| Message ID | 20230908203603.5865-8-frederic@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 2cb1f6e9a743af58a23cf14563b5eada1e0d3fde |
| Headers | show |
| Series | rcu cleanups | expand |
On Fri, Sep 08, 2023 at 10:36:00PM +0200, Frederic Weisbecker wrote: > Among the three CPU-hotplug teardown RCU callbacks, two of them early > exit if CONFIG_HOTPLUG_CPU=n, and one is left unchanged. In any case > all of them have an implementation when CONFIG_HOTPLUG_CPU=n. > > Align instead with the common way to deal with CPU-hotplug teardown > callbacks and provide a proper stub when they are not supported. > > Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Good eyes! Reviewed-by: Paul E. McKenney <paulmck@kernel.org> > --- > include/linux/rcutree.h | 11 +++- > kernel/rcu/tree.c | 114 +++++++++++++++++++--------------------- > 2 files changed, 63 insertions(+), 62 deletions(-) > > diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h > index af6ddbd291eb..7d75066c72aa 100644 > --- a/include/linux/rcutree.h > +++ b/include/linux/rcutree.h > @@ -109,9 +109,16 @@ void rcu_all_qs(void); > /* RCUtree hotplug events */ > int rcutree_prepare_cpu(unsigned int cpu); > int rcutree_online_cpu(unsigned int cpu); > -int rcutree_offline_cpu(unsigned int cpu); > +void rcu_cpu_starting(unsigned int cpu); > + > +#ifdef CONFIG_HOTPLUG_CPU > int rcutree_dead_cpu(unsigned int cpu); > int rcutree_dying_cpu(unsigned int cpu); > -void rcu_cpu_starting(unsigned int cpu); > +int rcutree_offline_cpu(unsigned int cpu); > +#else > +#define rcutree_dead_cpu NULL > +#define rcutree_dying_cpu NULL > +#define rcutree_offline_cpu NULL > +#endif > > #endif /* __LINUX_RCUTREE_H */ > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 289c51417cbc..875f241db508 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -4228,25 +4228,6 @@ static bool rcu_init_invoked(void) > return !!rcu_state.n_online_cpus; > } > > -/* > - * Near the end of the offline process. Trace the fact that this CPU > - * is going offline. > - */ > -int rcutree_dying_cpu(unsigned int cpu) > -{ > - bool blkd; > - struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); > - struct rcu_node *rnp = rdp->mynode; > - > - if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) > - return 0; > - > - blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask); > - trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), > - blkd ? TPS("cpuofl-bgp") : TPS("cpuofl")); > - return 0; > -} > - > /* > * All CPUs for the specified rcu_node structure have gone offline, > * and all tasks that were preempted within an RCU read-side critical > @@ -4292,23 +4273,6 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) > } > } > > -/* > - * The CPU has been completely removed, and some other CPU is reporting > - * this fact from process context. Do the remainder of the cleanup. > - * There can only be one CPU hotplug operation at a time, so no need for > - * explicit locking. > - */ > -int rcutree_dead_cpu(unsigned int cpu) > -{ > - if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) > - return 0; > - > - WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); > - // Stop-machine done, so allow nohz_full to disable tick. > - tick_dep_clear(TICK_DEP_BIT_RCU); > - return 0; > -} > - > /* > * Propagate ->qsinitmask bits up the rcu_node tree to account for the > * first CPU in a given leaf rcu_node structure coming online. The caller > @@ -4461,29 +4425,6 @@ int rcutree_online_cpu(unsigned int cpu) > return 0; > } > > -/* > - * Near the beginning of the process. The CPU is still very much alive > - * with pretty much all services enabled. > - */ > -int rcutree_offline_cpu(unsigned int cpu) > -{ > - unsigned long flags; > - struct rcu_data *rdp; > - struct rcu_node *rnp; > - > - rdp = per_cpu_ptr(&rcu_data, cpu); > - rnp = rdp->mynode; > - raw_spin_lock_irqsave_rcu_node(rnp, flags); > - rnp->ffmask &= ~rdp->grpmask; > - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > - > - rcutree_affinity_setting(cpu, cpu); > - > - // nohz_full CPUs need the tick for stop-machine to work quickly > - tick_dep_set(TICK_DEP_BIT_RCU); > - return 0; > -} > - > /* > * Mark the specified CPU as being online so that subsequent grace periods > * (both expedited and normal) will wait on it. Note that this means that > @@ -4637,7 +4578,60 @@ void rcutree_migrate_callbacks(int cpu) > cpu, rcu_segcblist_n_cbs(&rdp->cblist), > rcu_segcblist_first_cb(&rdp->cblist)); > } > -#endif > + > +/* > + * The CPU has been completely removed, and some other CPU is reporting > + * this fact from process context. Do the remainder of the cleanup. > + * There can only be one CPU hotplug operation at a time, so no need for > + * explicit locking. > + */ > +int rcutree_dead_cpu(unsigned int cpu) > +{ > + WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); > + // Stop-machine done, so allow nohz_full to disable tick. > + tick_dep_clear(TICK_DEP_BIT_RCU); > + return 0; > +} > + > +/* > + * Near the end of the offline process. Trace the fact that this CPU > + * is going offline. > + */ > +int rcutree_dying_cpu(unsigned int cpu) > +{ > + bool blkd; > + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); > + struct rcu_node *rnp = rdp->mynode; > + > + blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask); > + trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), > + blkd ? TPS("cpuofl-bgp") : TPS("cpuofl")); > + return 0; > +} > + > +/* > + * Near the beginning of the process. The CPU is still very much alive > + * with pretty much all services enabled. > + */ > +int rcutree_offline_cpu(unsigned int cpu) > +{ > + unsigned long flags; > + struct rcu_data *rdp; > + struct rcu_node *rnp; > + > + rdp = per_cpu_ptr(&rcu_data, cpu); > + rnp = rdp->mynode; > + raw_spin_lock_irqsave_rcu_node(rnp, flags); > + rnp->ffmask &= ~rdp->grpmask; > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > + > + rcutree_affinity_setting(cpu, cpu); > + > + // nohz_full CPUs need the tick for stop-machine to work quickly > + tick_dep_set(TICK_DEP_BIT_RCU); > + return 0; > +} > +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ > > /* > * On non-huge systems, use expedited RCU grace periods to make suspend > -- > 2.41.0 >
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index af6ddbd291eb..7d75066c72aa 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -109,9 +109,16 @@ void rcu_all_qs(void); /* RCUtree hotplug events */ int rcutree_prepare_cpu(unsigned int cpu); int rcutree_online_cpu(unsigned int cpu); -int rcutree_offline_cpu(unsigned int cpu); +void rcu_cpu_starting(unsigned int cpu); + +#ifdef CONFIG_HOTPLUG_CPU int rcutree_dead_cpu(unsigned int cpu); int rcutree_dying_cpu(unsigned int cpu); -void rcu_cpu_starting(unsigned int cpu); +int rcutree_offline_cpu(unsigned int cpu); +#else +#define rcutree_dead_cpu NULL +#define rcutree_dying_cpu NULL +#define rcutree_offline_cpu NULL +#endif #endif /* __LINUX_RCUTREE_H */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 289c51417cbc..875f241db508 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4228,25 +4228,6 @@ static bool rcu_init_invoked(void) return !!rcu_state.n_online_cpus; } -/* - * Near the end of the offline process. Trace the fact that this CPU - * is going offline. - */ -int rcutree_dying_cpu(unsigned int cpu) -{ - bool blkd; - struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); - struct rcu_node *rnp = rdp->mynode; - - if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) - return 0; - - blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask); - trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), - blkd ? TPS("cpuofl-bgp") : TPS("cpuofl")); - return 0; -} - /* * All CPUs for the specified rcu_node structure have gone offline, * and all tasks that were preempted within an RCU read-side