From 4c1051e37a0e2a941115c6fb7ba08c318f25a0f9 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Sun, 11 Mar 2012 11:59:27 -0400 Subject: [S390] rework idle code Whenever the cpu loads an enabled wait PSW it will appear as idle to the underlying host system. The code in default_idle calls vtime_stop_cpu which does the necessary voodoo to get the cpu time accounting right. The udelay code just loads an enabled wait PSW. To correct this rework the vtime_stop_cpu/vtime_start_cpu logic and move the difficult parts to entry[64].S, vtime_stop_cpu can now be called from anywhere and vtime_start_cpu is gone. The correction of the cpu time during wakeup from an enabled wait PSW is done with a critical section in entry[64].S. As vtime_start_cpu is gone, s390_idle_check can be removed as well. Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/vtime.c | 163 +++++++++-------------------------------------- 1 file changed, 31 insertions(+), 132 deletions(-) (limited to 'arch/s390/kernel/vtime.c') diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index 7bacee9a546f..277ea712b232 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -26,6 +26,7 @@ #include #include #include +#include "entry.h" static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer); @@ -123,153 +124,53 @@ void account_system_vtime(struct task_struct *tsk) } EXPORT_SYMBOL_GPL(account_system_vtime); -void __kprobes vtime_start_cpu(__u64 int_clock, __u64 enter_timer) +void __kprobes vtime_stop_cpu(void) { struct s390_idle_data *idle = &__get_cpu_var(s390_idle); struct vtimer_queue *vq = &__get_cpu_var(virt_cpu_timer); - __u64 idle_time, expires; + unsigned long long idle_time; + unsigned long psw_mask; - if (idle->idle_enter == 0ULL) - return; + trace_hardirqs_on(); + /* Don't trace preempt off for idle. */ + stop_critical_timings(); - /* Account time spent with enabled wait psw loaded as idle time. */ - idle_time = int_clock - idle->idle_enter; - account_idle_time(idle_time); - S390_lowcore.steal_timer += - idle->idle_enter - S390_lowcore.last_update_clock; - S390_lowcore.last_update_clock = int_clock; - - /* Account system time spent going idle. */ - S390_lowcore.system_timer += S390_lowcore.last_update_timer - vq->idle; - S390_lowcore.last_update_timer = enter_timer; - - /* Restart vtime CPU timer */ - if (vq->do_spt) { - /* Program old expire value but first save progress. */ - expires = vq->idle - enter_timer; - expires += get_vtimer(); - set_vtimer(expires); - } else { - /* Don't account the CPU timer delta while the cpu was idle. */ - vq->elapsed -= vq->idle - enter_timer; - } + /* Wait for external, I/O or machine check interrupt. */ + psw_mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_DAT | + PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK; + idle->nohz_delay = 0; + /* Call the assembler magic in entry.S */ + psw_idle(idle, vq, psw_mask, !list_empty(&vq->list)); + + /* Reenable preemption tracer. */ + start_critical_timings(); + + /* Account time spent with enabled wait psw loaded as idle time. */ idle->sequence++; smp_wmb(); + idle_time = idle->idle_exit - idle->idle_enter; idle->idle_time += idle_time; - idle->idle_enter = 0ULL; + idle->idle_enter = idle->idle_exit = 0ULL; idle->idle_count++; + account_idle_time(idle_time); smp_wmb(); idle->sequence++; } -void __kprobes vtime_stop_cpu(void) -{ - struct s390_idle_data *idle = &__get_cpu_var(s390_idle); - struct vtimer_queue *vq = &__get_cpu_var(virt_cpu_timer); - psw_t psw; - - /* Wait for external, I/O or machine check interrupt. */ - psw.mask = psw_kernel_bits | PSW_MASK_WAIT | - PSW_MASK_DAT | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK; - - idle->nohz_delay = 0; - - /* Check if the CPU timer needs to be reprogrammed. */ - if (vq->do_spt) { - __u64 vmax = VTIMER_MAX_SLICE; - /* - * The inline assembly is equivalent to - * vq->idle = get_cpu_timer(); - * set_cpu_timer(VTIMER_MAX_SLICE); - * idle->idle_enter = get_clock(); - * __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT | - * PSW_MASK_DAT | PSW_MASK_IO | - * PSW_MASK_EXT | PSW_MASK_MCHECK); - * The difference is that the inline assembly makes sure that - * the last three instruction are stpt, stck and lpsw in that - * order. This is done to increase the precision. - */ - asm volatile( -#ifndef CONFIG_64BIT - " basr 1,0\n" - "0: ahi 1,1f-0b\n" - " st 1,4(%2)\n" -#else /* CONFIG_64BIT */ - " larl 1,1f\n" - " stg 1,8(%2)\n" -#endif /* CONFIG_64BIT */ - " stpt 0(%4)\n" - " spt 0(%5)\n" - " stck 0(%3)\n" -#ifndef CONFIG_64BIT - " lpsw 0(%2)\n" -#else /* CONFIG_64BIT */ - " lpswe 0(%2)\n" -#endif /* CONFIG_64BIT */ - "1:" - : "=m" (idle->idle_enter), "=m" (vq->idle) - : "a" (&psw), "a" (&idle->idle_enter), - "a" (&vq->idle), "a" (&vmax), "m" (vmax), "m" (psw) - : "memory", "cc", "1"); - } else { - /* - * The inline assembly is equivalent to - * vq->idle = get_cpu_timer(); - * idle->idle_enter = get_clock(); - * __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT | - * PSW_MASK_DAT | PSW_MASK_IO | - * PSW_MASK_EXT | PSW_MASK_MCHECK); - * The difference is that the inline assembly makes sure that - * the last three instruction are stpt, stck and lpsw in that - * order. This is done to increase the precision. - */ - asm volatile( -#ifndef CONFIG_64BIT - " basr 1,0\n" - "0: ahi 1,1f-0b\n" - " st 1,4(%2)\n" -#else /* CONFIG_64BIT */ - " larl 1,1f\n" - " stg 1,8(%2)\n" -#endif /* CONFIG_64BIT */ - " stpt 0(%4)\n" - " stck 0(%3)\n" -#ifndef CONFIG_64BIT - " lpsw 0(%2)\n" -#else /* CONFIG_64BIT */ - " lpswe 0(%2)\n" -#endif /* CONFIG_64BIT */ - "1:" - : "=m" (idle->idle_enter), "=m" (vq->idle) - : "a" (&psw), "a" (&idle->idle_enter), - "a" (&vq->idle), "m" (psw) - : "memory", "cc", "1"); - } -} - cputime64_t s390_get_idle_time(int cpu) { - struct s390_idle_data *idle; - unsigned long long now, idle_time, idle_enter; + struct s390_idle_data *idle = &per_cpu(s390_idle, cpu); + unsigned long long now, idle_enter, idle_exit; unsigned int sequence; - idle = &per_cpu(s390_idle, cpu); - - now = get_clock(); -repeat: - sequence = idle->sequence; - smp_rmb(); - if (sequence & 1) - goto repeat; - idle_time = 0; - idle_enter = idle->idle_enter; - if (idle_enter != 0ULL && idle_enter < now) - idle_time = now - idle_enter; - smp_rmb(); - if (idle->sequence != sequence) - goto repeat; - return idle_time; + do { + now = get_clock(); + sequence = ACCESS_ONCE(idle->sequence); + idle_enter = ACCESS_ONCE(idle->idle_enter); + idle_exit = ACCESS_ONCE(idle->idle_exit); + } while ((sequence & 1) || (idle->sequence != sequence)); + return idle_enter ? ((idle_exit ? : now) - idle_enter) : 0; } /* @@ -346,7 +247,6 @@ static void do_cpu_timer_interrupt(unsigned int ext_int_code, } spin_unlock(&vq->lock); - vq->do_spt = list_empty(&cb_list); do_callbacks(&cb_list); /* next event is first in list */ @@ -355,8 +255,7 @@ static void do_cpu_timer_interrupt(unsigned int ext_int_code, if (!list_empty(&vq->list)) { event = list_first_entry(&vq->list, struct vtimer_list, entry); next = event->expires; - } else - vq->do_spt = 0; + } spin_unlock(&vq->lock); /* * To improve precision add the time spent by the -- cgit v1.2.3-55-g7522