> On Nov 23, 2022, at 12:54 PM, Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> On Wed, Nov 23, 2022 at 04:59:29PM +0100, Frederic Weisbecker wrote:
>>> On Mon, Nov 21, 2022 at 05:04:10PM -0800, Paul E. McKenney wrote:
>>> From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>
>>>
>>> This consolidates the code a bit and makes it cleaner. Functionally it
>>> is the same.
>>>
>>> Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>>> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
>>> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>>> ---
>>> kernel/rcu/tree_nocb.h | 17 +++++++++--------
>>> 1 file changed, 9 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
>>> index d6e4c076b0515..213daf81c057f 100644
>>> --- a/kernel/rcu/tree_nocb.h
>>> +++ b/kernel/rcu/tree_nocb.h
>>> @@ -327,10 +327,11 @@ static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
>>> *
>>> * Note that this function always returns true if rhp is NULL.
>>> */
>>> -static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
>>> +static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp_in,
>>> unsigned long j, bool lazy)
>>> {
>>> struct rcu_cblist rcl;
>>> + struct rcu_head *rhp = rhp_in;
>>
>> Why that intermediate rhp_in?
>
> To avoid modifying the formal parameter, should the original value prove
> useful, for example, for tracing or debugging.
So as to not re assign function parameter and introduce bugs down the line (someone reading code thinks they passed a certain rhp but code is using something else later in the function).
Thanks.
>
>>> WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp));
>>> rcu_lockdep_assert_cblist_protected(rdp);
>>> @@ -345,16 +346,16 @@ static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
>>>
>>> /*
>>> * If the new CB requested was a lazy one, queue it onto the main
>>> - * ->cblist so we can take advantage of a sooner grade period.
>>> + * ->cblist so that we can take advantage of the grace-period that will
>>> + * happen regardless. But queue it onto the bypass list first so that
>>> + * the lazy CB is ordered with the existing CBs in the bypass list.
>>> */
>>> if (lazy && rhp) {
>>> - rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, NULL);
>>> - rcu_cblist_enqueue(&rcl, rhp);
>>> - WRITE_ONCE(rdp->lazy_len, 0);
>>> - } else {
>>> - rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
>>> - WRITE_ONCE(rdp->lazy_len, 0);
>>> + rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
>>> + rhp = NULL;
>>> }
>>> + rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
>>> + WRITE_ONCE(rdp->lazy_len, 0);
>>
>> Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
>
> Thank you! I will apply this on my next rebase.
>
> Thanx, Paul
>
>> Thanks.
>>
>>>
>>> rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
>>> WRITE_ONCE(rdp->nocb_bypass_first, j);
>>> --
>>> 2.31.1.189.g2e36527f23
>>>
