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cputime: Safely read cputime of full dynticks CPUs 

While remotely reading the cputime of a task running in a
full dynticks CPU, the values stored in utime/stime fields
of struct task_struct may be stale. Its values may be those
of the last kernel <-> user transition time snapshot and
we need to add the tickless time spent since this snapshot.

To fix this, flush the cputime of the dynticks CPUs on
kernel <-> user transition and record the time / context
where we did this. Then on top of this snapshot and the current
time, perform the fixup on the reader side from task_times()
accessors.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[fixed kvm module related build errors]
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
This commit is contained in:
Frederic Weisbecker 2012-12-16 20:00:34 +01:00
parent c11f11fcbd
commit 6a61671bb2
11 changed files with 292 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/s390/kernel/vtime.c
View File

@ -127,7 +127,7 @@ void vtime_account_user(struct task_struct *tsk)
* Update process times based on virtual cpu times stored by entry.S
* to the lowcore fields user_timer, system_timer & steal_clock.
*/
void vtime_account(struct task_struct *tsk)
void vtime_account_irq_enter(struct task_struct *tsk)
{
struct thread_info *ti = task_thread_info(tsk);
u64 timer, system;
@ -145,10 +145,10 @@ void vtime_account(struct task_struct *tsk)
virt_timer_forward(system);
}
EXPORT_SYMBOL_GPL(vtime_account);
EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
void vtime_account_system(struct task_struct *tsk)
__attribute__((alias("vtime_account")));
__attribute__((alias("vtime_account_irq_enter")));
EXPORT_SYMBOL_GPL(vtime_account_system);
void __kprobes vtime_stop_cpu(void)

4
include/linux/hardirq.h
View File

@ -153,7 +153,7 @@ extern void rcu_nmi_exit(void);
*/
#define __irq_enter() \
do { \
vtime_account_irq_enter(current); \
account_irq_enter_time(current); \
add_preempt_count(HARDIRQ_OFFSET); \
trace_hardirq_enter(); \
} while (0)
@ -169,7 +169,7 @@ extern void irq_enter(void);
#define __irq_exit() \
do { \
trace_hardirq_exit(); \
vtime_account_irq_exit(current); \
account_irq_exit_time(current); \
sub_preempt_count(HARDIRQ_OFFSET); \
} while (0)

11
include/linux/init_task.h
View File

@ -10,6 +10,7 @@
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/securebits.h>
#include <linux/seqlock.h>
#include <net/net_namespace.h>
#ifdef CONFIG_SMP
@ -141,6 +142,15 @@ extern struct task_group root_task_group;
# define INIT_PERF_EVENTS(tsk)
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
# define INIT_VTIME(tsk) \
.vtime_seqlock = __SEQLOCK_UNLOCKED(tsk.vtime_seqlock), \
.vtime_snap = 0, \
.vtime_snap_whence = VTIME_SYS,
#else
# define INIT_VTIME(tsk)
#endif
#define INIT_TASK_COMM "swapper"
/*
@ -210,6 +220,7 @@ extern struct task_group root_task_group;
INIT_TRACE_RECURSION \
INIT_TASK_RCU_PREEMPT(tsk) \
INIT_CPUSET_SEQ \
INIT_VTIME(tsk) \
}

20
include/linux/kvm_host.h
View File

@ -741,7 +741,7 @@ static inline int kvm_deassign_device(struct kvm *kvm,
}
#endif /* CONFIG_IOMMU_API */
static inline void guest_enter(void)
static inline void __guest_enter(void)
{
/*
* This is running in ioctl context so we can avoid
@ -751,7 +751,7 @@ static inline void guest_enter(void)
current->flags |= PF_VCPU;
}
static inline void guest_exit(void)
static inline void __guest_exit(void)
{
/*
* This is running in ioctl context so we can avoid
@ -761,6 +761,22 @@ static inline void guest_exit(void)
current->flags &= ~PF_VCPU;
}
#ifdef CONFIG_CONTEXT_TRACKING
extern void guest_enter(void);
extern void guest_exit(void);
#else /* !CONFIG_CONTEXT_TRACKING */
static inline void guest_enter(void)
{
__guest_enter();
}
static inline void guest_exit(void)
{
__guest_exit();
}
#endif /* !CONFIG_CONTEXT_TRACKING */
static inline void kvm_guest_enter(void)
{
unsigned long flags;

