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Subject[PATCH 4.12 176/196] sched/cputime: Rename vtime fields
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Frederic Weisbecker <fweisbec@gmail.com>

commit 60a9ce57e7c5ac1df3a39fb941022bbfa40c0862 upstream.

The current "snapshot" based naming on vtime fields suggests we record
some past event but that's a low level picture of their actual purpose
which comes out blurry. The real point of these fields is to run a basic
state machine that tracks down cputime entry while switching between
contexts.

So lets reflect that with more meaningful names.

Tested-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1498756511-11714-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/init_task.h | 4 ++--
include/linux/sched.h | 4 ++--
kernel/fork.c | 4 ++--
kernel/sched/cputime.c | 30 +++++++++++++++---------------
4 files changed, 21 insertions(+), 21 deletions(-)

--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -171,8 +171,8 @@ extern struct cred init_cred;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
# define INIT_VTIME(tsk) \
.vtime_seqcount = SEQCNT_ZERO(tsk.vtime_seqcount), \
- .vtime_snap = 0, \
- .vtime_snap_whence = VTIME_SYS,
+ .vtime_starttime = 0, \
+ .vtime_state = VTIME_SYS,
#else
# define INIT_VTIME(tsk)
#endif
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -671,7 +671,7 @@ struct task_struct {
struct prev_cputime prev_cputime;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqcount_t vtime_seqcount;
- unsigned long long vtime_snap;
+ unsigned long long vtime_starttime;
enum {
/* Task is sleeping or running in a CPU with VTIME inactive: */
VTIME_INACTIVE = 0,
@@ -679,7 +679,7 @@ struct task_struct {
VTIME_USER,
/* Task runs in kernelspace in a CPU with VTIME active: */
VTIME_SYS,
- } vtime_snap_whence;
+ } vtime_state;
#endif

#ifdef CONFIG_NO_HZ_FULL
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1638,8 +1638,8 @@ static __latent_entropy struct task_stru

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqcount_init(&p->vtime_seqcount);
- p->vtime_snap = 0;
- p->vtime_snap_whence = VTIME_INACTIVE;
+ p->vtime_starttime = 0;
+ p->vtime_state = VTIME_INACTIVE;
#endif

#if defined(SPLIT_RSS_COUNTING)
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -683,10 +683,10 @@ static u64 vtime_delta(struct task_struc
{
unsigned long now = READ_ONCE(jiffies);

- if (time_before(now, (unsigned long)tsk->vtime_snap))
+ if (time_before(now, (unsigned long)tsk->vtime_starttime))
return 0;

- return jiffies_to_nsecs(now - tsk->vtime_snap);
+ return jiffies_to_nsecs(now - tsk->vtime_starttime);
}

static u64 get_vtime_delta(struct task_struct *tsk)
@@ -701,10 +701,10 @@ static u64 get_vtime_delta(struct task_s
* elapsed time. Limit account_other_time to prevent rounding
* errors from causing elapsed vtime to go negative.
*/
- delta = jiffies_to_nsecs(now - tsk->vtime_snap);
+ delta = jiffies_to_nsecs(now - tsk->vtime_starttime);
other = account_other_time(delta);
- WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
- tsk->vtime_snap = now;
+ WARN_ON_ONCE(tsk->vtime_state == VTIME_INACTIVE);
+ tsk->vtime_starttime = now;

return delta - other;
}
@@ -746,7 +746,7 @@ void vtime_guest_enter(struct task_struc
{
/*
* The flags must be updated under the lock with
- * the vtime_snap flush and update.
+ * the vtime_starttime flush and update.
* That enforces a right ordering and update sequence
* synchronization against the reader (task_gtime())
* that can thus safely catch up with a tickless delta.
@@ -776,12 +776,12 @@ void vtime_account_idle(struct task_stru
void arch_vtime_task_switch(struct task_struct *prev)
{
write_seqcount_begin(&prev->vtime_seqcount);
- prev->vtime_snap_whence = VTIME_INACTIVE;
+ prev->vtime_state = VTIME_INACTIVE;
write_seqcount_end(&prev->vtime_seqcount);

write_seqcount_begin(&current->vtime_seqcount);
- current->vtime_snap_whence = VTIME_SYS;
- current->vtime_snap = jiffies;
+ current->vtime_state = VTIME_SYS;
+ current->vtime_starttime = jiffies;
write_seqcount_end(&current->vtime_seqcount);
}

@@ -791,8 +791,8 @@ void vtime_init_idle(struct task_struct

local_irq_save(flags);
write_seqcount_begin(&t->vtime_seqcount);
- t->vtime_snap_whence = VTIME_SYS;
- t->vtime_snap = jiffies;
+ t->vtime_state = VTIME_SYS;
+ t->vtime_starttime = jiffies;
write_seqcount_end(&t->vtime_seqcount);
local_irq_restore(flags);
}
@@ -809,7 +809,7 @@ u64 task_gtime(struct task_struct *t)
seq = read_seqcount_begin(&t->vtime_seqcount);

gtime = t->gtime;
- if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU)
+ if (t->vtime_state == VTIME_SYS && t->flags & PF_VCPU)
gtime += vtime_delta(t);

} while (read_seqcount_retry(&t->vtime_seqcount, seq));
@@ -840,7 +840,7 @@ void task_cputime(struct task_struct *t,
*stime = t->stime;

/* Task is sleeping, nothing to add */
- if (t->vtime_snap_whence == VTIME_INACTIVE || is_idle_task(t))
+ if (t->vtime_state == VTIME_INACTIVE || is_idle_task(t))
continue;

delta = vtime_delta(t);
@@ -849,9 +849,9 @@ void task_cputime(struct task_struct *t,
* Task runs either in user or kernel space, add pending nohz time to
* the right place.
*/
- if (t->vtime_snap_whence == VTIME_USER || t->flags & PF_VCPU)
+ if (t->vtime_state == VTIME_USER || t->flags & PF_VCPU)
*utime += delta;
- else if (t->vtime_snap_whence == VTIME_SYS)
+ else if (t->vtime_state == VTIME_SYS)
*stime += delta;
} while (read_seqcount_retry(&t->vtime_seqcount, seq));
}

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