rework the logic of pa_asyncq

git-svn-id: file:///home/lennart/svn/public/pulseaudio/branches/lennart@1496 fefdeb5f-60dc-0310-8127-8f9354f1896f

diff --git a/src/pulsecore/asyncq.c b/src/pulsecore/asyncq.c
index c966e7dd04653633f7a3350accb2950805bfb444..025c695e533a116f24298d9a18da746b3d68d73d 100644 (file)
--- a/src/pulsecore/asyncq.c
+++ b/src/pulsecore/asyncq.c
@@ -52,9 +52,10 @@ struct pa_asyncq {
     unsigned size;
     unsigned read_idx;
     unsigned write_idx;
-    pa_atomic_t read_waiting, n_read;
-    pa_atomic_t write_waiting, n_written;
+    pa_atomic_t read_waiting; /* a bool */
+    pa_atomic_t write_waiting; /* a bool */
     int read_fds[2], write_fds[2];
+    pa_atomic_t in_read_fifo, in_write_fifo;
 };
 
 #define PA_ASYNCQ_CELLS(x) ((pa_atomic_ptr_t*) ((uint8_t*) (x) + PA_ALIGN(sizeof(struct pa_asyncq))))
@@ -80,8 +81,8 @@ pa_asyncq *pa_asyncq_new(unsigned size) {
     l->size = size;
     pa_atomic_store(&l->read_waiting, 0);
     pa_atomic_store(&l->write_waiting, 0);
-    pa_atomic_store(&l->n_written, 0);
-    pa_atomic_store(&l->n_read, 0);
+    pa_atomic_store(&l->in_read_fifo, 0);
+    pa_atomic_store(&l->in_write_fifo, 0);
 
     if (pipe(l->read_fds) < 0) {
         pa_xfree(l);
@@ -133,68 +134,79 @@ int pa_asyncq_push(pa_asyncq*l, void *p, int wait) {
 
     if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) {
 
-        if (!wait) {
-            /* Let's empty the FIFO from old notifications, before we return */
+        /* Let's empty the FIFO from old notifications, before we return */
             
-            while (pa_atomic_load(&l->n_read) > 0) {
-                ssize_t r;
-                int x[20];
-                
-                errno = 0;
-                if ((r = read(l->write_fds[0], x, sizeof(x))) < 0 && errno != EINTR)
-                    return -1;
+        while (pa_atomic_load(&l->in_write_fifo) > 0) {
+            ssize_t r;
+            int x[20];
+
+            if ((r = read(l->write_fds[0], x, sizeof(x))) < 0) {
 
-                pa_assert(r != 0);
+                if (errno == EINTR)
+                    continue;
                 
-                if (r > 0)
-                    if (pa_atomic_sub(&l->n_read, r) <= r)
-                        break;
+                return -1;
             }
-            
-            return -1;
-        }
-
-        /* First try failed. Let's wait for changes. */
 
-        _Y;
+            pa_assert(r > 0);
+                
+            if (pa_atomic_sub(&l->in_write_fifo, r) <= r)
+                break;
 
-        pa_atomic_inc(&l->write_waiting);
+        }
 
-        for (;;) {
-            char x[20];
-            ssize_t r;
+        /* Now let's make sure that we didn't lose any events */
+        if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) {
 
-            _Y;
+            if (!wait)
+                return -1;
 
-            if (pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p))
-                break;
+            /* Let's wait for changes. */
 
             _Y;
 
-            if ((r = read(l->write_fds[0], x, sizeof(x))) < 0 && errno != EINTR) {
-                pa_atomic_dec(&l->write_waiting);
-                return -1;
-            }
+            pa_assert_se(pa_atomic_cmpxchg(&l->write_waiting, 0, 1));
 
-            pa_assert(r != 0);
+            for (;;) {
+                char x[20];
+                ssize_t r;
+                
+                _Y;
+                
+                if (pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p))
+                    break;
+                
+                _Y;
 
-            if (r > 0)
-                pa_atomic_sub(&l->n_read, r);
-        }
+                if ((r = read(l->write_fds[0], x, sizeof(x))) < 0) {
 
-        _Y;
+                    if (errno == EINTR)
+                        continue;
+                    
+                    pa_assert_se(pa_atomic_cmpxchg(&l->write_waiting, 1, 0));
+                    return -1;
+                }
 
-        pa_atomic_dec(&l->write_waiting);
+                pa_assert(r > 0);
+                pa_atomic_sub(&l->in_write_fifo, r);
+            }
+            
+            _Y;
+            
+            pa_assert_se(pa_atomic_cmpxchg(&l->write_waiting, 1, 0));
+        }
     }
 
     _Y;
     l->write_idx++;
 
-    if (pa_atomic_load(&l->read_waiting)) {
+    if (pa_atomic_load(&l->read_waiting) > 0) {
         char x = 'x';
         _Y;
-        if (write(l->read_fds[1], &x, sizeof(x)) > 0)
-            pa_atomic_inc(&l->n_written);
+        if (write(l->read_fds[1], &x, sizeof(x)) > 0) {
+            pa_atomic_inc(&l->in_read_fifo);
+/*             pa_log("increasing %p by 1", l); */
+        }
     }
 
     return 0;
@@ -206,7 +218,7 @@ void* pa_asyncq_pop(pa_asyncq*l, int wait) {
     pa_atomic_ptr_t *cells;
 
     pa_assert(l);
-
+    
     cells = PA_ASYNCQ_CELLS(l);
 