27
include/linux/sched.h
View File

@ -1367,6 +1367,15 @@ struct task_struct {
cputime_t gtime;
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
struct cputime prev_cputime;
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqlock_t vtime_seqlock;
unsigned long long vtime_snap;
enum {
VTIME_SLEEPING = 0,
VTIME_USER,
VTIME_SYS,
} vtime_snap_whence;
#endif
unsigned long nvcsw, nivcsw; /* context switch counts */
struct timespec start_time; /* monotonic time */
@ -1792,11 +1801,13 @@ static inline void put_task_struct(struct task_struct *t)
__put_task_struct(t);
}
static inline cputime_t task_gtime(struct task_struct *t)
{
return t->gtime;
}
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
extern void task_cputime(struct task_struct *t,
cputime_t *utime, cputime_t *stime);
extern void task_cputime_scaled(struct task_struct *t,
cputime_t *utimescaled, cputime_t *stimescaled);
extern cputime_t task_gtime(struct task_struct *t);
#else
static inline void task_cputime(struct task_struct *t,
cputime_t *utime, cputime_t *stime)
{
@ -1815,6 +1826,12 @@ static inline void task_cputime_scaled(struct task_struct *t,
if (stimescaled)
*stimescaled = t->stimescaled;
}
static inline cputime_t task_gtime(struct task_struct *t)
{
return t->gtime;
}
#endif
extern void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st);
extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st);

47
include/linux/vtime.h
View File

@ -8,35 +8,44 @@ extern void vtime_task_switch(struct task_struct *prev);
extern void vtime_account_system(struct task_struct *tsk);
extern void vtime_account_idle(struct task_struct *tsk);
extern void vtime_account_user(struct task_struct *tsk);
extern void vtime_account(struct task_struct *tsk);
extern void vtime_account_irq_enter(struct task_struct *tsk);
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
extern bool vtime_accounting_enabled(void);
#else
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
static inline bool vtime_accounting_enabled(void) { return true; }
#endif
#else /* !CONFIG_VIRT_CPU_ACCOUNTING */
static inline void vtime_task_switch(struct task_struct *prev) { }
static inline void vtime_account_system(struct task_struct *tsk) { }
static inline void vtime_account_user(struct task_struct *tsk) { }
static inline void vtime_account(struct task_struct *tsk) { }
static inline void vtime_account_irq_enter(struct task_struct *tsk) { }
static inline bool vtime_accounting_enabled(void) { return false; }
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
static inline void arch_vtime_task_switch(struct task_struct *tsk) { }
static inline void vtime_user_enter(struct task_struct *tsk)
{
vtime_account_system(tsk);
}
extern void arch_vtime_task_switch(struct task_struct *tsk);
extern void vtime_account_irq_exit(struct task_struct *tsk);
extern bool vtime_accounting_enabled(void);
extern void vtime_user_enter(struct task_struct *tsk);
static inline void vtime_user_exit(struct task_struct *tsk)
{
vtime_account_user(tsk);
}
extern void vtime_guest_enter(struct task_struct *tsk);
extern void vtime_guest_exit(struct task_struct *tsk);
extern void vtime_init_idle(struct task_struct *tsk);
#else
static inline void vtime_account_irq_exit(struct task_struct *tsk)
{
/* On hard|softirq exit we always account to hard|softirq cputime */
vtime_account_system(tsk);
}
static inline void vtime_user_enter(struct task_struct *tsk) { }
static inline void vtime_user_exit(struct task_struct *tsk) { }
static inline void vtime_guest_enter(struct task_struct *tsk) { }
static inline void vtime_guest_exit(struct task_struct *tsk) { }
static inline void vtime_init_idle(struct task_struct *tsk) { }
#endif
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
@ -45,25 +54,15 @@ extern void irqtime_account_irq(struct task_struct *tsk);
static inline void irqtime_account_irq(struct task_struct *tsk) { }
#endif
static inline void vtime_account_irq_enter(struct task_struct *tsk)
static inline void account_irq_enter_time(struct task_struct *tsk)
{
/*
* Hardirq can interrupt idle task anytime. So we need vtime_account()
* that performs the idle check in CONFIG_VIRT_CPU_ACCOUNTING.
* Softirq can also interrupt idle task directly if it calls
* local_bh_enable(). Such case probably don't exist but we never know.
* Ksoftirqd is not concerned because idle time is flushed on context
* switch. Softirqs in the end of hardirqs are also not a problem because
* the idle time is flushed on hardirq time already.
*/
vtime_account(tsk);
vtime_account_irq_enter(tsk);
irqtime_account_irq(tsk);
}
static inline void vtime_account_irq_exit(struct task_struct *tsk)
static inline void account_irq_exit_time(struct task_struct *tsk)
{
/* On hard|softirq exit we always account to hard|softirq cputime */
vtime_account_system(tsk);
vtime_account_irq_exit(tsk);
irqtime_account_irq(tsk);
}

