Changeset 96c30c8 in mainline

Timestamp:

2018-06-28T15:45:37Z (6 years ago)

Author:

Jiří Zárevúcky <jiri.zarevucky@…>

Branches:

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

Children:

331d024

Parents:

82453b29

git-author:

Jiří Zárevúcky <jiri.zarevucky@…> (2018-06-28 15:36:29)

git-committer:

Jiří Zárevúcky <jiri.zarevucky@…> (2018-06-28 15:45:37)

Message:

Turn ipc_poke() into a regular wakeup on the waitq.

With prior behavior of ignoring the poke when no thread is blocking,
a thread could go to sleep just after a poke meant for it and sleep
indefinitely despite there being work to do.

After the change, worst case scenario, thread enters ipc wait, exits
immediately due to a previous poke, finds no work to do and enters ipc wait
again (possibly repeating the spurious wakeup a few times).

Location:

kernel/generic

Files:

• include/synch/waitq.h (modified) (1 diff)
• src/ipc/ipc.c (modified) (2 diffs)
• src/ipc/sysipc.c (modified) (1 diff)
• src/synch/waitq.c (modified) (1 diff)

kernel/generic/include/synch/waitq.h

@@ -82 +82 @@
 extern void _waitq_wakeup_unsafe(waitq_t *, wakeup_mode_t);
 extern void waitq_interrupt_sleep(struct thread *);
-extern void waitq_unsleep(waitq_t *);
 extern int waitq_count_get(waitq_t *);
 extern void waitq_count_set(waitq_t *, int val);

kernel/generic/src/ipc/ipc.c

@@ -550 +550 @@
         errno_t rc;
 
-restart:
         rc = waitq_sleep_timeout(&box->wq, usec, flags, NULL);
         if (rc != EOK)
@@ -590 +589 @@
                 list_append(&request->ab_link, &box->dispatched_calls);
         } else {
-                /* This can happen regularly after ipc_cleanup */
+                /*
+                 * This can happen regularly after ipc_cleanup, or in
+                 * response to ipc_poke(). Let the caller sort out the wakeup.
+                 */
                 irq_spinlock_unlock(&box->lock, true);
-                goto restart;
+                return NULL;
         }
 

kernel/generic/src/ipc/sysipc.c

@@ -856 +856 @@
 sys_errno_t sys_ipc_poke(void)
 {
-        waitq_unsleep(&TASK->answerbox.wq);
+        waitq_wakeup(&TASK->answerbox.wq, WAKEUP_FIRST);
         return EOK;
 }

kernel/generic/src/synch/waitq.c

@@ -190 +190 @@
         if (do_wakeup)
                 thread_ready(thread);
-}
-
-/** Interrupt the first thread sleeping in the wait queue.
- *
- * Note that the caller somehow needs to know that the thread to be interrupted
- * is sleeping interruptibly.
- *
- * @param wq Pointer to wait queue.
- *
- */
-void waitq_unsleep(waitq_t *wq)
-{
-        irq_spinlock_lock(&wq->lock, true);
-
-        if (!list_empty(&wq->sleepers)) {
-                thread_t *thread = list_get_instance(list_first(&wq->sleepers),
-                    thread_t, wq_link);
-
-                irq_spinlock_lock(&thread->lock, false);
-
-                assert(thread->sleep_interruptible);
-
-                if ((thread->timeout_pending) &&
-                    (timeout_unregister(&thread->sleep_timeout)))
-                        thread->timeout_pending = false;
-
-                list_remove(&thread->wq_link);
-                thread->saved_context = thread->sleep_interruption_context;
-                thread->sleep_queue = NULL;
-
-                irq_spinlock_unlock(&thread->lock, false);
-                thread_ready(thread);
-        }
-
-        irq_spinlock_unlock(&wq->lock, true);
 }