Re: [PATCH v10 04/14] unwind_user/deferred: Add unwind_deferred_trace()
From: Peter Zijlstra
Date: Wed Jun 18 2025 - 10:03:56 EST
On Tue, Jun 10, 2025 at 08:54:25PM -0400, Steven Rostedt wrote:
> +/**
> + * unwind_deferred_trace - Produce a user stacktrace in faultable context
> + * @trace: The descriptor that will store the user stacktrace
> + *
> + * This must be called in a known faultable context (usually when entering
> + * or exiting user space). Depending on the available implementations
> + * the @trace will be loaded with the addresses of the user space stacktrace
> + * if it can be found.
I am confused -- why would we ever want to call this on exiting
user-space, or rather kernel entry?
I thought the whole point was to request a user trace while in-kernel,
and defer that to return-to-user.