On Wed, Jan 22, 2025 at 03:29:10PM +0100, Peter Zijlstra wrote: > On Tue, Jan 21, 2025 at 06:31:26PM -0800, Josh Poimboeuf wrote: > > If the task doesn't have any memory, there's no stack to unwind. > > > > Signed-off-by: Josh Poimboeuf <[email protected]> > > --- > > 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 99f0f28feeb5..a886bb83f4d0 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -7792,7 +7792,7 @@ 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; > > What about things like io_uring helpers, don't they keep ->mm but are > never in userspace?
Hm, that's news to me. At least this patch doesn't make things worse in that regard. IIRC, user_regs(task_pt_regs(current)) returns false for kthreads because the regs area is cleared. We could add in a user_regs() check? -- Josh
