Changeset 408 for trunk/kernel/kern/chdev.c

Timestamp:

Dec 5, 2017, 4:20:07 PM (7 years ago)

Author:

alain

Message:

Fix several bugs in the fork() syscall.

File:

• trunk/kernel/kern/chdev.c (modified) (4 diffs)

trunk/kernel/kern/chdev.c

@@ -120 +120 @@
     uint32_t   lid;           // core running the server thread local index
     xptr_t     lock_xp;       // extended pointer on lock protecting the chdev queue
-    uint32_t   modified;      // non zero if the server thread state was modified
+    uint32_t   different;     // non zero if server thread core != client thread core
     uint32_t   save_sr;       // for critical section
 
@@ -152 +152 @@
     lid = hal_remote_lw( XPTR( chdev_cxy , &core_ptr->lid ) );
 
-    // enter critical section
+    // compute server core != thread core
+    different = (lid != this->core->lid) || (local_cxy != chdev_cxy);
+
+    // enter critical section to make atomic : 
+    // (1) client blocking
+    // (2) client registration in server queue 
+    // (3) IPI to force server scheduling
+    // (4) descheduling 
+    // ... in this order
     hal_disable_irq( &save_sr );
+
+    // block current thread
+    thread_block( CURRENT_THREAD , THREAD_BLOCKED_IO );
 
     // register client thread in waiting queue 
@@ -160 +171 @@
     remote_spinlock_unlock( lock_xp );
 
-    // unblock server thread
-    modified = thread_unblock( XPTR( chdev_cxy , server_ptr ), THREAD_BLOCKED_DEV_QUEUE );
-
-    // send IPI to core running the server thread
-    if( modified ) dev_pic_send_ipi( chdev_cxy , lid ); 
+    // send IPI to core running the server thread if required
+    if( different ) dev_pic_send_ipi( chdev_cxy , lid ); 
     
-    // block client thread 
-    assert( thread_can_yield( this ) , __FUNCTION__ , "illegal sched_yield\n" );
-
 chdev_dmsg("\n[DBG] %s : core[%x,%d] (thread %s) deschedules / cycle %d\n",
 __FUNCTION__, local_cxy, this->core->lid, thread_type_str(this->type) , hal_time_stamp() );
 
-    thread_block( CURRENT_THREAD , THREAD_BLOCKED_IO );
-    sched_yield();
+    // deschedule
+    assert( thread_can_yield( this ) , __FUNCTION__ , "illegal sched_yield\n" );
+    sched_yield("blocked on I/O");
 
 chdev_dmsg("\n[DBG] %s : core[%x,%d] (thread %s) resumes / cycle %d\n",
@@ -217 +223 @@
 __FUNCTION__ , server , hal_time_stamp() );
 
-            // block and deschedule
-            thread_block( server , THREAD_BLOCKED_DEV_QUEUE );
-            sched_yield();
+            // deschedule
+            sched_yield("I/O queue empty");
 
 chdev_dmsg("\n[DBG] %s : thread %x resume /cycle %d\n",