kernel/context_tracking.c

   1 #include <linux/context_tracking.h>
   2 #include <linux/kvm_host.h>
   3 #include <linux/rcupdate.h>
   4 #include <linux/sched.h>
   5 #include <linux/hardirq.h>
   6 #include <linux/export.h>
   7
   8 DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
   9 #ifdef CONFIG_CONTEXT_TRACKING_FORCE
  10         .active = true,
  11 #endif
  12 };
  13
  14 void user_enter(void)
  15 {
  16         unsigned long flags;
  17
  18         /*
  19          * Some contexts may involve an exception occuring in an irq,
  20          * leading to that nesting:
  21          * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
  22          * This would mess up the dyntick_nesting count though. And rcu_irq_*()
  23          * helpers are enough to protect RCU uses inside the exception. So
  24          * just return immediately if we detect we are in an IRQ.
  25          */
  26         if (in_interrupt())
  27                 return;
  28
  29         WARN_ON_ONCE(!current->mm);
  30
  31         local_irq_save(flags);
  32         if (__this_cpu_read(context_tracking.active) &&
  33             __this_cpu_read(context_tracking.state) != IN_USER) {
  34                 vtime_user_enter(current);
  35                 rcu_user_enter();
  36                 __this_cpu_write(context_tracking.state, IN_USER);
  37         }
  38         local_irq_restore(flags);
  39 }
  40
  41 void user_exit(void)
  42 {
  43         unsigned long flags;
  44
  45         /*
  46          * Some contexts may involve an exception occuring in an irq,
  47          * leading to that nesting:
  48          * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
  49          * This would mess up the dyntick_nesting count though. And rcu_irq_*()
  50          * helpers are enough to protect RCU uses inside the exception. So
  51          * just return immediately if we detect we are in an IRQ.
  52          */
  53         if (in_interrupt())
  54                 return;
  55
  56         local_irq_save(flags);
  57         if (__this_cpu_read(context_tracking.state) == IN_USER) {
  58                 rcu_user_exit();
  59                 vtime_user_exit(current);
  60                 __this_cpu_write(context_tracking.state, IN_KERNEL);
  61         }
  62         local_irq_restore(flags);
  63 }
  64
  65 void guest_enter(void)
  66 {
  67         if (vtime_accounting_enabled())
  68                 vtime_guest_enter(current);
  69         else
  70                 __guest_enter();
  71 }
  72 EXPORT_SYMBOL_GPL(guest_enter);
  73
  74 void guest_exit(void)
  75 {
  76         if (vtime_accounting_enabled())
  77                 vtime_guest_exit(current);
  78         else
  79                 __guest_exit();
  80 }
  81 EXPORT_SYMBOL_GPL(guest_exit);
  82
  83 void context_tracking_task_switch(struct task_struct *prev,
  84                              struct task_struct *next)
  85 {
  86         if (__this_cpu_read(context_tracking.active)) {
  87                 clear_tsk_thread_flag(prev, TIF_NOHZ);
  88                 set_tsk_thread_flag(next, TIF_NOHZ);
  89         }
  90 }