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Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull NOHZ updates from Thomas Gleixner: "A few updates to the nohz infrastructure: - recursion protection for context tracking - make the TIF_NOHZ inheritance smarter - isolate cpus which belong to the NOHZ full set" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: nohz: Set isolcpus when nohz_full is set nohz: Add tick_nohz_full_add_cpus_to() API context_tracking: Inherit TIF_NOHZ through forks instead of context switches context_tracking: Protect against recursion
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3a95398f54
@ -14,8 +14,6 @@ extern void context_tracking_enter(enum ctx_state state);
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extern void context_tracking_exit(enum ctx_state state);
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extern void context_tracking_user_enter(void);
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extern void context_tracking_user_exit(void);
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extern void __context_tracking_task_switch(struct task_struct *prev,
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struct task_struct *next);
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static inline void user_enter(void)
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{
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@ -51,19 +49,11 @@ static inline void exception_exit(enum ctx_state prev_ctx)
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}
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}
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static inline void context_tracking_task_switch(struct task_struct *prev,
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struct task_struct *next)
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{
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if (context_tracking_is_enabled())
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__context_tracking_task_switch(prev, next);
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}
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#else
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static inline void user_enter(void) { }
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static inline void user_exit(void) { }
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static inline enum ctx_state exception_enter(void) { return 0; }
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static inline void exception_exit(enum ctx_state prev_ctx) { }
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static inline void context_tracking_task_switch(struct task_struct *prev,
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struct task_struct *next) { }
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#endif /* !CONFIG_CONTEXT_TRACKING */
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@ -12,6 +12,7 @@ struct context_tracking {
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* may be further optimized using static keys.
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*/
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bool active;
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int recursion;
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enum ctx_state {
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CONTEXT_KERNEL = 0,
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CONTEXT_USER,
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@ -2599,6 +2599,9 @@ static inline unsigned long wait_task_inactive(struct task_struct *p,
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}
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#endif
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#define tasklist_empty() \
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list_empty(&init_task.tasks)
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#define next_task(p) \
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list_entry_rcu((p)->tasks.next, struct task_struct, tasks)
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@ -134,6 +134,12 @@ static inline bool tick_nohz_full_cpu(int cpu)
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return cpumask_test_cpu(cpu, tick_nohz_full_mask);
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}
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static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
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{
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if (tick_nohz_full_enabled())
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cpumask_or(mask, mask, tick_nohz_full_mask);
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}
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extern void __tick_nohz_full_check(void);
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extern void tick_nohz_full_kick(void);
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extern void tick_nohz_full_kick_cpu(int cpu);
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@ -142,6 +148,7 @@ extern void __tick_nohz_task_switch(struct task_struct *tsk);
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#else
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static inline bool tick_nohz_full_enabled(void) { return false; }
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static inline bool tick_nohz_full_cpu(int cpu) { return false; }
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static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
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static inline void __tick_nohz_full_check(void) { }
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static inline void tick_nohz_full_kick_cpu(int cpu) { }
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static inline void tick_nohz_full_kick(void) { }
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@ -30,12 +30,23 @@ EXPORT_SYMBOL_GPL(context_tracking_enabled);
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DEFINE_PER_CPU(struct context_tracking, context_tracking);
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EXPORT_SYMBOL_GPL(context_tracking);
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void context_tracking_cpu_set(int cpu)
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static bool context_tracking_recursion_enter(void)
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{
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if (!per_cpu(context_tracking.active, cpu)) {
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per_cpu(context_tracking.active, cpu) = true;
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static_key_slow_inc(&context_tracking_enabled);
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int recursion;
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recursion = __this_cpu_inc_return(context_tracking.recursion);
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if (recursion == 1)
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return true;
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WARN_ONCE((recursion < 1), "Invalid context tracking recursion value %d\n", recursion);
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__this_cpu_dec(context_tracking.recursion);
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return false;
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}
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static void context_tracking_recursion_exit(void)
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{
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__this_cpu_dec(context_tracking.recursion);
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}
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/**
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@ -75,6 +86,9 @@ void context_tracking_enter(enum ctx_state state)
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WARN_ON_ONCE(!current->mm);
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local_irq_save(flags);
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if (!context_tracking_recursion_enter())
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goto out_irq_restore;
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if ( __this_cpu_read(context_tracking.state) != state) {
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if (__this_cpu_read(context_tracking.active)) {
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/*
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@ -105,6 +119,8 @@ void context_tracking_enter(enum ctx_state state)
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*/
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__this_cpu_write(context_tracking.state, state);
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}
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context_tracking_recursion_exit();
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out_irq_restore:
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local_irq_restore(flags);
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}
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NOKPROBE_SYMBOL(context_tracking_enter);
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@ -139,6 +155,9 @@ void context_tracking_exit(enum ctx_state state)
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return;
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local_irq_save(flags);
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if (!context_tracking_recursion_enter())
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goto out_irq_restore;
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if (__this_cpu_read(context_tracking.state) == state) {
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if (__this_cpu_read(context_tracking.active)) {
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/*
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@ -153,6 +172,8 @@ void context_tracking_exit(enum ctx_state state)
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}
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__this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
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}
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context_tracking_recursion_exit();
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out_irq_restore:
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local_irq_restore(flags);
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}
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NOKPROBE_SYMBOL(context_tracking_exit);
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@ -164,24 +185,26 @@ void context_tracking_user_exit(void)
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}
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NOKPROBE_SYMBOL(context_tracking_user_exit);
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/**
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* __context_tracking_task_switch - context switch the syscall callbacks
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* @prev: the task that is being switched out
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* @next: the task that is being switched in
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*
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* The context tracking uses the syscall slow path to implement its user-kernel
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* boundaries probes on syscalls. This way it doesn't impact the syscall fast
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* path on CPUs that don't do context tracking.
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*
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* But we need to clear the flag on the previous task because it may later
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* migrate to some CPU that doesn't do the context tracking. As such the TIF
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* flag may not be desired there.
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*/
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void __context_tracking_task_switch(struct task_struct *prev,
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struct task_struct *next)
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void __init context_tracking_cpu_set(int cpu)
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{
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clear_tsk_thread_flag(prev, TIF_NOHZ);
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set_tsk_thread_flag(next, TIF_NOHZ);
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static __initdata bool initialized = false;
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if (!per_cpu(context_tracking.active, cpu)) {
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per_cpu(context_tracking.active, cpu) = true;
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static_key_slow_inc(&context_tracking_enabled);
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}
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if (initialized)
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return;
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/*
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* Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork
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* This assumes that init is the only task at this early boot stage.
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*/
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set_tsk_thread_flag(&init_task, TIF_NOHZ);
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WARN_ON_ONCE(!tasklist_empty());
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initialized = true;
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}
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#ifdef CONFIG_CONTEXT_TRACKING_FORCE
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@ -2374,7 +2374,6 @@ context_switch(struct rq *rq, struct task_struct *prev,
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*/
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spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
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context_tracking_task_switch(prev, next);
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/* Here we just switch the register state and the stack. */
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switch_to(prev, next, prev);
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barrier();
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@ -7068,6 +7067,9 @@ void __init sched_init_smp(void)
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alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
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alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
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/* nohz_full won't take effect without isolating the cpus. */
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tick_nohz_full_add_cpus_to(cpu_isolated_map);
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sched_init_numa();
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/*
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