On Tue, May 21, 2013 at 10:31:41AM -0700, Josh Triplett wrote:
> On Mon, May 20, 2013 at 07:58:20AM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <[email protected]>
> >
> > TINY_RCU's reset_cpu_stall_ticks() and check_cpu_stalls() functions
> > are defined unconditionally, and are empty functions if CONFIG_RCU_TRACE
> > is disabled (which in turns disables detection of RCU CPU stalls).
> > These empty functions can add a bit of bloat to TINY_RCU, so this
> > commit reworks the ifdefs so that these functions are defined only
> > if they actually do something.
> >
> > Signed-off-by: Paul E. McKenney <[email protected]>
>
> Strange. Both of these functions are static, and called in only one
> place, so shouldn't the compiler inline them (and thus throw them away
> completely when empty)? Why does it not do so?
Good point for most architectures. But given Tiny RCU's purpose, it
should allow for stupid compilers. And I do need to fix the commit
message to call out the other benefit, namely saving a couple of
lines of source code.
Thanx, Paul
> - Josh Triplett
>
> > ---
> > kernel/rcutiny.c | 4 ++--
> > kernel/rcutiny_plugin.h | 6 ++----
> > 2 files changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
> > index 4adc9e2..aa34411 100644
> > --- a/kernel/rcutiny.c
> > +++ b/kernel/rcutiny.c
> > @@ -204,7 +204,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
> > */
> > static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
> > {
> > - reset_cpu_stall_ticks(rcp);
> > + RCU_TRACE(reset_cpu_stall_ticks(rcp));
> > if (rcp->rcucblist != NULL &&
> > rcp->donetail != rcp->curtail) {
> > rcp->donetail = rcp->curtail;
> > @@ -251,7 +251,7 @@ void rcu_bh_qs(int cpu)
> > */
> > void rcu_check_callbacks(int cpu, int user)
> > {
> > - check_cpu_stalls();
> > + RCU_TRACE(check_cpu_stalls());
> > if (user || rcu_is_cpu_rrupt_from_idle())
> > rcu_sched_qs(cpu);
> > else if (!in_softirq())
> > diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
> > index 65ef180..0cd385a 100644
> > --- a/kernel/rcutiny_plugin.h
> > +++ b/kernel/rcutiny_plugin.h
> > @@ -158,15 +158,11 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
> > rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
> > }
> >
> > -#endif /* #ifdef CONFIG_RCU_TRACE */
> > -
> > static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
> > {
> > -#ifdef CONFIG_RCU_TRACE
> > rcp->ticks_this_gp = 0;
> > rcp->gp_start = jiffies;
> > rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
> > -#endif /* #ifdef CONFIG_RCU_TRACE */
> > }
> >
> > static void check_cpu_stalls(void)
> > @@ -174,3 +170,5 @@ static void check_cpu_stalls(void)
> > RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
> > RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
> > }
> > +
> > +#endif /* #ifdef CONFIG_RCU_TRACE */
> > --
> > 1.8.1.5
> >
> --
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