Changeset ab6edb6 in mainline for uspace/lib/c/generic/fibril.c

Timestamp:

2018-06-26T17:34:48Z (7 years ago)

Author:

Jiří Zárevúcky <jiri.zarevucky@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

e768aea

Parents:

b59318e

git-author:

Jiří Zárevúcky <jiri.zarevucky@…> (2018-06-25 19:28:19)

git-committer:

Jiří Zárevúcky <jiri.zarevucky@…> (2018-06-26 17:34:48)

Message:

Simplify the interaction between async_futex and fibril_switch().

File:

• uspace/lib/c/generic/fibril.c (modified) (7 diffs)

uspace/lib/c/generic/fibril.c

@@ -71 +71 @@
 static void fibril_main(void)
 {
-        /* fibril_futex is locked when a fibril is first started. */
-        futex_unlock(&fibril_futex);
+        /* fibril_futex and async_futex are locked when a fibril is started. */
+        futex_unlock(&fibril_futex);
+        futex_unlock(&async_futex);
 
         fibril_t *fibril = fibril_self();
@@ -127 +128 @@
 /** Switch from the current fibril.
  *
- * If stype is FIBRIL_TO_MANAGER or FIBRIL_FROM_DEAD, the async_futex must
- * be held.
+ * The async_futex must be held when entering this function,
+ * and is still held on return.
  *
  * @param stype Switch type. One of FIBRIL_PREEMPT, FIBRIL_TO_MANAGER,
@@ -140 +141 @@
 int fibril_switch(fibril_switch_type_t stype)
 {
+        /* Make sure the async_futex is held. */
+        futex_assert_is_locked(&async_futex);
+
         futex_lock(&fibril_futex);
 
@@ -146 +150 @@
 
         /* Choose a new fibril to run */
-        switch (stype) {
-        case FIBRIL_TO_MANAGER:
-        case FIBRIL_FROM_DEAD:
-                /* Make sure the async_futex is held. */
-                futex_assert_is_locked(&async_futex);
+        if (list_empty(&ready_list)) {
+                if (stype == FIBRIL_PREEMPT) {
+                        // FIXME: This means that as long as there is a fibril
+                        // that only yields, IPC messages are never retrieved.
+                        futex_unlock(&fibril_futex);
+                        return 0;
+                }
 
                 /* If we are going to manager and none exists, create it */
@@ -161 +167 @@
                 dstf = list_get_instance(list_first(&manager_list),
                     fibril_t, link);
-
-                /* Bookkeeping. */
-                futex_give_to(&async_futex, dstf);
-
-                if (stype == FIBRIL_FROM_DEAD)
-                        dstf->clean_after_me = srcf;
-                break;
-        case FIBRIL_PREEMPT:
-        case FIBRIL_FROM_MANAGER:
-                futex_assert_is_not_locked(&async_futex);
-
-                if (list_empty(&ready_list)) {
-                        futex_unlock(&fibril_futex);
-                        return 0;
-                }
-
+        } else {
                 dstf = list_get_instance(list_first(&ready_list), fibril_t,
                     link);
-                break;
-        }
+        }
+
         list_remove(&dstf->link);
+        if (stype == FIBRIL_FROM_DEAD)
+                dstf->clean_after_me = srcf;
 
         /* Put the current fibril into the correct run list */
@@ -192 +185 @@
                 break;
         case FIBRIL_FROM_DEAD:
+        case FIBRIL_FROM_BLOCKED:
                 // Nothing.
                 break;
-        case FIBRIL_TO_MANAGER:
-                /*
-                 * Don't put the current fibril into any list, it should
-                 * already be somewhere, or it will be lost.
-                 */
-                break;
         }
 
         /* Bookkeeping. */
         futex_give_to(&fibril_futex, dstf);
+        futex_give_to(&async_futex, dstf);
 
         /* Swap to the next fibril. */
@@ -350 +339 @@
 void fibril_yield(void)
 {
-        fibril_switch(FIBRIL_PREEMPT);
+        futex_lock(&async_futex);
+        (void) fibril_switch(FIBRIL_PREEMPT);
+        futex_unlock(&async_futex);
 }