_rwlock_init, pthread_rwlock_init);
__weak_reference(_pthread_rwlock_rdlock, pthread_rwlock_rdlock);
@@ -47,6 +52,7 @@ __weak_reference(_pthread_rwlock_trywrlock, pthread_rwlock_trywrlock);
__weak_reference(_pthread_rwlock_unlock, pthread_rwlock_unlock);
__weak_reference(_pthread_rwlock_wrlock, pthread_rwlock_wrlock);
+static int insert_rwlock(struct pthread_rwlock *, enum rwlock_type);
static int rwlock_rdlock_common(pthread_rwlock_t *, int,
const struct timespec *);
static int rwlock_wrlock_common(pthread_rwlock_t *, int,
@@ -84,12 +90,14 @@ _pthread_rwlock_init (pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr
/* allocate rwlock object */
prwlock = (pthread_rwlock_t)malloc(sizeof(struct pthread_rwlock));
- if (prwlock == NULL)
- return(ENOMEM);
+ if (prwlock == NULL) {
+ ret = ENOMEM;
+ goto out;
+ }
/* initialize the lock */
if ((ret = pthread_mutex_init(&prwlock->lock, NULL)) != 0)
- goto out_mutex;
+ goto out;
/* initialize the read condition signal */
if ((ret = pthread_cond_init(&prwlock->read_signal, NULL)) != 0)
@@ -110,8 +118,9 @@ out_writecond:
pthread_cond_destroy(&prwlock->read_signal);
out_readcond:
pthread_mutex_destroy(&prwlock->lock);
-out_mutex:
- free(prwlock);
+out:
+ if (prwlock != NULL)
+ free(prwlock);
return(ret);
}
@@ -123,9 +132,11 @@ static int
rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking,
const struct timespec *timeout)
{
+ struct rwlock_held *rh;
pthread_rwlock_t prwlock;
int ret;
+ rh = NULL;
if (rwlock == NULL || *rwlock == NULL)
return(EINVAL);
@@ -155,6 +166,19 @@ rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking,
return (EBUSY);
}
+ /*
+ * If this lock is already held for writing we have
+ * a deadlock situation.
+ */
+ if (curthread->rwlockList != NULL && prwlock->state < 0) {
+ LIST_FOREACH(rh, curthread->rwlockList, rh_link) {
+ if (rh->rh_rwlock == prwlock &&
+ rh->rh_wrcount > 0) {
+ pthread_mutex_unlock(&prwlock->lock);
+ return (EDEADLK);
+ }
+ }
+ }
if (timeout == NULL)
ret = pthread_cond_wait(&prwlock->read_signal,
&prwlock->lock);
@@ -170,6 +194,11 @@ rwlock_rdlock_common(pthread_rwlock_t *rwlock, int nonblocking,
}
++prwlock->state; /* indicate we are locked for reading */
+ ret = insert_rwlock(prwlock, RWT_READ);
+ if (ret != 0) {
+ pthread_mutex_unlock(&prwlock->lock);
+ return (ret);
+ }
/*
* Something is really wrong if this call fails. Returning
@@ -204,9 +233,11 @@ _pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
int
_pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
{
+ struct rwlock_held *rh;
pthread_rwlock_t prwlock;
int ret;
+ rh = NULL;
if (rwlock == NULL || *rwlock == NULL)
return(EINVAL);
@@ -216,20 +247,45 @@ _pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
if ((ret = pthread_mutex_lock(&prwlock->lock)) != 0)
return(ret);
- /* XXX - Make sure we hold a lock on this rwlock */
-
+ if (curthread->rwlockList != NULL) {
+ LIST_FOREACH(rh, curthread->rwlockList, rh_link) {
+ if (rh->rh_rwlock == prwlock)
+ break;
+ }
+ }
+ if (rh == NULL) {
+ ret = EPERM;
+ goto out;
+ }
if (prwlock->state > 0) {
+ rh->rh_rdcount--;
+ if (rh->rh_rdcount == 0) {
+ LIST_REMOVE(rh, rh_link);
+ free(rh);
+ }
if (--prwlock->state == 0 && prwlock->blocked_writers)
ret = pthread_cond_signal(&prwlock->write_signal);
} else if (prwlock->state < 0) {
+ rh->rh_wrcount--;
+ if (rh->rh_wrcount == 0) {
+ LIST_REMOVE(rh, rh_link);
+ free(rh);
+ }
prwlock->state = 0;
-
if (prwlock->blocked_writers)
ret = pthread_cond_signal(&prwlock->write_signal);
else
ret = pthread_cond_broadcast(&prwlock->read_signal);
+ } else {
+ /*
+ * No thread holds this lock. We should never get here.
