[PATCH] schedule() in_atomic() fix

From: Robert Love (rml@tech9.net)
Date: Tue Sep 17 2002 - 23:46:43 EST


Linus,

Attached patch fixes the scheduler in_atomic() problem with kernel
preemption enabled (and is also working - when kernel preemption is on,
it finds a couple issues during boot).

I hope this approach is to your liking.

Patch is against current BK, please apply.

        Robert Love

diff -urN linux-2.5.36/kernel/sched.c linux/kernel/sched.c
--- linux-2.5.36/kernel/sched.c Tue Sep 17 20:58:48 2002
+++ linux/kernel/sched.c Wed Sep 18 00:41:09 2002
@@ -940,9 +940,6 @@
         struct list_head *queue;
         int idx;
 
- if (unlikely(in_atomic()))
- BUG();
-
 #if CONFIG_DEBUG_HIGHMEM
         check_highmem_ptes();
 #endif
@@ -950,8 +947,20 @@
         preempt_disable();
         prev = current;
         rq = this_rq();
-
         release_kernel_lock(prev);
+
+ /*
+ * Test if we are atomic. Since do_exit() needs to call into
+ * schedule() atomically, we ignore that for now. Otherwise,
+ * whine if we are scheduling when we should not be.
+ */
+ if (likely(current->state != TASK_ZOMBIE)) {
+ if (unlikely((preempt_count() & ~PREEMPT_ACTIVE) != 1)) {
+ printk(KERN_ERR "scheduling while non-atomic!\n");
+ dump_stack();
+ }
+ }
+
         prev->sleep_timestamp = jiffies;
         spin_lock_irq(&rq->lock);
 

-
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