On Wed, May 13, 2015 at 10:45:05AM -0700, Paul E. McKenney wrote:
> On Wed, May 13, 2015 at 02:37:52AM +0200, Frederic Weisbecker wrote:
> > On Tue, May 12, 2015 at 03:30:45PM -0700, Paul E. McKenney wrote:
> > > From: "Paul E. McKenney" <[email protected]>
> > >
> > > Currently, Kconfig will ask the user whether RCU_USER_QS should be set.
> > > This is silly because Kconfig already has all the information that it
> > > needs to set this parameter. This commit therefore directly drives
> > > the value of RCU_USER_QS via NO_HZ_FULL's "select" statement.
> > >
> > > Reported-by: Ingo Molnar <[email protected]>
> > > Signed-off-by: Paul E. McKenney <[email protected]>
> > > Cc: Frederic Weisbecker <[email protected]>
> >
> > ACK. And we should remove it completely and use NO_HZ_FULL instead.
> > There won't seem to be more users.
>
> Good point! I have queued the patch shown below for 4.3.
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> rcu: Drop RCU_USER_QS in favor of NO_HZ_FULL
>
> The RCU_USER_QS Kconfig parameter is now just a synonym for NO_HZ_FULL,
> so this commit eliminates RCU_USER_QS, replacing all uses with NO_HZ_FULL.
>
> Reported-by: Frederic Weisbecker <[email protected]>
> Signed-off-by: Paul E. McKenney <[email protected]>
Excellent! ACK+!
Thanks.
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 03a899aabd17..18e377b92875 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -307,7 +307,7 @@ static inline void rcu_sysrq_end(void)
> }
> #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
>
> -#ifdef CONFIG_RCU_USER_QS
> +#ifdef CONFIG_NO_HZ_FULL
> void rcu_user_enter(void);
> void rcu_user_exit(void);
> #else
> @@ -315,7 +315,7 @@ static inline void rcu_user_enter(void) { }
> static inline void rcu_user_exit(void) { }
> static inline void rcu_user_hooks_switch(struct task_struct *prev,
> struct task_struct *next) { }
> -#endif /* CONFIG_RCU_USER_QS */
> +#endif /* CONFIG_NO_HZ_FULL */
>
> #ifdef CONFIG_RCU_NOCB_CPU
> void rcu_init_nohz(void);
> diff --git a/init/Kconfig b/init/Kconfig
> index 4c08197044f1..5b8726c10685 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -537,15 +537,6 @@ config RCU_STALL_COMMON
> config CONTEXT_TRACKING
> bool
>
> -config RCU_USER_QS
> - bool
> - help
> - This option sets hooks on kernel / userspace boundaries and
> - puts RCU in extended quiescent state when the CPU runs in
> - userspace. It means that when a CPU runs in userspace, it is
> - excluded from the global RCU state machine and thus doesn't
> - try to keep the timer tick on for RCU.
> -
> config CONTEXT_TRACKING_FORCE
> bool "Force context tracking"
> depends on CONTEXT_TRACKING
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 7651d7dd982c..012cbee9d354 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -696,7 +696,7 @@ void rcu_idle_enter(void)
> }
> EXPORT_SYMBOL_GPL(rcu_idle_enter);
>
> -#ifdef CONFIG_RCU_USER_QS
> +#ifdef CONFIG_NO_HZ_FULL
> /**
> * rcu_user_enter - inform RCU that we are resuming userspace.
> *
> @@ -709,7 +709,7 @@ void rcu_user_enter(void)
> {
> rcu_eqs_enter(1);
> }
> -#endif /* CONFIG_RCU_USER_QS */
> +#endif /* CONFIG_NO_HZ_FULL */
>
> /**
> * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
> @@ -823,7 +823,7 @@ void rcu_idle_exit(void)
> }
> EXPORT_SYMBOL_GPL(rcu_idle_exit);
>
> -#ifdef CONFIG_RCU_USER_QS
> +#ifdef CONFIG_NO_HZ_FULL
> /**
> * rcu_user_exit - inform RCU that we are exiting userspace.
> *
> @@ -834,7 +834,7 @@ void rcu_user_exit(void)
> {
> rcu_eqs_exit(1);
> }
> -#endif /* CONFIG_RCU_USER_QS */
> +#endif /* CONFIG_NO_HZ_FULL */
>
> /**
> * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> index 579ce1b929af..4008d9f95dd7 100644
> --- a/kernel/time/Kconfig
> +++ b/kernel/time/Kconfig
> @@ -92,12 +92,10 @@ config NO_HZ_FULL
> depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
> # We need at least one periodic CPU for timekeeping
> depends on SMP
> - # RCU_USER_QS dependency
> depends on HAVE_CONTEXT_TRACKING
> # VIRT_CPU_ACCOUNTING_GEN dependency
> depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
> select NO_HZ_COMMON
> - select RCU_USER_QS
> select RCU_NOCB_CPU
> select VIRT_CPU_ACCOUNTING_GEN
> select IRQ_WORK
>
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