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

Timestamp:

2018-06-26T17:34:48Z (6 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_synch.c (modified) (5 diffs)

uspace/lib/c/generic/fibril_synch.c

@@ -116 +116 @@
                 check_for_deadlock(&fm->oi);
                 f->waits_for = &fm->oi;
-                fibril_switch(FIBRIL_TO_MANAGER);
+                fibril_switch(FIBRIL_FROM_BLOCKED);
         } else {
                 fm->oi.owned_by = f;
-                futex_unlock(&async_futex);
-        }
+        }
+        futex_unlock(&async_futex);
 }
 
@@ -206 +206 @@
                 check_for_deadlock(&frw->oi);
                 f->waits_for = &frw->oi;
-                fibril_switch(FIBRIL_TO_MANAGER);
+                fibril_switch(FIBRIL_FROM_BLOCKED);
         } else {
                 /* Consider the first reader the owner. */
                 if (frw->readers++ == 0)
                         frw->oi.owned_by = f;
-                futex_unlock(&async_futex);
-        }
+        }
+        futex_unlock(&async_futex);
 }
 
@@ -230 +230 @@
                 check_for_deadlock(&frw->oi);
                 f->waits_for = &frw->oi;
-                fibril_switch(FIBRIL_TO_MANAGER);
+                fibril_switch(FIBRIL_FROM_BLOCKED);
         } else {
                 frw->oi.owned_by = f;
                 frw->writers++;
-                futex_unlock(&async_futex);
-        }
+        }
+        futex_unlock(&async_futex);
 }
 
@@ -377 +377 @@
         list_append(&wdata.wu_event.link, &fcv->waiters);
         _fibril_mutex_unlock_unsafe(fm);
-        fibril_switch(FIBRIL_TO_MANAGER);
+        fibril_switch(FIBRIL_FROM_BLOCKED);
+        futex_unlock(&async_futex);
+
+        // XXX: This could be replaced with an unlocked version to get rid
+        // of the unlock-lock pair. I deliberately don't do that because
+        // further changes would most likely need to revert that optimization.
         fibril_mutex_lock(fm);
 
-        /* async_futex not held after fibril_switch() */
         futex_lock(&async_futex);
         if (wdata.to_event.inlist)
@@ -698 +702 @@
         wdata.fid = fibril_get_id();
         list_append(&wdata.wu_event.link, &sem->waiters);
-        fibril_switch(FIBRIL_TO_MANAGER);
-
-        /* async_futex not held after fibril_switch() */
+
+        fibril_switch(FIBRIL_FROM_BLOCKED);
+        futex_unlock(&async_futex);
 }