On Thu, Apr 24, 2025 at 12:25:41PM -0400, Steven Rostedt wrote:
> From: Josh Poimboeuf <[email protected]>
>
> If the task doesn't have any memory, there's no stack to unwind.
>
> Signed-off-by: Josh Poimboeuf <[email protected]>
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
> ---
> Note from v4:
> https://lore.kernel.org/all/24cde1381495cd637f0d5663ab7629572bc0eca6.1737511963.git.jpoim...@kernel.org/
>
> - From the previous version, Peter Zijlstra brought up concern about
> io_uring helpers, but this was never resolved. No update was made.
What is there to resolve? If you want to check for kthreads, don't check
for ->mm
>
> kernel/events/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 009f34bd9e63..40b98b05fb7c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8101,7 +8101,7 @@ struct perf_callchain_entry *
> perf_callchain(struct perf_event *event, struct pt_regs *regs)
> {
> bool kernel = !event->attr.exclude_callchain_kernel;
> - bool user = !event->attr.exclude_callchain_user;
> + bool user = !event->attr.exclude_callchain_user && current->mm;
> /* Disallow cross-task user callchains. */
> bool crosstask = event->ctx->task && event->ctx->task != current;
> const u32 max_stack = event->attr.sample_max_stack;
> --
> 2.47.2
>
>
