Changes in uspace/lib/c/generic/fibril_synch.c [84b7384:9414abc] in mainline

File:

• uspace/lib/c/generic/fibril_synch.c (modified) (12 diffs)

uspace/lib/c/generic/fibril_synch.c

@@ -58 +58 @@
 }
 
-static bool check_for_deadlock(fibril_owner_info_t *oi)
-{
-        while (oi && oi->owned_by) {
-                if (oi->owned_by == (fibril_t *) fibril_get_id())
-                        return true;
-                oi = oi->owned_by->waits_for;
-        }
-
-        return false;
-}
-
 static void print_deadlock(fibril_owner_info_t *oi)
 {
@@ -89 +78 @@
                 oi = oi->owned_by->waits_for;
         }
-
-        abort();
-}
+}
+
+
+static void check_for_deadlock(fibril_owner_info_t *oi)
+{
+        while (oi && oi->owned_by) {
+                if (oi->owned_by == (fibril_t *) fibril_get_id()) {
+                        print_deadlock(oi);
+                        abort();
+                }
+                oi = oi->owned_by->waits_for;
+        }
+}
+
 
 void fibril_mutex_initialize(fibril_mutex_t *fm)
@@ -113 +113 @@
                 link_initialize(&wdata.wu_event.link);
                 list_append(&wdata.wu_event.link, &fm->waiters);
-
-                if (check_for_deadlock(&fm->oi))
-                        print_deadlock(&fm->oi);
+                check_for_deadlock(&fm->oi);
                 f->waits_for = &fm->oi;
-
                 fibril_switch(FIBRIL_TO_MANAGER);
         } else {
@@ -183 +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;
 
@@ -194 +192 @@
                 f->flags &= ~FIBRIL_WRITER;
                 list_append(&wdata.wu_event.link, &frw->waiters);
+                check_for_deadlock(&frw->oi);
+                f->waits_for = &frw->oi;
                 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);
         }
@@ -203 +205 @@
 void fibril_rwlock_write_lock(fibril_rwlock_t *frw)
 {
+        fibril_t *f = (fibril_t *) fibril_get_id();
+        
         futex_down(&async_futex);
         if (frw->writers || frw->readers) {
-                fibril_t *f = (fibril_t *) fibril_get_id();
                 awaiter_t wdata;
 
@@ -214 +217 @@
                 f->flags |= FIBRIL_WRITER;
                 list_append(&wdata.wu_event.link, &frw->waiters);
+                check_for_deadlock(&frw->oi);
+                f->waits_for = &frw->oi;
                 fibril_switch(FIBRIL_TO_MANAGER);
         } else {
+                frw->oi.owned_by = f;
                 frw->writers++;
                 futex_up(&async_futex);
@@ -226 +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--;
@@ -233 +254 @@
         
         assert(!frw->readers && !frw->writers);
+        
+        frw->oi.owned_by = NULL;
         
         while (!list_empty(&frw->waiters)) {
@@ -241 +264 @@
                 wdp = list_get_instance(tmp, awaiter_t, wu_event.link);
                 f = (fibril_t *) wdp->fid;
+                
+                f->waits_for = NULL;
                 
                 if (f->flags & FIBRIL_WRITER) {
@@ -250 +275 @@
                         fibril_add_ready(wdp->fid);
                         frw->writers++;
+                        frw->oi.owned_by = f;
                         optimize_execution_power();
                         break;
@@ -257 +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();
                 }