On Mon, Apr 14, 2014 at 09:53:27AM -0700, Joe Perches wrote:
> On Mon, 2014-04-14 at 09:32 -0700, Paul E. McKenney wrote:
> > On Mon, Apr 14, 2014 at 12:19:31PM -0400, Pranith Kumar wrote:
> > > Hi Paul,
> > >
> > > On Mon, Apr 14, 2014 at 12:07 PM, Paul E. McKenney
> > > <paul...@linux.vnet.ibm.com> wrote:
> > > > On Sun, Apr 13, 2014 at 05:53:53PM -0400, Pranith Kumar wrote:
> > > >> remove duplicate definition of extern resched_cpu
> > > >>
> > > >> Signed-off-by: Pranith Kumar <bobby.pr...@gmail.com>
> > > >
> > > > Hello, Pranith,
> > > >
> > > > When I apply this patch I get the following:
> > > >
> > > > /home/paulmck/public_git/linux-rcu/kernel/rcu/tree.c: In function
> > > > ‘rcu_implicit_dynticks_qs’:
> > > > /home/paulmck/public_git/linux-rcu/kernel/rcu/tree.c:895:3: error:
> > > > implicit declaration of function ‘resched_cpu’
> > > > [-Werror=implicit-function-declaration]
> > > > /home/paulmck/public_git/linux-rcu/kernel/rcu/tree.c: At top level:
> > > > /home/paulmck/public_git/linux-rcu/kernel/rcu/tree.c:1009:13: warning:
> > > > conflicting types for ‘resched_cpu’ [enabled by default]
> > > > /home/paulmck/public_git/linux-rcu/kernel/rcu/tree.c:895:3: note:
> > > > previous implicit declaration of ‘resched_cpu’ was here
> > > >
> > > > This failed in under number of different Kconfig setups, the .config
> > > > file
> > > > for one of them is attached.
> > > >
> > > > So this declaration really is needed. Just out of curiosity, what led
> > > > you to believe that it could be removed?
> > > >
> > >
> > > That is strange. The patch removes a duplicate declaration of
> > > resched_cpu (on lines 768, 954) of the file kernel/rcu/tree.c of the
> > > latest git.
> > >
> > > The patch compiles fine here with the latest tip of the git tree.
> > >
> > > CC kernel/rcu/tree.o
> > >
> > > Can you please check if your tree.c has two declarations for resched_cpu?
> >
> > Ah, your patch didn't apply, so I hand-applied it, and removed the first
> > declaration rather than the second one. Trying it again.
>
> Perhaps this might be better than using the extern.
>
> This also would allow the resched_cpu call to become
> static inline as it's very small.
>
> ---
> kernel/rcu/tree.c | 19 +++++++------------
> 1 file changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 0c47e30..7f2c8c2 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -60,6 +60,13 @@
> #include "tree.h"
> #include "rcu.h"
>
> +/*
> + * This include of sched.h (for resched_cpu) really isn't for public
> + * consumption, but RCU is special in that context switches can allow
> + * the state machine to make progress.
> + */
> +#include "../sched/sched.h"
This sort of thing hasn't been well-received recently. Plus the call
to resched_cpu() is very infrequent, so hardly worth the optimization.
Thanx, Paul
> +
> MODULE_ALIAS("rcutree");
> #ifdef MODULE_PARAM_PREFIX
> #undef MODULE_PARAM_PREFIX
> @@ -762,12 +769,6 @@ static int dyntick_save_progress_counter(struct rcu_data
> *rdp,
> }
>
> /*
> - * This function really isn't for public consumption, but RCU is special in
> - * that context switches can allow the state machine to make progress.
> - */
> -extern void resched_cpu(int cpu);
> -
> -/*
> * Return true if the specified CPU has passed through a quiescent
> * state by virtue of being in or having passed through an dynticks
> * idle state since the last call to dyntick_save_progress_counter()
> @@ -947,12 +948,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
> force_quiescent_state(rsp); /* Kick them all. */
> }
>
> -/*
> - * This function really isn't for public consumption, but RCU is special in
> - * that context switches can allow the state machine to make progress.
> - */
> -extern void resched_cpu(int cpu);
> -
> static void print_cpu_stall(struct rcu_state *rsp)
> {
> int cpu;
>
>
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