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Commit f95ec2bc authored by Heiko Carstens's avatar Heiko Carstens Committed by Greg Kroah-Hartman
Browse files

s390/time: ensure get_clock_monotonic() returns monotonic values 



[ Upstream commit 011620688a71f2f1fe9901dbc2479a7c01053196 ]

The current implementation of get_clock_monotonic() leaves it up to
the caller to call the function with preemption disabled. The only
core kernel caller (sched_clock) however does not disable preemption.

In order to make sure that all callers of this function see monotonic
values handle disabling preemption within the function itself.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 8fa7f8d5

arch/s390/include/asm/timex.h

+10 −6
Original line number Diff line number Diff line
@@ -10,8 +10,9 @@ 
#ifndef _ASM_S390_TIMEX_H

#define _ASM_S390_TIMEX_H



#include <asm/lowcore.h>

#include <linux/preempt.h>

#include <linux/time64.h>

#include <asm/lowcore.h>



/* The value of the TOD clock for 1.1.1970. */

#define TOD_UNIX_EPOCH 0x7d91048bca000000ULL
@@ -186,15 +187,18 @@ extern unsigned char tod_clock_base[16] __aligned(8); 
/**

 * get_clock_monotonic - returns current time in clock rate units

 *

 * The caller must ensure that preemption is disabled.

 * The clock and tod_clock_base get changed via stop_machine.

 * Therefore preemption must be disabled when calling this

 * function, otherwise the returned value is not guaranteed to

 * be monotonic.

 * Therefore preemption must be disabled, otherwise the returned

 * value is not guaranteed to be monotonic.

 */

static inline unsigned long long get_tod_clock_monotonic(void)

{

	return get_tod_clock() - *(unsigned long long *) &tod_clock_base[1];

	unsigned long long tod;



	preempt_disable();

	tod = get_tod_clock() - *(unsigned long long *) &tod_clock_base[1];

	preempt_enable();

	return tod;

}



/**