Interrupt starvation points

[Daniel Walker <dwalker@mvista.com>]

        I found some points during schedule when interrupts are off for
long periods . These two patches seem to help. One enables interrupts
inside schedule() , so that interrupts are enabled after each
need-resched loop, then disabled again before __schedule() is called. 

        The other patch enabled interrupt before calling up on
kernel_sem ..This one could use some thinking over. I did this cause
up() is very expensive on ARM , and combined with the looping above
interrupts can stay off for a long time .. 


Daniel


Index: linux-2.6.10/kernel/sched.c
===================================================================
--- linux-2.6.10.orig/kernel/sched.c	2005-02-08 22:32:48.000000000 +0000
+++ linux-2.6.10/kernel/sched.c	2005-02-08 22:33:58.000000000 +0000
@@ -3038,9 +3038,10 @@
 		send_sig(SIGUSR2, current, 1);
 	}
 	do {
+		local_irq_disable();
 		__schedule();
+		local_irq_enable(); // TODO: do sti; ret
 	} while (unlikely(test_thread_flag(TIF_NEED_RESCHED)));
-	local_irq_enable(); // TODO: do sti; ret
 }
 
 EXPORT_SYMBOL(schedule);


Index: linux-2.6.10/lib/kernel_lock.c
===================================================================
--- linux-2.6.10.orig/lib/kernel_lock.c	2005-02-08 18:16:30.000000000 +0000
+++ linux-2.6.10/lib/kernel_lock.c	2005-02-08 22:53:09.000000000 +0000
@@ -114,7 +114,9 @@
 
 void __lockfunc __release_kernel_lock(void)
 {
+	local_irq_enable();
 	up(&kernel_sem);
+	local_irq_disable();
 }
 
 /*