Re: [PATCH 5/8] trace_uprobe: Support SDT markers having reference count (semaphore)

[Steven Rostedt]

On Tue, 13 Mar 2018 18:26:00 +0530
Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx> wrote:

> +static void sdt_increment_ref_ctr(struct trace_uprobe *tu)
> +{
> +	struct uprobe_map_info *info;
> +	struct vm_area_struct *vma;
> +	unsigned long vaddr;
> +
> +	uprobe_start_dup_mmap();

Please add a comment here that this function ups the mm ref count for
each info returned. Otherwise it's hard to know what that mmput() below
matches.

-- Steve

> +	info = uprobe_build_map_info(tu->inode->i_mapping,
> +				tu->ref_ctr_offset, false);
> +	if (IS_ERR(info))
> +		goto out;
> +
> +	while (info) {
> +		down_write(&info->mm->mmap_sem);
> +
> +		vma = sdt_find_vma(info->mm, tu);
> +		vaddr = vma_offset_to_vaddr(vma, tu->ref_ctr_offset);
> +		sdt_update_ref_ctr(info->mm, vaddr, 1);
> +
> +		up_write(&info->mm->mmap_sem);
> +		mmput(info->mm);
> +		info = uprobe_free_map_info(info);
> +	}
> +
> +out:
> +	uprobe_end_dup_mmap();
> +}
> +