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Commit fe3cd484 authored by Feng Tang's avatar Feng Tang Committed by Greg Kroah-Hartman
Browse files

x86/tsc: Add a timer to make sure TSC_adjust is always checked 

commit c7719e79347803b8e3b6b50da8c6db410a3012b5 upstream.

The TSC_ADJUST register is checked every time a CPU enters idle state, but
Thomas Gleixner mentioned there is still a caveat that a system won't enter
idle [1], either because it's too busy or configured purposely to not enter
idle.

Setup a periodic timer (every 10 minutes) to make sure the check is
happening on a regular base.

[1] https://lore.kernel.org/lkml/875z286xtk.fsf@nanos.tec.linutronix.de/



Fixes: 6e3cd95234dc ("x86/hpet: Use another crystalball to evaluate HPET usability")
Requested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarFeng Tang <feng.tang@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211117023751.24190-1-feng.tang@intel.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 957a203f

arch/x86/kernel/tsc_sync.c

+41 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ struct tsc_adjust { 
};



static DEFINE_PER_CPU(struct tsc_adjust, tsc_adjust);

static struct timer_list tsc_sync_check_timer;



/*

 * TSC's on different sockets may be reset asynchronously.
@@ -77,6 +78,46 @@ void tsc_verify_tsc_adjust(bool resume) 
	}

}



/*

 * Normally the tsc_sync will be checked every time system enters idle

 * state, but there is still caveat that a system won't enter idle,

 * either because it's too busy or configured purposely to not enter

 * idle.

 *

 * So setup a periodic timer (every 10 minutes) to make sure the check

 * is always on.

 */



#define SYNC_CHECK_INTERVAL		(HZ * 600)



static void tsc_sync_check_timer_fn(struct timer_list *unused)

{

	int next_cpu;



	tsc_verify_tsc_adjust(false);



	/* Run the check for all onlined CPUs in turn */

	next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);

	if (next_cpu >= nr_cpu_ids)

		next_cpu = cpumask_first(cpu_online_mask);



	tsc_sync_check_timer.expires += SYNC_CHECK_INTERVAL;

	add_timer_on(&tsc_sync_check_timer, next_cpu);

}



static int __init start_sync_check_timer(void)

{

	if (!cpu_feature_enabled(X86_FEATURE_TSC_ADJUST) || tsc_clocksource_reliable)

		return 0;



	timer_setup(&tsc_sync_check_timer, tsc_sync_check_timer_fn, 0);

	tsc_sync_check_timer.expires = jiffies + SYNC_CHECK_INTERVAL;

	add_timer(&tsc_sync_check_timer);



	return 0;

}

late_initcall(start_sync_check_timer);



static void tsc_sanitize_first_cpu(struct tsc_adjust *cur, s64 bootval,

				   unsigned int cpu, bool bootcpu)

{