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SubjectRe: [PATCH v7 3.2-rc2 3/30] uprobes: register/unregister probes.
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On Fri, 2011-11-18 at 16:37 +0530, Srikar Dronamraju wrote:
> +static void __unregister_uprobe(struct inode *inode, loff_t offset,
> + struct uprobe *uprobe)
> +{
> + struct list_head try_list;
> + struct address_space *mapping;
> + struct vma_info *vi, *tmpvi;
> + struct vm_area_struct *vma;
> + struct mm_struct *mm;
> + loff_t vaddr;
> +
> + mapping = inode->i_mapping;
> + INIT_LIST_HEAD(&try_list);
> + while ((vi = find_next_vma_info(&try_list, offset,
> + mapping, false)) != NULL) {
> + if (IS_ERR(vi))
> + break;

So what kind of half-assed state are we left in if we try an unregister
under memory pressure and how do we deal with that?

> + mm = vi->mm;
> + down_read(&mm->mmap_sem);
> + vma = find_vma(mm, (unsigned long)vi->vaddr);
> + if (!vma || !valid_vma(vma, false)) {
> + list_del(&vi->probe_list);
> + kfree(vi);
> + up_read(&mm->mmap_sem);
> + mmput(mm);
> + continue;
> + }
> + vaddr = vma->vm_start + offset;
> + vaddr -= vma->vm_pgoff << PAGE_SHIFT;
> + if (vma->vm_file->f_mapping->host != inode ||
> + vaddr != vi->vaddr) {
> + list_del(&vi->probe_list);
> + kfree(vi);
> + up_read(&mm->mmap_sem);
> + mmput(mm);
> + continue;
> + }
> + remove_breakpoint(mm);
> + up_read(&mm->mmap_sem);
> + mmput(mm);
> + }
> +
> + list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
> + list_del(&vi->probe_list);
> + kfree(vi);
> + }
> + delete_uprobe(uprobe);
> +}


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