Use boot based time for process start time and boot time in /proc

Commit 411187fb05cd11676b0979d9fbf3291db69dbce2 caused boot time to move and
process start times to become invalid after suspend.  Using boot based time
for those restores the old behaviour and fixes the issue.

[akpm@linux-foundation.org: little cleanup]
Signed-off-by: Tomas Janousek <tjanouse@redhat.com>
Cc: Tomas Smetana <tsmetana@redhat.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/array.c

@@ -440,8 +440,9 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
 
 	/* Temporary variable needed for gcc-2.96 */
 	/* convert timespec -> nsec*/
-	start_time = (unsigned long long)task->start_time.tv_sec * NSEC_PER_SEC
-				+ task->start_time.tv_nsec;
+	start_time =
+		(unsigned long long)task->real_start_time.tv_sec * NSEC_PER_SEC
+				+ task->real_start_time.tv_nsec;
 	/* convert nsec -> ticks */
 	start_time = nsec_to_clock_t(start_time);
 

fs/proc/proc_misc.c

@@ -443,12 +443,12 @@ static int show_stat(struct seq_file *p, void *v)
 	unsigned long jif;
 	cputime64_t user, nice, system, idle, iowait, irq, softirq, steal;
 	u64 sum = 0;
+	struct timespec boottime;
 
 	user = nice = system = idle = iowait =
 		irq = softirq = steal = cputime64_zero;
-	jif = - wall_to_monotonic.tv_sec;
-	if (wall_to_monotonic.tv_nsec)
-		--jif;
+	getboottime(&boottime);
+	jif = boottime.tv_sec;
 
 	for_each_possible_cpu(i) {
 		int j;

include/linux/sched.h

@@ -972,7 +972,8 @@ struct task_struct {
 	unsigned int rt_priority;
 	cputime_t utime, stime;
 	unsigned long nvcsw, nivcsw; /* context switch counts */
-	struct timespec start_time;
+	struct timespec start_time; 		/* monotonic time */
+	struct timespec real_start_time;	/* boot based time */
 /* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
 	unsigned long min_flt, maj_flt;
 

kernel/fork.c

@@ -1059,6 +1059,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 
 	p->lock_depth = -1;		/* -1 = no lock */
 	do_posix_clock_monotonic_gettime(&p->start_time);
+	p->real_start_time = p->start_time;
+	monotonic_to_bootbased(&p->real_start_time);
 	p->security = NULL;
 	p->io_context = NULL;
 	p->io_wait = NULL;