watchdog: Fix check_preemption_disabled() error

hulk inclusion
category: bugfix
bugzilla: 173968, https://gitee.com/openeuler/kernel/issues/I3J87Y
CVE: NA

-------------------------------------------------

When enabling CONFIG_DEBUG_PREEMPT and CONFIG_PREEMPT, it triggers a 'BUG'
in the pmu based nmi_watchdog initializaion:

[    3.341853] BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
[    3.344392] caller is debug_smp_processor_id+0x17/0x20
[    3.344395] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.10.0+ #398
[    3.344397] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
[    3.344399] Call Trace:
[    3.344410]  dump_stack+0x60/0x76
[    3.344412]  check_preemption_disabled+0xba/0xc0
[    3.344415]  debug_smp_processor_id+0x17/0x20
[    3.344422]  hardlockup_detector_event_create+0xf/0x60
[    3.344427]  hardlockup_detector_perf_init+0xf/0x41
[    3.344430]  watchdog_nmi_probe+0xe/0x10
[    3.344432]  lockup_detector_init+0x22/0x5b
[    3.344437]  kernel_init_freeable+0x20c/0x245
[    3.344439]  ? rest_init+0xd0/0xd0
[    3.344441]  kernel_init+0xe/0x110
[    3.344446]  ret_from_fork+0x22/0x30

This issue was introduced by commit 141482cb, which move down
lockup_detector_init() after do_basic_setup(), after sched_init_smp() too.

  hardlockup_detector_event_create
    |- hardlockup_detector_perf_init	(unsafe)
      |- watchdog_nmi_probe
        |- lockup_detector_init
    |- hardlockup_detector_perf_enable
      |- watchdog_nmi_enable
        |- watchdog_enable
          |- lockup_detector_online_cpu
          |- softlockup_start_fn
            |- softlockup_start_all
              |- lockup_detector_reconfigure
                |- lockup_detector_setup
                  |- lockup_detector_init

After analysing the calling context, it's only unsafe to use
smp_processor_id() in hardlockup_detector_perf_init() as the thread
'kernel_init' is preemptible after sched_init_smp().

While it is just a test if we can enable the pmu based nmi_watchdog, the
real enabling process is in softlockup_start_fn() later which ensures
that watchdog_enable() is called on all cores. So it's free to disable
preempt to fix this 'BUG'.

Fixes: 141482cb ("lockup_detector: init lockup detector after all the init_calls")
Signed-off-by: NWei Li <liwei391@huawei.com>
Reviewed-by: NXiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/watchdog_hld.c

@@ -508,14 +508,17 @@ void __init hardlockup_detector_perf_restart(void)
  */
 int __init hardlockup_detector_perf_init(void)
 {
-	int ret = hardlockup_detector_event_create();
+	int ret;
 
+	preempt_disable();
+	ret = hardlockup_detector_event_create();
 	if (ret) {
 		pr_info("Perf NMI watchdog permanently disabled\n");
 	} else {
 		perf_event_release_kernel(this_cpu_read(watchdog_ev));
 		this_cpu_write(watchdog_ev, NULL);
 	}
+	preempt_enable();
 	return ret;
 }
 #endif /* CONFIG_HARDLOCKUP_DETECTOR_PERF */