84 lines
2.1 KiB
C
84 lines
2.1 KiB
C
#include <linux/context_tracking.h>
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#include <linux/rcupdate.h>
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#include <linux/sched.h>
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#include <linux/percpu.h>
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#include <linux/hardirq.h>
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struct context_tracking {
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/*
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* When active is false, hooks are not set to
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* minimize overhead: TIF flags are cleared
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* and calls to user_enter/exit are ignored. This
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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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enum {
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IN_KERNEL = 0,
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IN_USER,
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} state;
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};
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static DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
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#ifdef CONFIG_CONTEXT_TRACKING_FORCE
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.active = true,
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#endif
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};
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void user_enter(void)
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{
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unsigned long flags;
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/*
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* Some contexts may involve an exception occuring in an irq,
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* leading to that nesting:
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* rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
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* This would mess up the dyntick_nesting count though. And rcu_irq_*()
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* helpers are enough to protect RCU uses inside the exception. So
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* just return immediately if we detect we are in an IRQ.
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*/
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if (in_interrupt())
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return;
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WARN_ON_ONCE(!current->mm);
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local_irq_save(flags);
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if (__this_cpu_read(context_tracking.active) &&
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__this_cpu_read(context_tracking.state) != IN_USER) {
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__this_cpu_write(context_tracking.state, IN_USER);
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rcu_user_enter();
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}
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local_irq_restore(flags);
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}
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void user_exit(void)
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{
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unsigned long flags;
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/*
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* Some contexts may involve an exception occuring in an irq,
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* leading to that nesting:
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* rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
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* This would mess up the dyntick_nesting count though. And rcu_irq_*()
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* helpers are enough to protect RCU uses inside the exception. So
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* just return immediately if we detect we are in an IRQ.
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*/
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if (in_interrupt())
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return;
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local_irq_save(flags);
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if (__this_cpu_read(context_tracking.state) == IN_USER) {
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__this_cpu_write(context_tracking.state, IN_KERNEL);
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rcu_user_exit();
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}
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local_irq_restore(flags);
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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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{
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if (__this_cpu_read(context_tracking.active)) {
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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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}
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}
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