Re: [PATCH for 2.5] preemptible kernel

Roger Larsson
2001-03-20T18:28:53Z

Hi,

One little readability thing I found.
The prev->state TASK_ value is mostly used as a plain value
but the new TASK_PREEMPTED is or:ed together with whatever was there.
Later when we switch to check the state it is checked against TASK_PREEMPTED
only. Since TASK_RUNNING is 0 it works OK but...

--- sched.c.nigel Tue Mar 20 18:52:43 2001
+++ sched.c.roger Tue Mar 20 19:03:28 2001
@@ -553,7 +553,7 @@
#endif
del_from_runqueue(prev);
#ifdef CONFIG_PREEMPT
- case TASK_PREEMPTED:
+ case TASK_RUNNING | TASK_PREEMPTED:
#endif
case TASK_RUNNING:
}

We could add all/(other common) combinations as cases

switch (prev->state) {
case TASK_INTERRUPTIBLE:
if (signal_pending(prev)) {
prev->state = TASK_RUNNING;
break;
}
default:
#ifdef CONFIG_PREEMPT
if (prev->state & TASK_PREEMPTED)
break;
#endif
del_from_runqueue(prev);
#ifdef CONFIG_PREEMPT
case TASK_RUNNING | TASK_PREEMPTED:
case TASK_INTERRUPTIBLE | TASK_PREEMPTED:
case TASK_UNINTERRUPTIBLE | TASK_PREEMPTED:
#endif
case TASK_RUNNING:
}

Then the break in default case could almost be replaced with a BUG()...
(I have not checked the generated code)

/RogerL