21
kernel/context_tracking.c
View File

@ -1,8 +1,9 @@
#include <linux/context_tracking.h>
#include <linux/kvm_host.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/hardirq.h>
#include <linux/export.h>
DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
#ifdef CONFIG_CONTEXT_TRACKING_FORCE
@ -61,6 +62,24 @@ void user_exit(void)
local_irq_restore(flags);
}
void guest_enter(void)
{
if (vtime_accounting_enabled())
vtime_guest_enter(current);
else
__guest_enter();
}
EXPORT_SYMBOL_GPL(guest_enter);
void guest_exit(void)
{
if (vtime_accounting_enabled())
vtime_guest_exit(current);
else
__guest_exit();
}
EXPORT_SYMBOL_GPL(guest_exit);
void context_tracking_task_switch(struct task_struct *prev,
struct task_struct *next)
{

6
kernel/fork.c
View File

@ -1233,6 +1233,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
p->prev_cputime.utime = p->prev_cputime.stime = 0;
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
seqlock_init(&p->vtime_seqlock);
p->vtime_snap = 0;
p->vtime_snap_whence = VTIME_SLEEPING;
#endif
#if defined(SPLIT_RSS_COUNTING)
memset(&p->rss_stat, 0, sizeof(p->rss_stat));
#endif

1
kernel/sched/core.c
View File

@ -4666,6 +4666,7 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu)
*/
idle->sched_class = &idle_sched_class;
ftrace_graph_init_idle_task(idle, cpu);
vtime_init_idle(idle);
#if defined(CONFIG_SMP)
sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
#endif

