Changeset 5663872 in mainline for kernel/generic/src/proc/scheduler.c

Timestamp:

2024-01-14T18:24:05Z (17 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master

Children:

23f36a3

Parents:

4760793

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-02-18 13:37:30)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-01-14 18:24:05)

Message:

Move stuff around for thread sleep

Only mark the thread as ready for wakeup after we switch to
another context. This way, soundness of the sychronization
does not depend on thread lock being held across the context
switch, which gives us more freedom.

File:

• kernel/generic/src/proc/scheduler.c (modified) (2 diffs)

kernel/generic/src/proc/scheduler.c

@@ -443 +443 @@
                 after_thread_ran();
 
+                int expected;
+
                 switch (THREAD->state) {
                 case Running:
@@ -462 +464 @@
 
                 case Sleeping:
-                        /*
-                         * Prefer the thread after it's woken up.
-                         */
-                        THREAD->priority = -1;
-                        irq_spinlock_unlock(&THREAD->lock, false);
+                        expected = SLEEP_INITIAL;
+
+                        /* Only set SLEEP_ASLEEP in sleep pad if it's still in initial state */
+                        if (atomic_compare_exchange_strong_explicit(&THREAD->sleep_state,
+                            &expected, SLEEP_ASLEEP,
+                            memory_order_acq_rel, memory_order_acquire)) {
+
+                                /* Prefer the thread after it's woken up. */
+                                THREAD->priority = -1;
+                                irq_spinlock_unlock(&THREAD->lock, false);
+                        } else {
+                                assert(expected == SLEEP_WOKE);
+                                /* The thread has already been woken up, requeue immediately. */
+                                irq_spinlock_unlock(&THREAD->lock, false);
+                                thread_ready(THREAD);
+                        }
+
                         break;