2.6.11-rc1: local_irq_disable() in main.c:rest_init() hangs ADB driver

[Mikael Pettersson]

2.6.11-rc1 causes the powermac ADB driver, which controls
the keyboard and mouse on pre-USB powermacs, to hang during
bootup. The last kernel message seen is:

adb: starting probe task...

and then the machine hangs hard. 2.6.10 did not have this problem.

The problem appears to be caused by the local_irq_disable()
added to init/main.c:rest_init() in 2.6.10-bk12:

--- a/init/main.c	2005-01-11 20:02:35 -08:00
+++ b/init/main.c	2005-01-11 20:02:35 -08:00
@@ -445,6 +373,12 @@
 {
 	kernel_thread(init, NULL, CLONE_FS | CLONE_SIGHAND);
 	numa_default_policy();
+	/*
+	 * Re-enable preemption but disable interrupts to make sure
+	 * we dont get preempted until we schedule() in cpu_idle().
+	 */
+	local_irq_disable();
+	preempt_enable_no_resched();
 	unlock_kernel();
  	cpu_idle();
 } 

Commenting out that local_irq_disable() makes the machine
boot Ok again.

The machine is a Beige G3, SMP=n, PREEMPT=n, ADB=y, ADB_CUDA=y.

/Mikael
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