On Thu, Apr 24, 2025 at 12:25:40PM -0400, Steven Rostedt wrote:
> From: Josh Poimboeuf <[email protected]>
>
> Simplify the get_perf_callchain() user logic a bit. task_pt_regs()
> should never be NULL.
>
> Acked-by: Namhyung Kim <[email protected]>
> Signed-off-by: Josh Poimboeuf <[email protected]>
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
> ---
> kernel/events/callchain.c | 20 +++++++++-----------
> 1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
> index abf258913ab6..bba7f8540ade 100644
> --- a/kernel/events/callchain.c
> +++ b/kernel/events/callchain.c
> @@ -246,22 +246,20 @@ get_perf_callchain(struct pt_regs *regs, bool kernel,
> bool user,
>
> if (user) {
> if (!user_mode(regs)) {
> - if (current->mm)
> - regs = task_pt_regs(current);
> - else
> - regs = NULL;
> + if (!current->mm)
> + goto exit_put;
> + regs = task_pt_regs(current);
I'm thinking this might be one of those is-kthread test written as
has-mm, and they're broken.
Notably things like the io-uring kthreads do have mm.
> }
>
> - if (regs) {
> - if (add_mark)
> - perf_callchain_store_context(&ctx,
> PERF_CONTEXT_USER);
> + if (add_mark)
> + perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
>
> - start_entry_idx = entry->nr;
> - perf_callchain_user(&ctx, regs);
> - fixup_uretprobe_trampoline_entries(entry,
> start_entry_idx);
> - }
> + start_entry_idx = entry->nr;
> + perf_callchain_user(&ctx, regs);
> + fixup_uretprobe_trampoline_entries(entry, start_entry_idx);
> }
>
> +exit_put:
> put_callchain_entry(rctx);
>
> return entry;
> --
> 2.47.2
>
>
