Changes in / [0578271:32efd86] in mainline

File:

• uspace/lib/c/generic/fibril_synch.c (modified) (4 diffs)

uspace/lib/c/generic/fibril_synch.c

@@ -180 +180 @@
 void fibril_rwlock_read_lock(fibril_rwlock_t *frw)
 {
+        fibril_t *f = (fibril_t *) fibril_get_id();
+        
         futex_down(&async_futex);
         if (frw->writers) {
-                fibril_t *f = (fibril_t *) fibril_get_id();
                 awaiter_t wdata;
 
@@ -195 +196 @@
                 fibril_switch(FIBRIL_TO_MANAGER);
         } else {
-                frw->readers++;
+                /* Consider the first reader the owner. */
+                if (frw->readers++ == 0)
+                        frw->oi.owned_by = f;
                 futex_up(&async_futex);
         }
@@ -229 +232 @@
         assert(frw->readers || (frw->writers == 1));
         if (frw->readers) {
-                if (--frw->readers)
+                if (--frw->readers) {
+                        if (frw->oi.owned_by == (fibril_t *) fibril_get_id()) {
+                                /*
+                                 * If this reader firbril was considered the
+                                 * owner of this rwlock, clear the ownership
+                                 * information even if there are still more
+                                 * readers.
+                                 *
+                                 * This is the limitation of the detection
+                                 * mechanism rooted in the fact that tracking
+                                 * all readers would require dynamically
+                                 * allocated memory for keeping linkage info.
+                                 */
+                                frw->oi.owned_by = NULL;
+                        }
                         goto out;
+                }
         } else {
                 frw->writers--;
@@ -265 +283 @@
                         list_remove(&wdp->wu_event.link);
                         fibril_add_ready(wdp->fid);
-                        frw->readers++;
+                        if (frw->readers++ == 0) {
+                                /* Consider the first reader the owner. */
+                                frw->oi.owned_by = f;
+                        }
                         optimize_execution_power();
                 }