Messages in this thread | | | Date | Tue, 19 Sep 2017 10:57:28 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/2] smp/hotplug,lockdep: Annotate cpuhp_state |
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On Tue, Sep 05, 2017 at 09:52:20AM +0200, Peter Zijlstra wrote: > After the st->done annotation, lockdep cross-release now complains > about: > > CPU0 CPU1 CPU2 > cpuhp_up_callbacks: takedown_cpu: cpuhp_thread_fun: > > cpuhp_state > irq_lock_sparse() > irq_lock_sparse() > wait_for_completion() > cpuhp_state > complete() > > which again spells deadlock, because CPU0 needs to wait for CPU1's > irq_lock_sparse which will wait for CPU2's completion, which in turn > waits for CPU0's cpuhp_state. > > Now, this again mixes up and down chains, but now on cpuhp_state. > > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Byungchul Park <max.byungchul.park@gmail.com> > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > Reported-by: Mike Galbraith <efault@gmx.de> > Tested-by: Mike Galbraith <efault@gmx.de> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > kernel/cpu.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -67,11 +67,14 @@ struct cpuhp_cpu_state { > static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state); > > #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP) > -static struct lock_class_key cpuhp_state_key; > +static struct lock_class_key cpuhp_state_up_key; > +#ifdef CONFIG_HOTPLUG_CPU > +static struct lock_class_key cpuhp_state_down_key; > +#endif
These two patches work for me if CONFIG_PROVE_LOCKING=y, but the lockdep_init_map() wants its key argument to exist if CONFIG_PROVE_LOCKING=n.
Not sure whether it is better to remove the CONFIG_LOCKDEP #if on the one hand or to make lockdep_init_map() lose the "(void)" things on the other...
My tests didn't involve failing CPU hotplug operations, so I didn't run into the issue Thomas was concerned about.
Thanx, Paul
> static struct lockdep_map cpuhp_state_lock_map = > - STATIC_LOCKDEP_MAP_INIT("cpuhp_state", &cpuhp_state_key); > + STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_key); > #endif > > /** > * cpuhp_step - Hotplug state machine step > * @name: Name of the step > @@ -714,6 +718,8 @@ static int __ref _cpu_down(unsigned int > cpus_write_lock(); > > lockdep_reinit_st_done(); > + lockdep_init_map(&cpuhp_state_lock_map, "cpuhp_state-down", > + &cpuhp_state_down_key, 0); > > cpuhp_tasks_frozen = tasks_frozen; > > @@ -828,6 +834,8 @@ static int _cpu_up(unsigned int cpu, int > cpus_write_lock(); > > lockdep_reinit_st_done(); > + lockdep_init_map(&cpuhp_state_lock_map, "cpuhp_state-up", > + &cpuhp_state_up_key, 0); > > if (!cpu_present(cpu)) { > ret = -EINVAL; > >
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