+ */
+ PTHREAD_ASSERT(0, "state=0 on read-write lock held by thread");
+ ret = EPERM;
+ goto out;
}
+out:
/* see the comment on this in rwlock_rdlock_common */
pthread_mutex_unlock(&prwlock->lock);
@@ -263,9 +319,11 @@ static int
rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking,
const struct timespec *timeout)
{
+ struct rwlock_held *rh;
pthread_rwlock_t prwlock;
int ret;
+ rh = NULL;
if (rwlock == NULL || *rwlock == NULL)
return(EINVAL);
@@ -288,6 +346,21 @@ rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking,
return (EBUSY);
}
+ /*
+ * If this thread already holds the lock for reading
+ * or writing we have a deadlock situation.
+ */
+ if (curthread->rwlockList != NULL) {
+ LIST_FOREACH(rh, curthread->rwlockList, rh_link) {
+ if (rh->rh_rwlock == prwlock &&
+ (rh->rh_rdcount > 0 || rh->rh_wrcount > 0)) {
+ pthread_mutex_unlock(&prwlock->lock);
+ return (EDEADLK);
+ break;
+ }
+ }
+ }
+
++prwlock->blocked_writers;
if (timeout == NULL)
@@ -308,6 +381,11 @@ rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking,
/* indicate we are locked for writing */
prwlock->state = -1;
+ ret = insert_rwlock(prwlock, RWT_WRITE);
+ if (ret != 0) {
+ pthread_mutex_unlock(&prwlock->lock);
+ return (ret);
+ }
/* see the comment on this in pthread_rwlock_rdlock */
pthread_mutex_unlock(&prwlock->lock);
@@ -315,3 +393,50 @@ rwlock_wrlock_common(pthread_rwlock_t *rwlock, int nonblocking,
return(0);
}
+static int
+insert_rwlock(struct pthread_rwlock *prwlock, enum rwlock_type rwt)
+{
+ struct rwlock_held *rh;
+
+ /*
+ * Initialize the rwlock list in the thread. Although this function
+ * may be called for many read-write locks, the initialization
+ * of the the head happens only once during the lifetime of
+ * the thread.
+ */
+ if (curthread->rwlockList == NULL) {
+ curthread->rwlockList =
+ (struct rwlock_listhead *)malloc(sizeof(struct rwlock_listhead));
+ if (curthread->rwlockList == NULL) {
+ return (ENOMEM);
+ }
+ LIST_INIT(curthread->rwlockList);
+ }
+
+ LIST_FOREACH(rh, curthread->rwlockList, rh_link) {
+ if (rh->rh_rwlock == prwlock) {
+ if (rwt == RWT_READ)
+ rh->rh_rdcount++;
+ else if (rwt == RWT_WRITE)
+ rh->rh_wrcount++;
+ return (0);
+ }
+ }
+
+ /*
+ * This is the first time we're holding this lock,
+ * create a new entry.
+ */
+ rh = (struct rwlock_held *)malloc(sizeof(struct rwlock_held));
+ if (rh == NULL)
+ return (ENOMEM);
+ rh->rh_rwlock = prwlock;
+ rh->rh_rdcount = 0;
+ rh->rh_wrcount = 0;
+ if (rwt == RWT_READ)
+ rh->rh_rdcount = 1;
+ else if (rwt == RWT_WRITE)
+ rh->rh_wrcount = 1;
+ LIST_INSERT_HEAD(curthread->rwlockList, rh, rh_link);
+ return (0);
+}
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