Changeset 625 for trunk/kernel/syscalls/sys_fork.c

Timestamp:

Apr 10, 2019, 10:09:39 AM (5 years ago)

Author:

alain

Message:

Fix a bug in the vmm_remove_vseg() function: the physical pages
associated to an user DATA vseg were released to the kernel when
the target process descriptor was in the reference cluster.
This physical pages release should be done only when the page
forks counter value is zero.
All other modifications are cosmetic.

File:

• trunk/kernel/syscalls/sys_fork.c (modified) (5 diffs)

trunk/kernel/syscalls/sys_fork.c

@@ -2 +2 @@
  * sys_fork.c - Kernel function implementing the "fork" system call.
  * 
- * Authors  Alain Greiner  (2016,2017)
+ * Authors  Alain Greiner  (2016,2017,2018,2019)
  *
  * Copyright (c) UPMC Sorbonne Universites
@@ -73 +73 @@
 #if DEBUG_SYS_FORK
 if( DEBUG_SYS_FORK < tm_start )
-printk("\n[DBG] %s : thread[%x,%x] enter / cycle =  %d\n",
+printk("\n[%s] thread[%x,%x] enter / cycle =  %d\n",
 __FUNCTION__, parent_pid, parent_thread_ptr->trdid, (uint32_t)tm_start );
 #endif
@@ -151 +151 @@
 
     // set remote child CPU context from parent_thread register values
+    // replicates the parent thread kernel stack to the child thread descriptor,
+    // and finally unblock the child thread. 
     hal_cpu_context_fork( XPTR( child_cxy , child_thread_ptr ) );
 
     // From this point, both parent and child threads execute the following code,
-    // but they can be distinguished by the (CURRENT_THREAD,local_cxy) values.
-    // - parent unblock child, and return child PID to user application.
-    // - child thread does nothing, and return 0 to user pplication 
-    // The child thread will only execute it when it is unblocked by parent thread.
+    // but child thread will only execute it after being unblocked by parent thread.
+    // They can be distinguished by the (CURRENT_THREAD,local_cxy) values.
+    // - parent return child PID to user application.
+    // - child  return 0 to user application 
 
     thread_t * current = CURRENT_THREAD;
@@ -165 +167 @@
 #endif
 
+    if( (current == parent_thread_ptr) && (local_cxy == parent_cxy) )   // parent thread
+    {
+
 #if DEBUG_SYS_FORK
 if( DEBUG_SYS_FORK < tm_end )
-printk("\n[%s] thread[%x,%x] exit / cycle %d\n",
-__FUNCTION__, current->process->pid, current->trdid, (uint32_t)tm_end );
+printk("\n[%s] parent thread[%x,%x] exit / child_pid %x / cycle %d\n",
+__FUNCTION__, current->process->pid, current->trdid, child_pid, (uint32_t)tm_end );
 #endif
 
-    if( (current == parent_thread_ptr) && (local_cxy == parent_cxy) )   // parent thread
-    {
-        // parent_thread unblock child_thread
-        thread_unblock( XPTR( child_cxy , child_thread_ptr ) , THREAD_BLOCKED_GLOBAL );
-
-        // only parent contribute to instrumentation
-
+// only parent contribute to instrumentation
 #if CONFIG_INSTRUMENTATION_SYSCALLS
 hal_atomic_add( &syscalls_cumul_cost[SYS_FORK] , tm_end - tm_start );
@@ -186 +185 @@
         else                                                               // child_thread
     {
+
+#if DEBUG_SYS_FORK
+if( DEBUG_SYS_FORK < tm_end )
+printk("\n[%s] child thread[%x,%x] exit / child_pid %x / cycle %d\n",
+__FUNCTION__, current->process->pid, current->trdid, child_pid, (uint32_t)tm_end );
+#endif
+
         return 0;
     }