197
kernel/sched/cputime.c
View File

@ -492,7 +492,7 @@ void vtime_task_switch(struct task_struct *prev)
* vtime_account().
*/
#ifndef __ARCH_HAS_VTIME_ACCOUNT
void vtime_account(struct task_struct *tsk)
void vtime_account_irq_enter(struct task_struct *tsk)
{
if (!vtime_accounting_enabled())
return;
@ -516,7 +516,7 @@ void vtime_account(struct task_struct *tsk)
}
vtime_account_system(tsk);
}
EXPORT_SYMBOL_GPL(vtime_account);
EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
#endif /* __ARCH_HAS_VTIME_ACCOUNT */
#else /* !CONFIG_VIRT_CPU_ACCOUNTING */
@ -600,28 +600,55 @@ void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime
#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
static DEFINE_PER_CPU(unsigned long long, cputime_snap);
static cputime_t get_vtime_delta(void)
static unsigned long long vtime_delta(struct task_struct *tsk)
{
unsigned long long delta;
unsigned long long clock;
delta = sched_clock() - __this_cpu_read(cputime_snap);
__this_cpu_add(cputime_snap, delta);
clock = sched_clock();
if (clock < tsk->vtime_snap)
return 0;
return clock - tsk->vtime_snap;
}
static cputime_t get_vtime_delta(struct task_struct *tsk)
{
unsigned long long delta = vtime_delta(tsk);
WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_SLEEPING);
tsk->vtime_snap += delta;
/* CHECKME: always safe to convert nsecs to cputime? */
return nsecs_to_cputime(delta);
}
static void __vtime_account_system(struct task_struct *tsk)
{
cputime_t delta_cpu = get_vtime_delta(tsk);
account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
}
void vtime_account_system(struct task_struct *tsk)
{
cputime_t delta_cpu;
if (!vtime_accounting_enabled())
return;
delta_cpu = get_vtime_delta();
account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
write_seqlock(&tsk->vtime_seqlock);
__vtime_account_system(tsk);
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_account_irq_exit(struct task_struct *tsk)
{
if (!vtime_accounting_enabled())
return;
write_seqlock(&tsk->vtime_seqlock);
if (context_tracking_in_user())
tsk->vtime_snap_whence = VTIME_USER;
__vtime_account_system(tsk);
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_account_user(struct task_struct *tsk)
@ -631,14 +658,44 @@ void vtime_account_user(struct task_struct *tsk)
if (!vtime_accounting_enabled())
return;
delta_cpu = get_vtime_delta();
delta_cpu = get_vtime_delta(tsk);
write_seqlock(&tsk->vtime_seqlock);
tsk->vtime_snap_whence = VTIME_SYS;
account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_user_enter(struct task_struct *tsk)
{
if (!vtime_accounting_enabled())
return;
write_seqlock(&tsk->vtime_seqlock);
tsk->vtime_snap_whence = VTIME_USER;
__vtime_account_system(tsk);
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_guest_enter(struct task_struct *tsk)
{
write_seqlock(&tsk->vtime_seqlock);
__vtime_account_system(tsk);
current->flags |= PF_VCPU;
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_guest_exit(struct task_struct *tsk)
{
write_seqlock(&tsk->vtime_seqlock);
__vtime_account_system(tsk);
current->flags &= ~PF_VCPU;
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_account_idle(struct task_struct *tsk)
{
cputime_t delta_cpu = get_vtime_delta();
cputime_t delta_cpu = get_vtime_delta(tsk);
account_idle_time(delta_cpu);
}
@ -647,4 +704,116 @@ bool vtime_accounting_enabled(void)
{
return context_tracking_active();
}
void arch_vtime_task_switch(struct task_struct *prev)
{
write_seqlock(&prev->vtime_seqlock);
prev->vtime_snap_whence = VTIME_SLEEPING;
write_sequnlock(&prev->vtime_seqlock);
write_seqlock(&current->vtime_seqlock);
current->vtime_snap_whence = VTIME_SYS;
current->vtime_snap = sched_clock();
write_sequnlock(&current->vtime_seqlock);
}
void vtime_init_idle(struct task_struct *t)
{
unsigned long flags;
write_seqlock_irqsave(&t->vtime_seqlock, flags);
t->vtime_snap_whence = VTIME_SYS;
t->vtime_snap = sched_clock();
write_sequnlock_irqrestore(&t->vtime_seqlock, flags);
}
cputime_t task_gtime(struct task_struct *t)
{
unsigned long flags;
unsigned int seq;
cputime_t gtime;
do {
seq = read_seqbegin_irqsave(&t->vtime_seqlock, flags);
gtime = t->gtime;
if (t->flags & PF_VCPU)
gtime += vtime_delta(t);
} while (read_seqretry_irqrestore(&t->vtime_seqlock, seq, flags));
return gtime;
}
/*
* Fetch cputime raw values from fields of task_struct and
* add up the pending nohz execution time since the last
* cputime snapshot.
*/
static void
fetch_task_cputime(struct task_struct *t,
cputime_t *u_dst, cputime_t *s_dst,
cputime_t *u_src, cputime_t *s_src,
cputime_t *udelta, cputime_t *sdelta)
{
unsigned long flags;
unsigned int seq;
unsigned long long delta;
do {
*udelta = 0;
*sdelta = 0;
seq = read_seqbegin_irqsave(&t->vtime_seqlock, flags);
if (u_dst)
*u_dst = *u_src;
if (s_dst)
*s_dst = *s_src;
/* Task is sleeping, nothing to add */
if (t->vtime_snap_whence == VTIME_SLEEPING ||
is_idle_task(t))
continue;
delta = vtime_delta(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) {
*udelta = delta;
} else {
if (t->vtime_snap_whence == VTIME_SYS)
*sdelta = delta;
}
} while (read_seqretry_irqrestore(&t->vtime_seqlock, seq, flags));
}
void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime)
{
cputime_t udelta, sdelta;
fetch_task_cputime(t, utime, stime, &t->utime,
&t->stime, &udelta, &sdelta);
if (utime)
*utime += udelta;
if (stime)
*stime += sdelta;
}
void task_cputime_scaled(struct task_struct *t,
cputime_t *utimescaled, cputime_t *stimescaled)
{
cputime_t udelta, sdelta;
fetch_task_cputime(t, utimescaled, stimescaled,
&t->utimescaled, &t->stimescaled, &udelta, &sdelta);
if (utimescaled)
*utimescaled += cputime_to_scaled(udelta);
if (stimescaled)
*stimescaled += cputime_to_scaled(sdelta);
}
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */

6
kernel/softirq.c
View File

@ -221,7 +221,7 @@ asmlinkage void __do_softirq(void)
current->flags &= ~PF_MEMALLOC;
pending = local_softirq_pending();
vtime_account_irq_enter(current);
account_irq_enter_time(current);
__local_bh_disable((unsigned long)__builtin_return_address(0),
SOFTIRQ_OFFSET);
@ -272,7 +272,7 @@ restart:
lockdep_softirq_exit();
vtime_account_irq_exit(current);
account_irq_exit_time(current);
__local_bh_enable(SOFTIRQ_OFFSET);
tsk_restore_flags(current, old_flags, PF_MEMALLOC);
}
@ -341,7 +341,7 @@ static inline void invoke_softirq(void)
*/
void irq_exit(void)
{
vtime_account_irq_exit(current);
account_irq_exit_time(current);
trace_hardirq_exit();
sub_preempt_count(IRQ_EXIT_OFFSET);
if (!in_interrupt() && local_softirq_pending())