On Thu, Apr 24, 2025 at 01:28:00PM -0400, Steven Rostedt wrote:
> On Thu, 24 Apr 2025 18:36:07 +0200
> Peter Zijlstra <pet...@infradead.org> wrote:
>
> > > +++ 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.
>
> Would there ever be a case where:
>
> current->mm == NULL && !(current->flags & PF_KTHREAD)
>
> ?
>
> That is, do we still need to check for current->mm if it's not a kernel
> thread, or can we assume it exists?
IIRC just checking PF_KTHREAD should be sufficient.
