[PATCH] sched/clock: disable irq for generic_sched_clock_init

[Pavel Tatashin]

sched_clock_init() used be called early in boot  when IRQs are still
disabled. Now, it is called when IRQs are already enabled, and this
triggers some warning:

WARNING: CPU: 0 PID: 0 at kernel/time/sched_clock.c:180
sched_clock_register+0x44/0x278
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 4.18.0-rc6-next-20180724 #1
Hardware name: ARM Integrator/CP (Device Tree)
[<c0010cb4>] (unwind_backtrace) from [<c000dc24>] (show_stack+0x10/0x18)
[<c000dc24>] (show_stack) from [<c03ffb94>] (dump_stack+0x18/0x24)
[<c03ffb94>] (dump_stack) from [<c001a000>] (__warn+0xc8/0xf0)
[<c001a000>] (__warn) from [<c001a13c>] (warn_slowpath_null+0x3c/0x4c)
[<c001a13c>] (warn_slowpath_null) from [<c052367c>] (sched_clock_register+0x44/0x278)
[<c052367c>] (sched_clock_register) from [<c05238d8>] (generic_sched_clock_init+0x28/0x88)
[<c05238d8>] (generic_sched_clock_init) from [<c0521a00>] (sched_clock_init+0x54/0x74)
[<c0521a00>] (sched_clock_init) from [<c0519c18>] (start_kernel+0x310/0x3e4)
[<c0519c18>] (start_kernel) from [<00000000>] (  (null))
---[ end trace 08080eb81afa002c ]---

Disable IRQs for the duration of generic_sched_clock_init().

Fixes: 857baa87b642 ("sched/clock: Enable sched clock early")

Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
 kernel/sched/clock.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index 811a39aca1ce..e3e3b979f9bd 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -452,7 +452,9 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
 void __init sched_clock_init(void)
 {
 	static_branch_inc(&sched_clock_running);
+	local_irq_disable();
 	generic_sched_clock_init();
+	local_irq_enable();
 }
 
 u64 sched_clock_cpu(int cpu)
-- 
2.18.0