Messages in this thread | | | Date | Wed, 4 Sep 2019 12:53:49 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC PATCH 1/2] Fix: sched/membarrier: p->mm->membarrier_state racy load |
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On 09/03, Mathieu Desnoyers wrote: > > @@ -1130,6 +1130,10 @@ struct task_struct { > unsigned long numa_pages_migrated; > #endif /* CONFIG_NUMA_BALANCING */ > > +#ifdef CONFIG_MEMBARRIER > + atomic_t membarrier_state; > +#endif
...
> +static inline void membarrier_prepare_task_switch(struct task_struct *t) > +{ > + if (!t->mm) > + return; > + atomic_set(&t->membarrier_state, > + atomic_read(&t->mm->membarrier_state)); > +}
Why not
rq->membarrier_state = next->mm ? t->mm->membarrier_state : 0;
and
if (cpu_rq(cpu)->membarrier_state & MEMBARRIER_STATE_GLOBAL_EXPEDITED) { ... }
in membarrier_global_expedited() ? (I removed atomic_ to simplify)
IOW, why this new member has to live in task_struct, not in rq?
Oleg.
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