Re: [PATCH] kernel: use ktime_get_real_ts64() to calculate acct.ac_btime

Peter Zijlstra
2019-11-07T12:46:27Z

On Thu, Nov 07, 2019 at 01:40:47PM +0100, Thomas Gleixner wrote:
> Typing real_start_time makes me really cringe.

I have a patch fixing that...

---
Subject: kernel: Rename tsk->real_start_time
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu Nov 7 11:07:58 CET 2019

Since it stores CLOCK_BOOTTIME, not, as the name suggests,
CLOCK_REALTIME, let's rename real_start_time.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1132,7 +1132,7 @@ static int de_thread(struct task_struct
* also take its birthdate (always earlier than our own).
*/
tsk->start_time = leader->start_time;
- tsk->real_start_time = leader->real_start_time;
+ tsk->start_boottime = leader->start_boottime;

BUG_ON(!same_thread_group(leader, tsk));
BUG_ON(has_group_leader_pid(tsk));
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -533,7 +533,7 @@ static int do_task_stat(struct seq_file
nice = task_nice(task);

/* convert nsec -> ticks */
- start_time = nsec_to_clock_t(task->real_start_time);
+ start_time = nsec_to_clock_t(task->start_boottime);

seq_put_decimal_ull(m, "", pid_nr_ns(pid, ns));
seq_puts(m, " (");
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -879,7 +879,7 @@ struct task_struct {
u64 start_time;

/* Boot based time in nsecs: */
- u64 real_start_time;
+ u64 start_boottime;

/* MM fault and swap info: this can arguably be seen as either mm-specific or thread-specific: */
unsigned long min_flt;
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2130,7 +2130,7 @@ static __latent_entropy struct task_stru
*/

p->start_time = ktime_get_ns();
- p->real_start_time = ktime_get_boottime_ns();
+ p->start_boottime = ktime_get_boottime_ns();

/*
* Make it visible to the rest of the system, but dont wake it up yet.