Use pthread condition variables instead of semaphores

[wimlib] / src / write.c

diff --git a/src/write.c b/src/write.c
index 773de0b7b6553e61ead5ef8b726e00f218b54f6a..5b586ceea23f8795cff7c28623ce2ff573df59a1 100644 (file)
--- a/src/write.c
+++ b/src/write.c
@@ -25,6 +25,15 @@
  * along with wimlib; if not, see http://www.gnu.org/licenses/.
  */
 
+#include "config.h"
+
+#if defined(HAVE_SYS_FILE_H) && defined(HAVE_FLOCK)
+/* On BSD, this should be included before "list.h" so that "list.h" can
+ * overwrite the LIST_HEAD macro. */
+#include <sys/file.h>
+#endif
+
+#include "list.h"
 #include "wimlib_internal.h"
 #include "io.h"
 #include "dentry.h"
@@ -32,13 +41,12 @@
 #include "xml.h"
 #include "lzx.h"
 #include "xpress.h"
-#include <unistd.h>
 
 #ifdef ENABLE_MULTITHREADED_COMPRESSION
-#include <semaphore.h>
 #include <pthread.h>
 #endif
 
+#include <unistd.h>
 #include <errno.h>
 
 #ifdef WITH_NTFS_3G
@@ -48,17 +56,12 @@
 #include <ntfs-3g/dir.h>
 #endif
 
-
 #ifdef HAVE_ALLOCA_H
 #include <alloca.h>
 #else
 #include <stdlib.h>
 #endif
 
-#if defined(HAVE_SYS_FILE_H) && defined(HAVE_FLOCK)
-#include <sys/file.h>
-#endif
-
 
 static int do_fflush(FILE *fp)
 {
@@ -543,13 +546,14 @@ out:
 
 #ifdef ENABLE_MULTITHREADED_COMPRESSION
 struct shared_queue {
-       sem_t filled_slots;
-       sem_t empty_slots;
-       pthread_mutex_t lock;
+       unsigned size;
        unsigned front;
        unsigned back;
+       unsigned filled_slots;
        void **array;
-       unsigned size;
+       pthread_mutex_t lock;
+       pthread_cond_t msg_avail_cond;
+       pthread_cond_t space_avail_cond;
 };
 
 static int shared_queue_init(struct shared_queue *q, unsigned size)
@@ -557,46 +561,52 @@ static int shared_queue_init(struct shared_queue *q, unsigned size)
        q->array = CALLOC(sizeof(q->array[0]), size);
        if (!q->array)
                return WIMLIB_ERR_NOMEM;
-
-       sem_init(&q->filled_slots, 0, 0);
-       sem_init(&q->empty_slots, 0, size);
-       pthread_mutex_init(&q->lock, NULL);
+       q->filled_slots = 0;
        q->front = 0;
        q->back = size - 1;
        q->size = size;
+       pthread_mutex_init(&q->lock, NULL);
+       pthread_cond_init(&q->msg_avail_cond, NULL);
+       pthread_cond_init(&q->space_avail_cond, NULL);
        return 0;
 }
 
 static void shared_queue_destroy(struct shared_queue *q)
 {
-       sem_destroy(&q->filled_slots);
-       sem_destroy(&q->empty_slots);
-       pthread_mutex_destroy(&q->lock);
        FREE(q->array);
+       pthread_mutex_destroy(&q->lock);
+       pthread_cond_destroy(&q->msg_avail_cond);
+       pthread_cond_destroy(&q->space_avail_cond);
 }
 
 static void shared_queue_put(struct shared_queue *q, void *obj)
 {
-       sem_wait(&q->empty_slots);
        pthread_mutex_lock(&q->lock);
+       while (q->filled_slots == q->size)
+               pthread_cond_wait(&q->space_avail_cond, &q->lock);
 
        q->back = (q->back + 1) % q->size;
        q->array[q->back] = obj;
+       q->filled_slots++;
 
-       sem_post(&q->filled_slots);
+       pthread_cond_broadcast(&q->msg_avail_cond);
        pthread_mutex_unlock(&q->lock);
 }
 
 static void *shared_queue_get(struct shared_queue *q)
 {
-       sem_wait(&q->filled_slots);
+       void *obj;
+
        pthread_mutex_lock(&q->lock);
+       while (q->filled_slots == 0)
+               pthread_cond_wait(&q->msg_avail_cond, &q->lock);
 
-       void *obj = q->array[q->front];
+       obj = q->array[q->front];
        q->array[q->front] = NULL;
        q->front = (q->front + 1) % q->size;
+       q->filled_slots--;
 
-       sem_post(&q->empty_slots);
+       pthread_cond_broadcast(&q->space_avail_cond);
        pthread_mutex_unlock(&q->lock);
        return obj;
 }
@@ -1492,6 +1502,29 @@ out:
        return ret;
 }
 
+#if defined(HAVE_SYS_FILE_H) && defined(HAVE_FLOCK)
+int lock_wim(FILE *fp, const char *path)
+{
+       int ret = 0;
+       if (fp) {
+               ret = flock(fileno(fp), LOCK_EX | LOCK_NB);
+               if (ret != 0) {
+                       if (errno == EWOULDBLOCK) {
+                               ERROR("`%s' is already being modified or has been "
+                                     "mounted read-write\n"
+                                     "        by another process!", path);
+                               ret = WIMLIB_ERR_ALREADY_LOCKED;
+                       } else {
+                               WARNING("Failed to lock `%s': %s",
+                                       path, strerror(errno));
+                               ret = 0;
+                       }
+               }
+       }
+       return ret;
+}
+#endif
+
 static int open_wim_writable(WIMStruct *w, const char *path,
                             bool trunc, bool readable)
 {
@@ -1513,24 +1546,13 @@ static int open_wim_writable(WIMStruct *w, const char *path,
                ERROR_WITH_ERRNO("Failed to open `%s' for writing", path);
                return WIMLIB_ERR_OPEN;
        }
-#if defined(HAVE_SYS_FILE_H) && defined(HAVE_FLOCK)
-       if (!trunc) {
-               ret = flock(fileno(w->out_fp), LOCK_EX | LOCK_NB);
+       if (trunc) {
+               ret = lock_wim(w->out_fp, path);
                if (ret != 0) {
-                       if (errno == EWOULDBLOCK) {
-                               ERROR("`%s' is already being modified "
-                                     "by another process", path);
-                               ret = WIMLIB_ERR_ALREADY_LOCKED;
-                               fclose(w->out_fp);
-                               w->out_fp = NULL;
-                       } else {
-                               WARNING("Failed to lock `%s': %s",
-                                       path, strerror(errno));
-                               ret = 0;
-                       }
+                       fclose(w->out_fp);
+                       w->out_fp = NULL;
                }
        }
-#endif
        return ret;
 }