critical @@ -4292,23 +4273,6 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) } } -/* - * The CPU has been completely removed, and some other CPU is reporting - * this fact from process context. Do the remainder of the cleanup. - * There can only be one CPU hotplug operation at a time, so no need for - * explicit locking. - */ -int rcutree_dead_cpu(unsigned int cpu) -{ - if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) - return 0; - - WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); - // Stop-machine done, so allow nohz_full to disable tick. - tick_dep_clear(TICK_DEP_BIT_RCU); - return 0; -} - /* * Propagate ->qsinitmask bits up the rcu_node tree to account for the * first CPU in a given leaf rcu_node structure coming online. The caller @@ -4461,29 +4425,6 @@ int rcutree_online_cpu(unsigned int cpu) return 0; } -/* - * Near the beginning of the process. The CPU is still very much alive - * with pretty much all services enabled. - */ -int rcutree_offline_cpu(unsigned int cpu) -{ - unsigned long flags; - struct rcu_data *rdp; - struct rcu_node *rnp; - - rdp = per_cpu_ptr(&rcu_data, cpu); - rnp = rdp->mynode; - raw_spin_lock_irqsave_rcu_node(rnp, flags); - rnp->ffmask &= ~rdp->grpmask; - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - - rcutree_affinity_setting(cpu, cpu); - - // nohz_full CPUs need the tick for stop-machine to work quickly - tick_dep_set(TICK_DEP_BIT_RCU); - return 0; -} - /* * Mark the specified CPU as being online so that subsequent grace periods * (both expedited and normal) will wait on it. Note that this means that @@ -4637,7 +4578,60 @@ void rcutree_migrate_callbacks(int cpu) cpu, rcu_segcblist_n_cbs(&rdp->cblist), rcu_segcblist_first_cb(&rdp->cblist)); } -#endif + +/* + * The CPU has been completely removed, and some other CPU is reporting + * this fact from process context. Do the remainder of the cleanup. + * There can only be one CPU hotplug operation at a time, so no need for + * explicit locking. + */ +int rcutree_dead_cpu(unsigned int cpu) +{ + WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); + // Stop-machine done, so allow nohz_full to disable tick. + tick_dep_clear(TICK_DEP_BIT_RCU); + return 0; +} + +/* + * Near the end of the offline process. Trace the fact that this CPU + * is going offline. + */ +int rcutree_dying_cpu(unsigned int cpu) +{ + bool blkd; + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + struct rcu_node *rnp = rdp->mynode; + + blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask); + trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), + blkd ? TPS("cpuofl-bgp") : TPS("cpuofl")); + return 0; +} + +/* + * Near the beginning of the process. The CPU is still very much alive + * with pretty much all services enabled. + */ +int rcutree_offline_cpu(unsigned int cpu) +{ + unsigned long flags; + struct rcu_data *rdp; + struct rcu_node *rnp; + + rdp = per_cpu_ptr(&rcu_data, cpu); + rnp = rdp->mynode; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + rnp->ffmask &= ~rdp->grpmask; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + + rcutree_affinity_setting(cpu, cpu); + + // nohz_full CPUs need the tick for stop-machine to work quickly + tick_dep_set(TICK_DEP_BIT_RCU); + return 0; +} +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ /* * On non-huge systems, use expedited RCU grace periods to make suspend
Among the three CPU-hotplug teardown RCU callbacks, two of them early exit if CONFIG_HOTPLUG_CPU=n, and one is left unchanged. In any case all of them have an implementation when CONFIG_HOTPLUG_CPU=n. Align instead with the common way to deal with CPU-hotplug teardown callbacks and provide a proper stub when they are not supported. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> --- include/linux/rcutree.h | 11 +++- kernel/rcu/tree.c | 114 +++++++++++++++++++--------------------- 2 files changed, 63 insertions(+), 62 deletions(-)