Re: [GIT PULL] scheduler changes for v4.3

[Markus Trippelsdorf <markus@trippelsdorf.de>]

On 2015.08.31 at 19:24 +0200, Ingo Molnar wrote:
> Please pull the latest sched-core-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-core-for-linus
> 
>    # HEAD: ff277d4250fe715b6666219b1a3423b863418794 sched/deadline: Fix comment in enqueue_task_dl()

Linus,

your merge (commit a1d8561172f369ba) breaks booting on my machine.

I wrote down the backtrace:

map_vsyscall
kvm_arch_hardware_setup
map_vsyscall
kvm_init
map_vsyscall
do_one_initcall
kernel_init_freeable
rest_init
kernel_init
ret_from_fork
rest_init

RIP: svm_hardware_setup

Reverting your merge resolution fixes the issue:

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 82cf9dff4295..873aa0757b04 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -397,12 +397,11 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
 	 * Prevent irq alloc/free while the dying cpu reorganizes the
 	 * interrupt affinities.
 	 */
-	irq_lock_sparse();
 
 	/*
 	 * So now all preempt/rcu users must observe !cpu_active().
 	 */
-	err = stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
+	err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 	if (err) {
 		/* CPU didn't die: tell everyone.  Can't complain. */
 		cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);

-- 
Markus