diff options
| -rw-r--r-- | arch/powerpc/include/asm/cputime.h | 2 | ||||
| -rw-r--r-- | arch/s390/include/asm/cputime.h | 2 | ||||
| -rw-r--r-- | include/asm-generic/cputime_jiffies.h | 2 | ||||
| -rw-r--r-- | include/asm-generic/cputime_nsecs.h | 2 | ||||
| -rw-r--r-- | kernel/sched/cputime.c | 29 |
5 files changed, 27 insertions, 10 deletions
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h index 607559ab271f..6c840ceab820 100644 --- a/arch/powerpc/include/asm/cputime.h +++ b/arch/powerpc/include/asm/cputime.h @@ -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__ /* diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h index f65bd3634519..3001887f94b7 100644 --- a/arch/s390/include/asm/cputime.h +++ b/arch/s390/include/asm/cputime.h @@ -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 diff --git a/include/asm-generic/cputime_jiffies.h b/include/asm-generic/cputime_jiffies.h index d5cb78f53986..fe386fc6e85e 100644 --- a/include/asm-generic/cputime_jiffies.h +++ b/include/asm-generic/cputime_jiffies.h @@ -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) diff --git a/include/asm-generic/cputime_nsecs.h b/include/asm-generic/cputime_nsecs.h index 4e817606c549..0419485891f2 100644 --- a/include/asm-generic/cputime_nsecs.h +++ b/include/asm-generic/cputime_nsecs.h @@ -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) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 64492dff8a81..8394b1ee600c 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -555,6 +555,23 @@ drop_precision: } /* + * 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; |