Changeset 8619f25 in mainline

Timestamp:

2009-08-21T07:25:50Z (15 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

207e208e

Parents:

057d21a

Message:

Fibril synchronization needs to have a means to interrupt
idle threads from waiting for IPC and get them to execute
awakened fibrils.

Location:

uspace/lib/libc

Files:

• generic/async.c (modified) (3 diffs)
• generic/fibril_sync.c (modified) (5 diffs)
• include/async.h (modified) (1 diff)

uspace/lib/libc/generic/async.c

@@ -106 +106 @@
 
 atomic_t async_futex = FUTEX_INITIALIZER;
+
+/** Number of threads waiting for IPC in the kernel. */
+atomic_t threads_in_ipc_wait = { 0 };
 
 /** Structures of this type represent a waiting fibril. */
@@ -683 +686 @@
                 
                 futex_up(&async_futex);
+
+                atomic_inc(&threads_in_ipc_wait);
                 
                 ipc_call_t call;
@@ -688 +693 @@
                     SYNCH_FLAGS_NONE);
                 
+                atomic_dec(&threads_in_ipc_wait);
+
                 if (!callid) {
                         handle_expired_timeouts();

uspace/lib/libc/generic/fibril_sync.c

@@ -40 +40 @@
 #include <assert.h>
 
+static void optimize_execution_power(void)
+{
+        /*
+         * When waking up a worker fibril previously blocked in fibril
+         * synchronization, chances are that there is an idle manager fibril
+         * waiting for IPC, that could start executing the awakened worker
+         * fibril right away. We try to detect this and bring the manager
+         * fibril back to fruitful work.
+         */
+        if (atomic_get(&threads_in_ipc_wait) > 0)
+                ipc_poke();
+}
+
 void fibril_mutex_initialize(fibril_mutex_t *fm)
 {
@@ -84 +97 @@
                 list_remove(&f->link);
                 fibril_add_ready((fid_t) f);
+                optimize_execution_power();
         }
 }
@@ -152 +166 @@
                         fibril_add_ready((fid_t) f);
                         frw->writers++;
+                        optimize_execution_power();
                         break;
                 } else {
@@ -157 +172 @@
                         fibril_add_ready((fid_t) f);
                         frw->readers++;
+                        optimize_execution_power();
                 }
         }
@@ -200 +216 @@
                 list_remove(&f->link);
                 fibril_add_ready((fid_t) f);
+                optimize_execution_power();
                 if (once)
                         break;

uspace/lib/libc/include/async.h

@@ -47 +47 @@
 extern atomic_t async_futex;
 
+extern atomic_t threads_in_ipc_wait;
+
 extern int __async_init(void);
 extern ipc_callid_t async_get_call_timeout(ipc_call_t *call, suseconds_t usecs);