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SubjectRe: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes.
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On Thu, 2010-12-16 at 15:28 +0530, Srikar Dronamraju wrote:
> +void unregister_uprobe(struct inode *inode, unsigned long offset,
> + struct uprobe_consumer *consumer)
> +{
> + struct prio_tree_iter iter;
> + struct list_head tmp_list;
> + struct address_space *mapping;
> + struct mm_struct *mm, *tmpmm;
> + struct vm_area_struct *vma;
> + struct uprobe *uprobe;
> +
> + if (!inode || !consumer)
> + return;
> +
> + uprobe = find_uprobe(inode, offset);
> + if (!uprobe) {
> + printk(KERN_ERR "No uprobe found with inode:offset %p %lu\n",
> + inode, offset);
> + return;
> + }
> +
> + if (!del_consumer(uprobe, consumer)) {
> + printk(KERN_ERR "No uprobe found with consumer %p\n",
> + consumer);
> + return;
> + }
> +
> + INIT_LIST_HEAD(&tmp_list);
> +
> + mapping = inode->i_mapping;
> +
> + mutex_lock(&uprobes_mutex);
> + if (uprobe->consumers)
> + goto put_unlock;
> +
> + spin_lock(&mapping->i_mmap_lock);
> + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, 0) {
> + if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
> + continue;
> +
> + mm = vma->vm_mm;
> +
> + if (!atomic_read(&mm->uprobes_count)) {
> + mmput(mm);
> + continue;
> + }
> +
> + if (valid_vma(vma)) {
> + list_add(&mm->uprobes_list, &tmp_list);
> + mm->uprobes_vaddr = vma->vm_start + offset;
> + } else
> + mmput(mm);
> + }
> + spin_unlock(&mapping->i_mmap_lock);
> + list_for_each_entry_safe(mm, tmpmm, &tmp_list, uprobes_list) {
> + remove_uprobe(mm, uprobe);
> + list_del(&mm->uprobes_list);
> + mmput(mm);
> + }
> +
> + if (atomic_read(&uprobe->ref) == 1) {
> + synchronize_sched();
> + rb_erase(&uprobe->rb_node, &uprobes_tree);

How is that safe without holding the treelock?

> + iput(uprobe->inode);
> + }
> +
> +put_unlock:
> + mutex_unlock(&uprobes_mutex);
> + put_uprobe(uprobe);
> +}


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