     _Y;
@@ -214,71 +226,86 @@ void* pa_asyncq_pop(pa_asyncq*l, int wait) {
 
     if (!(ret = pa_atomic_ptr_load(&cells[idx]))) {
 
-        /* First try failed. Let's wait for changes. */
+/*         pa_log("pop failed wait=%i", wait); */
 
-        if (!wait) {
-            /* Let's empty the FIFO from old notifications, before we return */
+        /* Hmm, nothing, here, so let's drop all queued events. */
+        while (pa_atomic_load(&l->in_read_fifo) > 0) {
+            ssize_t r;
+            int x[20];
             
-            while (pa_atomic_load(&l->n_written) > 0) {
-                ssize_t r;
-                int x[20];
+            if ((r = read(l->read_fds[0], x, sizeof(x))) < 0) {
                 
-                errno = 0;
-                if ((r = read(l->read_fds[0], x, sizeof(x))) < 0 && errno != EINTR)
-                    return NULL;
-
-                pa_assert(r != 0);
+                if (errno == EINTR)
+                    continue;
                 
-                if (r > 0)
-                    if (pa_atomic_sub(&l->n_written, r) <= r)
-                        break;
+                return NULL;
             }
+
+            pa_assert(r > 0);
+
+/*             pa_log("decreasing %p by %i", l, r); */
             
-            return NULL;
+            if (pa_atomic_sub(&l->in_read_fifo, r) <= r)
+                break;
         }
 
-        _Y;
-
-        pa_atomic_inc(&l->read_waiting);
+        /* Now let's make sure that we didn't lose any events */
+        if (!(ret = pa_atomic_ptr_load(&cells[idx]))) {
 
-        for (;;) {
-            char x[20];
-            ssize_t r;
+            if (!wait)
+                return NULL;
 
+            /* Let's wait for changes. */
+            
             _Y;
+            
+            pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 0, 1));
+            
+            for (;;) {
+                char x[20];
+                ssize_t r;
+                
+                _Y;
+                
+                if ((ret = pa_atomic_ptr_load(&cells[idx])))
+                    break;
+                
+                _Y;
+                
+                if ((r = read(l->read_fds[0], x, sizeof(x))) < 0) {
 
-            if ((ret = pa_atomic_ptr_load(&cells[idx])))
-                break;
-
-            _Y;
+                    if (errno == EINTR)
+                        continue;
+                    
+                    pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0));
+                    return NULL;
+                }
 
-            if ((r = read(l->read_fds[0], x, sizeof(x))) < 0 && errno != EINTR) {
-                pa_atomic_dec(&l->read_waiting);
-                return NULL;
+/*                 pa_log("decreasing %p by %i", l, r); */
+                
+                pa_assert(r > 0);
+                pa_atomic_sub(&l->in_read_fifo, r);
             }
 
-            pa_assert(r != 0);
+            _Y;
 
-            if (r > 0)
-                pa_atomic_sub(&l->n_written, r);
+            pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0));
         }
-
-        _Y;
-
-        pa_atomic_dec(&l->read_waiting);
     }
 
+    pa_assert(ret);
+
     /* Guaranteed if we only have a single reader */
     pa_assert_se(pa_atomic_ptr_cmpxchg(&cells[idx], ret, NULL));
 
     _Y;
     l->read_idx++;
 
-    if (pa_atomic_load(&l->write_waiting)) {
+    if (pa_atomic_load(&l->write_waiting) > 0) {
         char x = 'x';
         _Y;
         if (write(l->write_fds[1], &x, sizeof(x)) >= 0)
-            pa_atomic_inc(&l->n_read);
+            pa_atomic_inc(&l->in_write_fifo);
     }
 
     return ret;
@@ -301,13 +328,13 @@ int pa_asyncq_before_poll(pa_asyncq *l) {
     _Y;
     idx = reduce(l, l->read_idx);
 
-    if (pa_atomic_ptr_load(&cells[idx]))
+    if (pa_atomic_ptr_load(&cells[idx]) || pa_atomic_load(&l->in_read_fifo) > 0)
         return -1;
 
-    pa_atomic_inc(&l->read_waiting);
+    pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 0, 1));
 
-    if (pa_atomic_ptr_load(&cells[idx])) {
-        pa_atomic_dec(&l->read_waiting);
+    if (pa_atomic_ptr_load(&cells[idx]) || pa_atomic_load(&l->in_read_fifo) > 0) {
+        pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0));
         return -1;
     }
 
@@ -317,7 +344,5 @@ int pa_asyncq_before_poll(pa_asyncq *l) {
 void pa_asyncq_after_poll(pa_asyncq *l) {
     pa_assert(l);
 
-    pa_assert(pa_atomic_load(&l->read_waiting) > 0);
-
-    pa_atomic_dec(&l->read_waiting);
+    pa_assert_se(pa_atomic_cmpxchg(&l->read_waiting, 1, 0));
 }