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SubjectRe: [RFC] [PATCH 2.6.37-rc5-tip 8/20] 8: uprobes: mmap and fork hooks.
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On Thu, 2010-12-16 at 15:28 +0530, Srikar Dronamraju wrote:
> +void uprobe_mmap(struct vm_area_struct *vma)
> +{
> + struct list_head tmp_list;
> + struct uprobe *uprobe, *u;
> + struct mm_struct *mm;
> + struct inode *inode;
> +
> + if (!valid_vma(vma))
> + return;
> +
> + INIT_LIST_HEAD(&tmp_list);
> +
> + /*
> + * The vma was just allocated and this routine gets called
> + * while holding write lock for mmap_sem. Function called
> + * in context of a thread that has a reference to mm.
> + * Hence no need to take a reference to mm
> + */
> + mm = vma->vm_mm;
> + up_write(&mm->mmap_sem);

Are you very very sure its a good thing to simply drop the mmap_sem
here? Also, why?

> + mutex_lock(&uprobes_mutex);
> +
> + inode = vma->vm_file->f_mapping->host;

Since you just dropped the mmap_sem, what's keeping that vma from going
away?

> + add_to_temp_list(vma, inode, &tmp_list);
> +
> + list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
> + mm->uprobes_vaddr = vma->vm_start + uprobe->offset;
> + install_uprobe(mm, uprobe);
> + list_del(&uprobe->pending_list);
> + }
> + mutex_unlock(&uprobes_mutex);
> + down_write(&mm->mmap_sem);
> +}




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