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# include <linux/context_tracking.h>
# include <linux/rcupdate.h>
# include <linux/sched.h>
# include <linux/hardirq.h>
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DEFINE_PER_CPU ( struct context_tracking , context_tracking ) = {
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# ifdef CONFIG_CONTEXT_TRACKING_FORCE
. active = true ,
# endif
} ;
void user_enter ( void )
{
unsigned long flags ;
/*
* Some contexts may involve an exception occuring in an irq ,
* leading to that nesting :
* rcu_irq_enter ( ) rcu_user_exit ( ) rcu_user_exit ( ) rcu_irq_exit ( )
* This would mess up the dyntick_nesting count though . And rcu_irq_ * ( )
* helpers are enough to protect RCU uses inside the exception . So
* just return immediately if we detect we are in an IRQ .
*/
if ( in_interrupt ( ) )
return ;
WARN_ON_ONCE ( ! current - > mm ) ;
local_irq_save ( flags ) ;
if ( __this_cpu_read ( context_tracking . active ) & &
__this_cpu_read ( context_tracking . state ) ! = IN_USER ) {
__this_cpu_write ( context_tracking . state , IN_USER ) ;
rcu_user_enter ( ) ;
}
local_irq_restore ( flags ) ;
}
void user_exit ( void )
{
unsigned long flags ;
/*
* Some contexts may involve an exception occuring in an irq ,
* leading to that nesting :
* rcu_irq_enter ( ) rcu_user_exit ( ) rcu_user_exit ( ) rcu_irq_exit ( )
* This would mess up the dyntick_nesting count though . And rcu_irq_ * ( )
* helpers are enough to protect RCU uses inside the exception . So
* just return immediately if we detect we are in an IRQ .
*/
if ( in_interrupt ( ) )
return ;
local_irq_save ( flags ) ;
if ( __this_cpu_read ( context_tracking . state ) = = IN_USER ) {
__this_cpu_write ( context_tracking . state , IN_KERNEL ) ;
rcu_user_exit ( ) ;
}
local_irq_restore ( flags ) ;
}
void context_tracking_task_switch ( struct task_struct * prev ,
struct task_struct * next )
{
if ( __this_cpu_read ( context_tracking . active ) ) {
clear_tsk_thread_flag ( prev , TIF_NOHZ ) ;
set_tsk_thread_flag ( next , TIF_NOHZ ) ;
}
}