Fix domain blocking race

PATCH New Samuel Thibault 1 participant 1 message Nov 23, 2007

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Samuel Thibault

author

2007-11-23 18:15 UTC #0 lore raw

PATCH 1/1 Fix domain blocking race

A callback which wakes a thread may happen between the moment schedule() gives hand to the idle thread and the latter blocks the domain. Idle hence needs to atomically check that no thread is running and block, else awoken threads may have to wait up to 10 seconds.

Signed-off-by Samuel Thibault <[email protected]>

extras/mini-os/sched.c +20 -3

diff -r dc9246357cdb extras/mini-os/sched.c
@@ -216,12 +216,29 @@
 void idle_thread_fn(void *unused)
 {
     s_time_t until;
+    unsigned long flags;
+    struct list_head *iterator;
+    struct thread *next, *thread;
     for(;;)
     {
         schedule();
-        /* block until the next timeout expires, or for 10 secs, whichever comes first */
-        until = blocking_time();
-        block_domain(until);
+        next = NULL;
+        local_irq_save(flags);
+        list_for_each(iterator, &idle_thread->thread_list)
+        {
+            thread = list_entry(iterator, struct thread, thread_list);
+            if(is_runnable(thread)) 
+            {
+                next = thread;
+                break;
+            }
+        }
+        if (!next) {
+            /* block until the next timeout expires, or for 10 secs, whichever comes first */
+            until = blocking_time();
+            block_domain(until);
+        }
+        local_irq_restore(flags);
         wake_expired();
     }
 }