ao_write: Avoid pthread_join().

The call to pthread_join() may block for hundreds of milliseconds,
depending of the amount of buffered data. This is not acceptable in
a post_select hook. Among other problems this leads to an incorrect time
display and fake "time jump" warnings.

This patch drops the call to pthread_join() and makes ->post_select()
return non-negative until the play thread has terminated. In order to
have a way to tell if the thread is still running we let the thread
(i.e. aow_play()) remove its own buffer tree node on exit instead
of doing this in ->post_select() after pthread_join(). Hence if
->thread_btrn is NULL, we know the thread has terminated. It would
be easier to use pthread_tryjoin_np() but this would not be portable,
as this function is a non-standard GNU extension.

diff --git a/ao_write.c b/ao_write.c
index fc65af60b3ca06735474e95c89de25387c1c9702..a2e86ed258c5857ff10014ea99d1335009e2a97b 100644 (file)
--- a/ao_write.c
+++ b/ao_write.c
@@ -51,23 +51,34 @@ static void aow_pre_select(struct sched *s, struct task *t)
        struct private_aow_data *pawd = wn->private_data;
        int ret;
 
-       if (pawd)
-               pthread_mutex_lock(&pawd->mutex);
-       ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
-       if (pawd)
-               pthread_mutex_unlock(&pawd->mutex);
-
-       if (ret == 0) {
-               /*
-                * Even though the node status is zero, we might have data
-                * available, but the output buffer is full. If we don't set a
-                * timeout here, we are woken up only if new data arrives,
-                * which might be too late and result in a buffer underrun in
-                * the playing thread. To avoid this we never sleep longer than
-                * the (default) buffer time.
-                */
-               return sched_request_timeout_ms(20, s);
+       if (!pawd) { /* not yet started */
+               assert(wn->btrn);
+               ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
+               if (ret != 0)
+                       goto min_delay;
+               return; /* no data available */
        }
+       if (!wn->btrn) { /* EOF */
+               if (!pawd->thread_btrn) /* ready to exit */
+                       goto min_delay;
+               /* wait for the play thread to terminate */
+               goto timeout;
+       }
+       pthread_mutex_lock(&pawd->mutex);
+       ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
+       pthread_mutex_unlock(&pawd->mutex);
+       if (ret != 0)
+               goto min_delay;
+       /*
+        * Even though the node status is zero, we might have data available,
+        * but the output buffer is full. If we don't set a timeout here, we
+        * are woken up only if new data arrives, which might be too late and
+        * result in a buffer underrun in the playing thread. To avoid this we
+        * never sleep longer than the (default) buffer time.
+        */
+timeout:
+       return sched_request_timeout_ms(20, s);
+min_delay:
        sched_min_delay(s);
 }
 
@@ -248,6 +259,7 @@ unlock:
 out:
        assert(ret < 0);
        PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
+       btr_remove_node(&pawd->thread_btrn);
        pthread_exit(NULL);
 }
 
@@ -332,6 +344,12 @@ static int aow_post_select(__a_unused struct sched *s,
                        goto remove_thread_btrn;
                return 0;
        }
+       if (!wn->btrn) {
+               if (!pawd->thread_btrn)
+                       return -E_AO_EOF;
+               PARA_INFO_LOG("waiting for play thread to terminate\n");
+               return 0;
+       }
        pthread_mutex_lock(&pawd->mutex);
        ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
        if (ret > 0) {
@@ -343,10 +361,9 @@ static int aow_post_select(__a_unused struct sched *s,
                goto out;
        pthread_mutex_lock(&pawd->mutex);
        btr_remove_node(&wn->btrn);
-       PARA_INFO_LOG("waiting for thread to terminate\n");
        pthread_cond_signal(&pawd->data_available);
        pthread_mutex_unlock(&pawd->mutex);
-       pthread_join(pawd->thread, NULL);
+       return 0;
 remove_thread_btrn:
        btr_remove_node(&pawd->thread_btrn);
 remove_btrn:

diff --git a/error.h b/error.h
index 301e2ca5e1ae36a045a044d8f69c072e82c62a88..ba8409dfff4e42375629ba50f8a99281ac1aa574 100644 (file)
--- a/error.h
+++ b/error.h
@@ -181,6 +181,7 @@ extern const char **para_errlist[];
        PARA_ERROR(AO_PLAY, "ao_play() failed"), \
        PARA_ERROR(AO_BAD_SAMPLE_FORMAT, "ao: unsigned sample formats not supported"), \
        PARA_ERROR(AO_PTHREAD, "pthread error"), \
+       PARA_ERROR(AO_EOF, "ao: end of file"), \
 
 
 #define COMPRESS_FILTER_ERRORS \