From 6a61671bb2f3a1bd12cd17b8fca811a624782632 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 16 Dec 2012 20:00:34 +0100 Subject: [PATCH] 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 Cc: Andrew Morton Cc: Ingo Molnar Cc: Li Zhong Cc: Namhyung Kim Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner [fixed kvm module related build errors] Signed-off-by: Sedat Dilek --- arch/s390/kernel/vtime.c | 6 +- include/linux/hardirq.h | 4 +- include/linux/init_task.h | 11 +++ include/linux/kvm_host.h | 20 +++- include/linux/sched.h | 27 +++++- include/linux/vtime.h | 47 +++++----- kernel/context_tracking.c | 21 ++++- kernel/fork.c | 6 ++ kernel/sched/core.c | 1 + kernel/sched/cputime.c | 193 +++++++++++++++++++++++++++++++++++--- kernel/softirq.c | 6 +- 11 files changed, 290 insertions(+), 52 deletions(-) diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index e84b8b68444a..ce9cc5aa2033 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -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) diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 624ef3f45c8e..7105d5cbb762 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -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) diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 6d087c5f57f7..cc898b871cef 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -10,6 +10,7 @@ #include #include #include +#include #include #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) \ } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 4fe2396401da..b7996a768eb2 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -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; diff --git a/include/linux/sched.h b/include/linux/sched.h index a9c608b6154e..a9fa5145e1a7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -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); diff --git a/include/linux/vtime.h b/include/linux/vtime.h index bb50c3ca0d79..71a5782d8c59 100644 --- a/include/linux/vtime.h +++ b/include/linux/vtime.h @@ -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); } diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 9002e92e6372..74f68f4dc6c2 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -1,8 +1,9 @@ #include +#include #include #include #include - +#include 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) { diff --git a/kernel/fork.c b/kernel/fork.c index 65ca6d27f24e..e68a95b4cf26 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -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 diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 257002c13bb0..261022d7e79d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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 diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index a44ecdf809a1..082e05d915b4 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -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 unsigned long long vtime_delta(struct task_struct *tsk) +{ + unsigned long long clock; + + clock = sched_clock(); + if (clock < tsk->vtime_snap) + return 0; -static cputime_t get_vtime_delta(void) + return clock - tsk->vtime_snap; +} + +static cputime_t get_vtime_delta(struct task_struct *tsk) { - unsigned long long delta; + unsigned long long delta = vtime_delta(tsk); - delta = sched_clock() - __this_cpu_read(cputime_snap); - __this_cpu_add(cputime_snap, delta); + 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; + + 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; - delta_cpu = get_vtime_delta(); - account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu)); + 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(¤t->vtime_seqlock); + current->vtime_snap_whence = VTIME_SYS; + current->vtime_snap = sched_clock(); + write_sequnlock(¤t->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 */ diff --git a/kernel/softirq.c b/kernel/softirq.c index ed567babe789..f5cc25f147a6 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -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()) -- 2.20.1