207 lines
6.3 KiB
Diff
207 lines
6.3 KiB
Diff
Subject: vtime: Split lock and seqcount
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Tue, 23 Jul 2013 15:45:51 +0200
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4-rt2.tar.xz
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Replace vtime_seqlock seqlock with a simple seqcounter and a rawlock
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so it can taken in atomic context on RT.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/init_task.h | 3 +-
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include/linux/sched.h | 3 +-
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kernel/fork.c | 3 +-
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kernel/sched/cputime.c | 62 +++++++++++++++++++++++++++++-----------------
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4 files changed, 46 insertions(+), 25 deletions(-)
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--- a/include/linux/init_task.h
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+++ b/include/linux/init_task.h
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@@ -150,7 +150,8 @@ extern struct task_group root_task_group
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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# define INIT_VTIME(tsk) \
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- .vtime_seqlock = __SEQLOCK_UNLOCKED(tsk.vtime_seqlock), \
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+ .vtime_lock = __RAW_SPIN_LOCK_UNLOCKED(tsk.vtime_lock), \
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+ .vtime_seq = SEQCNT_ZERO(tsk.vtime_seq), \
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.vtime_snap = 0, \
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.vtime_snap_whence = VTIME_SYS,
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#else
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -1520,7 +1520,8 @@ struct task_struct {
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cputime_t gtime;
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struct prev_cputime prev_cputime;
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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- seqlock_t vtime_seqlock;
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+ raw_spinlock_t vtime_lock;
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+ seqcount_t vtime_seq;
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unsigned long long vtime_snap;
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enum {
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VTIME_SLEEPING = 0,
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--- a/kernel/fork.c
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+++ b/kernel/fork.c
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@@ -1349,7 +1349,8 @@ static struct task_struct *copy_process(
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prev_cputime_init(&p->prev_cputime);
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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- seqlock_init(&p->vtime_seqlock);
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+ raw_spin_lock_init(&p->vtime_lock);
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+ seqcount_init(&p->vtime_seq);
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p->vtime_snap = 0;
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p->vtime_snap_whence = VTIME_SLEEPING;
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#endif
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--- a/kernel/sched/cputime.c
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+++ b/kernel/sched/cputime.c
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@@ -696,37 +696,45 @@ static void __vtime_account_system(struc
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void vtime_account_system(struct task_struct *tsk)
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{
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- write_seqlock(&tsk->vtime_seqlock);
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+ raw_spin_lock(&tsk->vtime_lock);
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+ write_seqcount_begin(&tsk->vtime_seq);
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__vtime_account_system(tsk);
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- write_sequnlock(&tsk->vtime_seqlock);
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+ write_seqcount_end(&tsk->vtime_seq);
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+ raw_spin_unlock(&tsk->vtime_lock);
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}
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void vtime_gen_account_irq_exit(struct task_struct *tsk)
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{
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- write_seqlock(&tsk->vtime_seqlock);
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+ raw_spin_lock(&tsk->vtime_lock);
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+ write_seqcount_begin(&tsk->vtime_seq);
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__vtime_account_system(tsk);
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if (context_tracking_in_user())
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tsk->vtime_snap_whence = VTIME_USER;
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- write_sequnlock(&tsk->vtime_seqlock);
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+ write_seqcount_end(&tsk->vtime_seq);
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+ raw_spin_unlock(&tsk->vtime_lock);
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}
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void vtime_account_user(struct task_struct *tsk)
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{
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cputime_t delta_cpu;
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- write_seqlock(&tsk->vtime_seqlock);
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+ raw_spin_lock(&tsk->vtime_lock);
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+ write_seqcount_begin(&tsk->vtime_seq);
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delta_cpu = get_vtime_delta(tsk);
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tsk->vtime_snap_whence = VTIME_SYS;
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account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
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- write_sequnlock(&tsk->vtime_seqlock);
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+ write_seqcount_end(&tsk->vtime_seq);
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+ raw_spin_unlock(&tsk->vtime_lock);
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}
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void vtime_user_enter(struct task_struct *tsk)
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{
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- write_seqlock(&tsk->vtime_seqlock);
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+ raw_spin_lock(&tsk->vtime_lock);
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+ write_seqcount_begin(&tsk->vtime_seq);
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__vtime_account_system(tsk);
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tsk->vtime_snap_whence = VTIME_USER;
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- write_sequnlock(&tsk->vtime_seqlock);
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+ write_seqcount_end(&tsk->vtime_seq);
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+ raw_spin_unlock(&tsk->vtime_lock);
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}
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void vtime_guest_enter(struct task_struct *tsk)
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@@ -738,19 +746,23 @@ void vtime_guest_enter(struct task_struc
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* synchronization against the reader (task_gtime())
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* that can thus safely catch up with a tickless delta.
