s390/idle: convert open coded idle time seqcount

s390 uses open coded seqcount to synchronize idle time accounting.
Lets consolidate it with the standard API.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/include/asm/idle.h b/arch/s390/include/asm/idle.h
index 6af037f574b87517073b9bd92219d860eedf3d1a..113cd963dbbef445b99fc6d51fe74171bdcc4e4e 100644 (file)
--- a/arch/s390/include/asm/idle.h
+++ b/arch/s390/include/asm/idle.h
@@ -9,9 +9,10 @@
 
 #include <linux/types.h>
 #include <linux/device.h>
+#include <linux/seqlock.h>
 
 struct s390_idle_data {
-       unsigned int sequence;
+       seqcount_t seqcount;
        unsigned long long idle_count;
        unsigned long long idle_time;
        unsigned long long clock_idle_enter;

diff --git a/arch/s390/kernel/idle.c b/arch/s390/kernel/idle.c
index 8814dd9cf6444577ddcf2558dbe8c423c2233af9..7a55c29b0b33a8ab4bbdc0c1ca7d7ba2dacdc3ab 100644 (file)
--- a/arch/s390/kernel/idle.c
+++ b/arch/s390/kernel/idle.c
@@ -38,15 +38,13 @@ void enabled_wait(void)
        trace_hardirqs_off();
 
        /* Account time spent with enabled wait psw loaded as idle time. */
-       idle->sequence++;
-       smp_wmb();
+       write_seqcount_begin(&idle->seqcount);
        idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
        idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
        idle->idle_time += idle_time;
        idle->idle_count++;
        account_idle_time(idle_time);
-       smp_wmb();
-       idle->sequence++;
+       write_seqcount_end(&idle->seqcount);
 }
 NOKPROBE_SYMBOL(enabled_wait);
 
@@ -55,14 +53,14 @@ static ssize_t show_idle_count(struct device *dev,
 {
        struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
        unsigned long long idle_count;
-       unsigned int sequence;
+       unsigned int seq;
 
        do {
-               sequence = ACCESS_ONCE(idle->sequence);
+               seq = read_seqcount_begin(&idle->seqcount);
                idle_count = ACCESS_ONCE(idle->idle_count);
                if (ACCESS_ONCE(idle->clock_idle_enter))
                        idle_count++;
-       } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
+       } while (read_seqcount_retry(&idle->seqcount, seq));
        return sprintf(buf, "%llu\n", idle_count);
 }
 DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);
@@ -72,15 +70,15 @@ static ssize_t show_idle_time(struct device *dev,
 {
        struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
        unsigned long long now, idle_time, idle_enter, idle_exit;
-       unsigned int sequence;
+       unsigned int seq;
 
        do {
                now = get_tod_clock();
-               sequence = ACCESS_ONCE(idle->sequence);
+               seq = read_seqcount_begin(&idle->seqcount);
                idle_time = ACCESS_ONCE(idle->idle_time);
                idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
                idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
-       } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
+       } while (read_seqcount_retry(&idle->seqcount, seq));
        idle_time += idle_enter ? ((idle_exit ? : now) - idle_enter) : 0;
        return sprintf(buf, "%llu\n", idle_time >> 12);
 }
@@ -90,14 +88,14 @@ cputime64_t arch_cpu_idle_time(int cpu)
 {
        struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
        unsigned long long now, idle_enter, idle_exit;
-       unsigned int sequence;
+       unsigned int seq;
 
        do {
                now = get_tod_clock();
-               sequence = ACCESS_ONCE(idle->sequence);
+               seq = read_seqcount_begin(&idle->seqcount);
                idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
                idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
-       } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
+       } while (read_seqcount_retry(&idle->seqcount, seq));
        return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
 }