For non 64-bit platforms, convert cpustat fields to atomic64 type so reads and udpates of cpustats are atomic on those platforms as well.
For 64-bit platforms, the cpustat field is left as u64 because on 64-bit, using atomic64_add will have the additional overhead of a lock. We could also have used atomic64_set(atomic64_read() + delta), but on 32-bit platforms using the generic 64-bit ops (lib/atomic64.c), that results in taking a lock twice.
Signed-off-by: Kevin Hilman khilman@linaro.org --- include/linux/kernel_stat.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index df8ad75..a433f87 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -32,7 +32,11 @@ enum cpu_usage_stat { };
struct kernel_cpustat { +#ifdef CONFIG_64BIT u64 _cpustat[NR_STATS]; +#else + atomic64_t _cpustat[NR_STATS]; +#endif };
struct kernel_stat { @@ -51,11 +55,23 @@ DECLARE_PER_CPU(struct kernel_cpustat, kernel_cpustat); #define kcpustat_this_cpu (&__get_cpu_var(kernel_cpustat)) #define kstat_cpu(cpu) per_cpu(kstat, cpu) #define kcpustat_cpu(cpu) per_cpu(kernel_cpustat, cpu) +#ifdef CONFIG_64BIT #define kcpustat_cpu_get(cpu, i) (kcpustat_cpu(cpu)._cpustat[i]) #define kcpustat_cpu_set(cpu, i, val) (kcpustat_cpu(cpu)._cpustat[i] = (val)) #define kcpustat_cpu_add(cpu, i, val) (kcpustat_cpu(cpu)._cpustat[i] += (val)) #define kcpustat_this_cpu_set(i, val) (kcpustat_this_cpu->_cpustat[i] = (val)) #define kcpustat_this_cpu_add(i, val) (kcpustat_this_cpu->_cpustat[i] += (val)) +#else +#define kcpustat_cpu_get(cpu, i) atomic64_read(&kcpustat_cpu(cpu)._cpustat[i]) +#define kcpustat_cpu_set(cpu, i, val) \ + atomic64_set(val, &kcpustat_cpu(cpu)._cpustat[i]) +#define kcpustat_cpu_add(cpu, i, val) \ + atomic64_add(val, &kcpustat_cpu(cpu)._cpustat[i]) +#define kcpustat_this_cpu_set(i, val) \ + atomic64_set(val, &kcpustat_this_cpu->_cpustat[i]) +#define kcpustat_this_cpu_add(i, val) \ + atomic64_add(val, &kcpustat_this_cpu->_cpustat[i]) +#endif
extern unsigned long long nr_context_switches(void);