On Tue, Sep 19, 2017 at 06:13:41PM -0400, Mathieu Desnoyers wrote:
[...]
> +static inline void membarrier_arch_sched_in(struct task_struct *prev,
> + struct task_struct *next)
> +{
> + /*
> + * Only need the full barrier when switching between processes.
> + */
> + if (likely(!test_ti_thread_flag(task_thread_info(next),
> + TIF_MEMBARRIER_PRIVATE_EXPEDITED)
> + || prev->mm == next->mm))
And we also don't need the smp_mb() if !prev->mm, because switching from
kernel to user will have a smp_mb() implied by mmdrop()?
> + return;
> +
> + /*
> + * The membarrier system call requires a full memory barrier
> + * after storing to rq->curr, before going back to user-space.
> + */
> + smp_mb();
> +}
[...]
> +static inline void membarrier_fork(struct task_struct *t,
> + unsigned long clone_flags)
> +{
> + if (!current->mm || !t->mm)
> + return;
> + t->mm->membarrier_private_expedited =
> + current->mm->membarrier_private_expedited;
Have we already done the copy of ->membarrier_private_expedited in
copy_mm()?
Regards,
Boqun
> + membarrier_arch_fork(t, clone_flags);
> +}
> +static inline void membarrier_execve(struct task_struct *t)
> +{
> + t->mm->membarrier_private_expedited = 0;
> + membarrier_arch_execve(t);
> +}
> +#else
> +static inline void membarrier_sched_in(struct task_struct *prev,
> + struct task_struct *next)
> +{
> +}
> +static inline void membarrier_fork(struct task_struct *t,
> + unsigned long clone_flags)
> +{
> +}
> +static inline void membarrier_execve(struct task_struct *t)
> +{
> +}
> +#endif
> +
[...]
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