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after enqueue()ing a process, only pick_proc() a new one if the current

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process is not PREEMPTIBLE (or it's not ready, or there isn't a current
process yet). This fixes a case where a process that isn't
PREEMPTIBLE actually gets preempted. (This solves a race condition
between CLOCK and SYSTEM.)
This commit is contained in:
Ben Gras 2007-03-21 09:45:01 +00:00
parent 4e63801916
commit bd2ddd5fd4
1 changed files with 10 additions and 4 deletions
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14
kernel/proc.c
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@ -523,8 +523,14 @@ register struct proc *rp; /* this process is now runnable */
rp->p_nextready = NIL_PROC; /* mark new end */ rp->p_nextready = NIL_PROC; /* mark new end */
} }
/* Now select the next process to run. */ /* Now select the next process to run, if there isn't a current
pick_proc(); * process yet or current process isn't ready any more, or
* it's PREEMPTIBLE.
*/
if(!proc_ptr || proc_ptr->p_rts_flags ||
(priv(proc_ptr)->s_flags & PREEMPTIBLE)) {
pick_proc();
}
#if DEBUG_SCHED_CHECK #if DEBUG_SCHED_CHECK
rp->p_ready = 1; rp->p_ready = 1;
@ -554,8 +560,7 @@ register struct proc *rp; /* this process is no longer runnable */
#if DEBUG_SCHED_CHECK #if DEBUG_SCHED_CHECK
check_runqueues("dequeue1"); check_runqueues("dequeue1");
if (! rp->p_ready) kprintf("%s:%d: dequeue() already unready process\n", if (! rp->p_ready) kprintf("dequeue() already unready process\n");
f_str, f_line);
#endif #endif
/* Now make sure that the process is not in its ready queue. Remove the /* Now make sure that the process is not in its ready queue. Remove the
@ -639,6 +644,7 @@ PRIVATE void pick_proc()
return; return;
} }
} }
panic("no ready process", NO_NUM);
} }
/*===========================================================================* /*===========================================================================*