Thank Paul for your encouragement and valuable advice
I achieve great self improvement in studying and participating Linux RCU
Also thank Neeraj for mutual interest in Linux RCU, your contribution
makes me believe
that even a small enhancement of code can still attract interest and
draw favorable attention
from peers.
Cheers
Zhouyi
On Wed, Jan 13, 2021 at 1:50 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
> Good catch, applied, thank you! As usual, I edited a bit, so please
> check below to see if I messed anything up.
>
> I did add Neeraj Upadhyay's Reported-by because he noted this, though you
> beat him with a public posting, though mostly because I asked him whether
> he could make this happen. I also added the Fixes, but could you please
> do that in the future? You can use "git blame" or either "git log" and
> "gitk" with appropriate options to find the offending commit.
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 3f91ff7fd4f76e7eb48bad79666c466bc3530324
> Author: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
> Date: Mon Jan 11 09:08:59 2021 +0800
>
> rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()
>
> In rcu_nmi_enter(), there is an erroneous instrumentation_end() in the
> second branch of the "if" statement. Oddly enough, "objtool check -f
> vmlinux.o" fails to complain because it is unable to correctly cover
> all cases. Instead, objtool visits the third branch first, which marks
> following trace_rcu_dyntick() as visited. This commit therefore removes
> the spurious instrumentation_end().
>
> Fixes: 04b25a495bd6 ("rcu: Mark rcu_nmi_enter() call to rcu_cleanup_after_idle() noinstr")
> Reported-by Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
> Signed-off-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 63c6dba..e04e336 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1050,7 +1050,6 @@ noinstr void rcu_nmi_enter(void)
> } else if (!in_nmi()) {
> instrumentation_begin();
> rcu_irq_enter_check_tick();
> - instrumentation_end();
> } else {
> instrumentation_begin();
> }
