On Fri, Nov 13, 2020 at 01:13:32PM +0100, Frederic Weisbecker wrote: > RCU needs to check if the cpu hotplug lock is held, in the middle of > other conditions to check the sanity of RCU-nocb. Provide a helper for > that. > > Signed-off-by: Frederic Weisbecker <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Josh Triplett <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Mathieu Desnoyers <[email protected]> > Cc: Lai Jiangshan <[email protected]> > Cc: Joel Fernandes <[email protected]> > Cc: Neeraj Upadhyay <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Boqun Feng <[email protected]> > --- > include/linux/cpu.h | 1 + > kernel/cpu.c | 7 +++++++ > 2 files changed, 8 insertions(+) > > diff --git a/include/linux/cpu.h b/include/linux/cpu.h > index d6428aaf67e7..27eb3875e45a 100644 > --- a/include/linux/cpu.h > +++ b/include/linux/cpu.h > @@ -118,6 +118,7 @@ extern void cpus_read_lock(void); > extern void cpus_read_unlock(void); > extern int cpus_read_trylock(void); > extern void lockdep_assert_cpus_held(void); > +extern int lockdep_is_cpus_held(void); > extern void cpu_hotplug_disable(void); > extern void cpu_hotplug_enable(void); > void clear_tasks_mm_cpumask(int cpu); > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 6ff2578ecf17..3cca5b27de25 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -330,6 +330,13 @@ void lockdep_assert_cpus_held(void) > percpu_rwsem_assert_held(&cpu_hotplug_lock); > } > > +#ifdef CONFIG_LOCKDEP > +int lockdep_is_cpus_held(void) > +{ > + return percpu_rwsem_is_held(&cpu_hotplug_lock); > +} > +#endif > + > static void lockdep_acquire_cpus_lock(void) > { > rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
This patch may trigger a build error with !CONFIG_HOTPLUG. Here is a fixed version: --- >From 80609608b29758e43e8d8d6beaca486b8c42bb43 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker <[email protected]> Date: Wed, 11 Nov 2020 23:53:13 +0100 Subject: [PATCH] cpu/hotplug: Add lockdep_is_cpus_held() RCU needs to check if the cpu hotplug lock is held, in the middle of other conditions to check the sanity of RCU-nocb. Provide a helper for that. Signed-off-by: Frederic Weisbecker <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Josh Triplett <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Lai Jiangshan <[email protected]> Cc: Joel Fernandes <[email protected]> Cc: Neeraj Upadhyay <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Boqun Feng <[email protected]> --- include/linux/cpu.h | 2 ++ kernel/cpu.c | 7 +++++++ 2 files changed, 9 insertions(+) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index d6428aaf67e7..3aaa0687e8df 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -111,6 +111,8 @@ static inline void cpu_maps_update_done(void) #endif /* CONFIG_SMP */ extern struct bus_type cpu_subsys; +extern int lockdep_is_cpus_held(void); + #ifdef CONFIG_HOTPLUG_CPU extern void cpus_write_lock(void); extern void cpus_write_unlock(void); diff --git a/kernel/cpu.c b/kernel/cpu.c index 6ff2578ecf17..3cca5b27de25 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -330,6 +330,13 @@ void lockdep_assert_cpus_held(void) percpu_rwsem_assert_held(&cpu_hotplug_lock); } +#ifdef CONFIG_LOCKDEP +int lockdep_is_cpus_held(void) +{ + return percpu_rwsem_is_held(&cpu_hotplug_lock); +} +#endif + static void lockdep_acquire_cpus_lock(void) { rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_); -- 2.25.1