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*/
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- write_seqlock(&tsk->vtime_seqlock);
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+ raw_spin_lock(&tsk->vtime_lock);
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+ write_seqcount_begin(&tsk->vtime_seq);
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__vtime_account_system(tsk);
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current->flags |= PF_VCPU;
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- write_sequnlock(&tsk->vtime_seqlock);
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+ write_seqcount_end(&tsk->vtime_seq);
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+ raw_spin_unlock(&tsk->vtime_lock);
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}
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EXPORT_SYMBOL_GPL(vtime_guest_enter);
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void vtime_guest_exit(struct task_struct *tsk)
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{
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- write_seqlock(&tsk->vtime_seqlock);
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+ raw_spin_lock(&tsk->vtime_lock);
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+ write_seqcount_begin(&tsk->vtime_seq);
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__vtime_account_system(tsk);
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current->flags &= ~PF_VCPU;
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- write_sequnlock(&tsk->vtime_seqlock);
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+ write_seqcount_end(&tsk->vtime_seq);
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+ raw_spin_unlock(&tsk->vtime_lock);
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}
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EXPORT_SYMBOL_GPL(vtime_guest_exit);
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@@ -763,24 +775,30 @@ void vtime_account_idle(struct task_stru
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void arch_vtime_task_switch(struct task_struct *prev)
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{
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- write_seqlock(&prev->vtime_seqlock);
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+ raw_spin_lock(&prev->vtime_lock);
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+ write_seqcount_begin(&prev->vtime_seq);
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prev->vtime_snap_whence = VTIME_SLEEPING;
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- write_sequnlock(&prev->vtime_seqlock);
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+ write_seqcount_end(&prev->vtime_seq);
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+ raw_spin_unlock(&prev->vtime_lock);
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- write_seqlock(¤t->vtime_seqlock);
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+ raw_spin_lock(¤t->vtime_lock);
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+ write_seqcount_begin(¤t->vtime_seq);
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current->vtime_snap_whence = VTIME_SYS;
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current->vtime_snap = sched_clock_cpu(smp_processor_id());
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- write_sequnlock(¤t->vtime_seqlock);
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+ write_seqcount_end(¤t->vtime_seq);
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+ raw_spin_unlock(¤t->vtime_lock);
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}
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void vtime_init_idle(struct task_struct *t, int cpu)
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{
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unsigned long flags;
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- write_seqlock_irqsave(&t->vtime_seqlock, flags);
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+ raw_spin_lock_irqsave(&t->vtime_lock, flags);
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+ write_seqcount_begin(&t->vtime_seq);
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t->vtime_snap_whence = VTIME_SYS;
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t->vtime_snap = sched_clock_cpu(cpu);
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- write_sequnlock_irqrestore(&t->vtime_seqlock, flags);
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+ write_seqcount_end(&t->vtime_seq);
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+ raw_spin_unlock_irqrestore(&t->vtime_lock, flags);
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}
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cputime_t task_gtime(struct task_struct *t)
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@@ -792,13 +810,13 @@ cputime_t task_gtime(struct task_struct
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return t->gtime;
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do {
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- seq = read_seqbegin(&t->vtime_seqlock);
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+ seq = read_seqcount_begin(&t->vtime_seq);
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gtime = t->gtime;
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if (t->flags & PF_VCPU)
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gtime += vtime_delta(t);
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- } while (read_seqretry(&t->vtime_seqlock, seq));
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+ } while (read_seqcount_retry(&t->vtime_seq, seq));
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return gtime;
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}
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@@ -821,7 +839,7 @@ fetch_task_cputime(struct task_struct *t
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*udelta = 0;
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*sdelta = 0;
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- seq = read_seqbegin(&t->vtime_seqlock);
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+ seq = read_seqcount_begin(&t->vtime_seq);
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if (u_dst)
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*u_dst = *u_src;
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@@ -845,7 +863,7 @@ fetch_task_cputime(struct task_struct *t
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if (t->vtime_snap_whence == VTIME_SYS)
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*sdelta = delta;
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}
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- } while (read_seqretry(&t->vtime_seqlock, seq));
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+ } while (read_seqcount_retry(&t->vtime_seq, seq));
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}
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