[PATCH] tick/broadcast: Fix smp_processor_id()-in-preemptible warnings

[Yu Liao]

David reports that commit f7d43dd206e7 ("tick/broadcast: Make takeover
of broadcast hrtimer reliable") introduced the following splat with
CONFIG_DEBUG_PREEMPT enabled:

 [ 1734.414952] BUG: using smp_processor_id() in preemptible [00000000] code: systemd-sleep/4619
 [ 1734.414957] caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0
 [ 1734.414964] CPU: 0 UID: 0 PID: 4619 Comm: systemd-sleep Tainted: P           OE      6.11.0-rc1-linan-4 #292
 [ 1734.414968] Tainted: [P]=PROPRIETARY_MODULE, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
 [ 1734.414969] Hardware name: Micro-Star International Co., Ltd. MS-7B89/B450M MORTAR MAX (MS-7B89), BIOS 2.80 06/10/2020
 [ 1734.414970] Call Trace:
 [ 1734.414974]  <TASK>
 [ 1734.414978]  dump_stack_lvl+0x60/0x80
 [ 1734.414982]  check_preemption_disabled+0xce/0xe0
 [ 1734.414987]  hotplug_cpu__broadcast_tick_pull+0x1c/0xc0
 [ 1734.414996]  takedown_cpu+0x97/0x130
 [ 1734.414999]  cpuhp_invoke_callback+0xf8/0x450

this_cpu_ptr() calls smp_processor_id() in a preemptible context. Fix
this by moving the this_cpu operation to interrupt disable code segment.

Also, use __this_cpu_read() instead of this_cpu_ptr() to save a few
instructions.

this_cpu_ptr(&tick_cpu_device):
  callq  0xffffffff81ef4a30 <debug_smp_processor_id>
  mov    $0x20b60,%r12
  mov    %eax,%eax
  add    -0x7d7cb4e0(,%rax,8),%r12
  callq  0xffffffff81ef4a30 <debug_smp_processor_id>
  mov    %eax,%eax
  lock btr %rax,0x23f5fc6(%rip)
  mov    (%r12),%rax
  mov    $0x1,%esi
  mov    0x18(%rax),%rdi

__this_cpu_read(tick_cpu_device.evtdev):
  mov    $0xffffffff82742a33,%rdi
  callq  0xffffffff81ef4a60 <__this_cpu_preempt_check>
  mov    %gs:0x7eed2098(%rip),%r12        # 0x20b60 <tick_cpu_device>
  callq  0xffffffff81ef4a30 <debug_smp_processor_id>
  mov    %eax,%eax
  lock btr %rax,0x23f5fc8(%rip)
  mov    0x18(%r12),%rdi
  mov    $0x1,%esi

Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable")
Reported-by: David Wang <00107082@xxxxxxx>
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Yu Liao <liaoyu15@xxxxxxxxxx>
---
 kernel/time/tick-broadcast.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index b4843099a8da..85f7d0017e90 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -1141,7 +1141,6 @@ void tick_broadcast_switch_to_oneshot(void)
 #ifdef CONFIG_HOTPLUG_CPU
 void hotplug_cpu__broadcast_tick_pull(int deadcpu)
 {
-	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 	struct clock_event_device *bc;
 	unsigned long flags;
 
@@ -1167,8 +1166,10 @@ void hotplug_cpu__broadcast_tick_pull(int deadcpu)
 		 * device to avoid the starvation.
 		 */
 		if (tick_check_broadcast_expired()) {
+			struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+
 			cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask);
-			tick_program_event(td->evtdev->next_event, 1);
+			tick_program_event(dev->next_event, 1);
 		}
 
 		/* This moves the broadcast assignment to this CPU: */
-- 
2.33.0