On Thu, 18 Oct 2012, Kamezawa Hiroyuki wrote:
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 14df880..d92e868 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -94,6 +94,11 @@ static void vma_stop(struct proc_maps_private *priv, struct
> vm_area_struct *vma)
> {
> if (vma && vma != priv->tail_vma) {
> struct mm_struct *mm = vma->vm_mm;
> +#ifdef CONFIG_NUMA
> + task_lock(priv->task);
> + __mpol_put(priv->task->mempolicy);
> + task_unlock(priv->task);
> +#endif
> up_read(&mm->mmap_sem);
> mmput(mm);
> }
> @@ -130,6 +135,16 @@ static void *m_start(struct seq_file *m, loff_t *pos)
> return mm;
> down_read(&mm->mmap_sem);
> + /*
> + * task->mempolicy can be freed even if mmap_sem is down (see
> kernel/exit.c)
> + * We grab refcount for stable access.
> + * repleacement of task->mmpolicy is guarded by mmap_sem.
> + */
> +#ifdef CONFIG_NUMA
> + task_lock(priv->task);
> + mpol_get(priv->task->mempolicy);
> + task_unlock(priv->task);
> +#endif
> tail_vma = get_gate_vma(priv->task->mm);
> priv->tail_vma = tail_vma;
> @@ -161,6 +176,11 @@ out:
> /* End of vmas has been reached */
> m->version = (tail_vma != NULL)? 0: -1UL;
> +#ifdef CONFIG_NUMA
> + task_lock(priv->task);
> + __mpol_put(priv->task->mempolicy);
> + task_unlock(priv->task);
> +#endif
> up_read(&mm->mmap_sem);
> mmput(mm);
> return tail_vma;
Yes, I must admit that this is better than my version and it looks like
all the ->show() functions that use these start, next, stop functions
don't take task_lock() and this would generally be useful: we already hold
current->mm->mmap_sem so there is little harm in holding
task_lock(current) when reading these files as long as we're not touching
the fastpath.
These routines seem like it would nicely be added to mempolicy.h since we
depend on CONFIG_NUMA there already.
Please fix up the mess I made in show_numa_map() in 32f8516a8c73 ("mm,
mempolicy: fix printing stack contents in numa_maps") by simply removing
the task_lock() and task_unlock() as part of your patch.
Thanks Kame!
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