# Re: \[PATCH v10 04/14\] unwind\_user/deferred: Add unwind\_deferred\_trace()

- From: Peter Zijlstra \<peterz@infradead.org\>
- Date: 2025-06-18 14:01:18 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2025/06/3097478
- Thread: https://ratatoskr.run/linux-trace-kernel/2025/06/3086227/t.md

```text
On Tue, Jun 10, 2025 at 08:54:25PM -0400, Steven Rostedt wrote:

> +#define UNWIND_MAX_ENTRIES 512

The reason this is 512 is so that you end up with a whole page below?

> +int unwind_deferred_trace(struct unwind_stacktrace *trace)
> +{
> +	struct unwind_task_info *info = &current->unwind_info;
> +
> +	/* Should always be called from faultable context */
> +	might_fault();
> +
> +	if (current->flags & PF_EXITING)
> +		return -EINVAL;
> +
> +	if (!info->entries) {
> +		info->entries = kmalloc_array(UNWIND_MAX_ENTRIES, sizeof(long),
> +					      GFP_KERNEL);


```