Commit 347abad9 authored by Rik van Riel's avatar Rik van Riel Committed by Ingo Molnar
Browse files

sched, time: Fix build error with 64 bit cputime_t on 32 bit systems 



On 32 bit systems cmpxchg cannot handle 64 bit values, so
some additional magic is required to allow a 32 bit system
with CONFIG_VIRT_CPU_ACCOUNTING_GEN=y enabled to build.

Make sure the correct cmpxchg function is used when doing
an atomic swap of a cputime_t.

Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: umgwanakikbuti@gmail.com
Cc: fweisbec@gmail.com
Cc: srao@redhat.com
Cc: lwoodman@redhat.com
Cc: atheurer@redhat.com
Cc: oleg@redhat.com
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linux390@de.ibm.com
Cc: linux-arch@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Link: http://lkml.kernel.org/r/20140930155947.070cdb1f@annuminas.surriel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 43f4d666

arch/powerpc/include/asm/cputime.h

+2 −0
Original line number Diff line number Diff line
@@ -32,6 +32,8 @@ static inline void setup_cputime_one_jiffy(void) { } 
typedef u64 __nocast cputime_t;

typedef u64 __nocast cputime64_t;



#define cmpxchg_cputime(ptr, old, new) cmpxchg(ptr, old, new)



#ifdef __KERNEL__



/*

arch/s390/include/asm/cputime.h

+2 −0
Original line number Diff line number Diff line
@@ -18,6 +18,8 @@ 
typedef unsigned long long __nocast cputime_t;

typedef unsigned long long __nocast cputime64_t;



#define cmpxchg_cputime(ptr, old, new) cmpxchg64(ptr, old, new)



static inline unsigned long __div(unsigned long long n, unsigned long base)

{

#ifndef CONFIG_64BIT

include/asm-generic/cputime_jiffies.h

+2 −0
Original line number Diff line number Diff line
@@ -3,6 +3,8 @@ 


typedef unsigned long __nocast cputime_t;



#define cmpxchg_cputime(ptr, old, new) cmpxchg(ptr, old, new)



#define cputime_one_jiffy		jiffies_to_cputime(1)

#define cputime_to_jiffies(__ct)	(__force unsigned long)(__ct)

#define cputime_to_scaled(__ct)		(__ct)

include/asm-generic/cputime_nsecs.h

+2 −0
Original line number Diff line number Diff line
@@ -21,6 +21,8 @@ 
typedef u64 __nocast cputime_t;

typedef u64 __nocast cputime64_t;



#define cmpxchg_cputime(ptr, old, new) cmpxchg64(ptr, old, new)



#define cputime_one_jiffy		jiffies_to_cputime(1)



#define cputime_div(__ct, divisor)  div_u64((__force u64)__ct, divisor)

kernel/sched/cputime.c

+19 −10
Original line number Diff line number Diff line
@@ -554,6 +554,23 @@ drop_precision: 
	return (__force cputime_t) scaled;

}



/*

 * Atomically advance counter to the new value. Interrupts, vcpu

 * scheduling, and scaling inaccuracies can cause cputime_advance

 * to be occasionally called with a new value smaller than counter.

 * Let's enforce atomicity.

 *

 * Normally a caller will only go through this loop once, or not

 * at all in case a previous caller updated counter the same jiffy.

 */

static void cputime_advance(cputime_t *counter, cputime_t new)

{

	cputime_t old;



	while (new > (old = ACCESS_ONCE(*counter)))

		cmpxchg_cputime(counter, old, new);

}



/*

 * Adjust tick based cputime random precision against scheduler

 * runtime accounting.
@@ -599,16 +616,8 @@ static void cputime_adjust(struct task_cputime *curr, 
		utime = rtime - stime;

	}



	/*

	 * If the tick based count grows faster than the scheduler one,

	 * the result of the scaling may go backward.

	 * Let's enforce monotonicity.

	 * Atomic exchange protects against concurrent cputime_adjust().

	 */

	while (stime > (rtime = ACCESS_ONCE(prev->stime)))

		cmpxchg(&prev->stime, rtime, stime);

	while (utime > (rtime = ACCESS_ONCE(prev->utime)))

		cmpxchg(&prev->utime, rtime, utime);

	cputime_advance(&prev->stime, stime);

	cputime_advance(&prev->utime, utime);



out:

	*ut = prev->utime;

CRA Git | Maintained and supported by SUSTech CRA and CCSE