| Message ID | 20221122010421.3799681-5-paulmck@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 3d222a0c0cfef85bad2c9cff5d541836cb81cfbd |
| Headers | show |
| Series | [v2,01/16] rcu: Simplify rcu_init_nohz() cpumask handling | expand |
On Mon, Nov 21, 2022 at 05:04:10PM -0800, Paul E. McKenney wrote: > From: "Joel Fernandes (Google)" <joel@joelfernandes.org> > > This consolidates the code a bit and makes it cleaner. Functionally it > is the same. > > Reported-by: Paul E. McKenney <paulmck@kernel.org> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > --- > 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? > > 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@kernel.org> Thanks. > > rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl); > WRITE_ONCE(rdp->nocb_bypass_first, j); > -- > 2.31.1.189.g2e36527f23 >
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@joelfernandes.org> > > > > This consolidates the code a bit and makes it cleaner. Functionally it > > is the same. > > > > Reported-by: Paul E. McKenney <paulmck@kernel.org> > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > --- > > 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. > > 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@kernel.org> 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 > >
> On Nov 23, 2022, at 12:54 PM, Paul E. McKenney <paulmck@kernel.org> 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@joelfernandes.org> >>> >>> This consolidates the code a bit and makes it cleaner. Functionally it >>> is the same. >>> >>> Reported-by: Paul E. McKenney <paulmck@kernel.org> >>> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> >>> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> >>> --- >>> 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@kernel.org> > > 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 >>>
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; 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); rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl); WRITE_ONCE(rdp->nocb_bypass_first, j);