Re: [PATCH 1/5] rcu,nohz: add state parameter to context_tracking_user_enter/exit

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Fri, Feb 06, 2015 at 11:15:57AM +0100, Paolo Bonzini wrote:
> 
> 
> On 06/02/2015 00:55, Paul E. McKenney wrote:
> > On Thu, Feb 05, 2015 at 03:23:48PM -0500, riel@redhat.com wrote:
> >> From: Rik van Riel <riel@redhat.com>
> >>
> >> Add the expected ctx_state as a parameter to context_tracking_user_enter
> >> and context_tracking_user_exit, allowing the same functions to not just
> >> track kernel <> user space switching, but also kernel <> guest transitions.
> >>
> >> Signed-off-by: Rik van Riel <riel@redhat.com>
> > 
> > Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> /me wonders: whose tree is supposed to carry these patches?

If no one else does, I would be happy to.  I would be thinking in terms
of 3.21, in other words, not the merge window starting in three days,
but the one after that.

							Thanx, Paul

> Paolo
> 
> >> ---
> >>  include/linux/context_tracking.h | 12 ++++++------
> >>  kernel/context_tracking.c        | 10 +++++-----
> >>  2 files changed, 11 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> >> index 37b81bd51ec0..bd9f000fc98d 100644
> >> --- a/include/linux/context_tracking.h
> >> +++ b/include/linux/context_tracking.h
> >> @@ -10,21 +10,21 @@
> >>  #ifdef CONFIG_CONTEXT_TRACKING
> >>  extern void context_tracking_cpu_set(int cpu);
> >>
> >> -extern void context_tracking_user_enter(void);
> >> -extern void context_tracking_user_exit(void);
> >> +extern void context_tracking_user_enter(enum ctx_state state);
> >> +extern void context_tracking_user_exit(enum ctx_state state);
> >>  extern void __context_tracking_task_switch(struct task_struct *prev,
> >>  					   struct task_struct *next);
> >>
> >>  static inline void user_enter(void)
> >>  {
> >>  	if (context_tracking_is_enabled())
> >> -		context_tracking_user_enter();
> >> +		context_tracking_user_enter(IN_USER);
> >>
> >>  }
> >>  static inline void user_exit(void)
> >>  {
> >>  	if (context_tracking_is_enabled())
> >> -		context_tracking_user_exit();
> >> +		context_tracking_user_exit(IN_USER);
> >>  }
> >>
> >>  static inline enum ctx_state exception_enter(void)
> >> @@ -35,7 +35,7 @@ static inline enum ctx_state exception_enter(void)
> >>  		return 0;
> >>
> >>  	prev_ctx = this_cpu_read(context_tracking.state);
> >> -	context_tracking_user_exit();
> >> +	context_tracking_user_exit(prev_ctx);
> >>
> >>  	return prev_ctx;
> >>  }
> >> @@ -44,7 +44,7 @@ static inline void exception_exit(enum ctx_state prev_ctx)
> >>  {
> >>  	if (context_tracking_is_enabled()) {
> >>  		if (prev_ctx == IN_USER)
> >> -			context_tracking_user_enter();
> >> +			context_tracking_user_enter(prev_ctx);
> >>  	}
> >>  }
> >>
> >> diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
> >> index 937ecdfdf258..4c010787c9ec 100644
> >> --- a/kernel/context_tracking.c
> >> +++ b/kernel/context_tracking.c
> >> @@ -47,7 +47,7 @@ void context_tracking_cpu_set(int cpu)
> >>   * to execute won't use any RCU read side critical section because this
> >>   * function sets RCU in extended quiescent state.
> >>   */
> >> -void context_tracking_user_enter(void)
> >> +void context_tracking_user_enter(enum ctx_state state)
> >>  {
> >>  	unsigned long flags;
> >>
> >> @@ -75,7 +75,7 @@ void context_tracking_user_enter(void)
> >>  	WARN_ON_ONCE(!current->mm);
> >>
> >>  	local_irq_save(flags);
> >> -	if ( __this_cpu_read(context_tracking.state) != IN_USER) {
> >> +	if ( __this_cpu_read(context_tracking.state) != state) {
> >>  		if (__this_cpu_read(context_tracking.active)) {
> >>  			trace_user_enter(0);
> >>  			/*
> >> @@ -101,7 +101,7 @@ void context_tracking_user_enter(void)
> >>  		 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
> >>  		 * is false because we know that CPU is not tickless.
> >>  		 */
> >> -		__this_cpu_write(context_tracking.state, IN_USER);
> >> +		__this_cpu_write(context_tracking.state, state);
> >>  	}
> >>  	local_irq_restore(flags);
> >>  }
> >> @@ -118,7 +118,7 @@ NOKPROBE_SYMBOL(context_tracking_user_enter);
> >>   * This call supports re-entrancy. This way it can be called from any exception
> >>   * handler without needing to know if we came from userspace or not.
> >>   */
> >> -void context_tracking_user_exit(void)
> >> +void context_tracking_user_exit(enum ctx_state state)
> >>  {
> >>  	unsigned long flags;
> >>
> >> @@ -129,7 +129,7 @@ void context_tracking_user_exit(void)
> >>  		return;
> >>
> >>  	local_irq_save(flags);
> >> -	if (__this_cpu_read(context_tracking.state) == IN_USER) {
> >> +	if (__this_cpu_read(context_tracking.state) == state) {
> >>  		if (__this_cpu_read(context_tracking.active)) {
> >>  			/*
> >>  			 * We are going to run code that may use RCU. Inform
> >> -- 
> >> 1.9.3
> >>
> > 
>