On Wed, May 20, 2026 at 02:04:01PM +0200, Frederic Weisbecker wrote: > Le Tue, May 19, 2026 at 09:01:28PM +0200, Arnd Bergmann a écrit : > > From: Arnd Bergmann <[email protected]> > > > > When CONFIG_UBSAN_ALIGNMENT is enabled, the stack usage of nocb_gp_wait() > > grows above typical warning limits: > > > > In file included from kernel/rcu/tree.c:4930: > > kernel/rcu/tree_nocb.h: In function 'rcu_nocb_gp_kthread': > > kernel/rcu/tree_nocb.h:866:1: error: the frame size of 1968 bytes is larger > > than 1280 bytes [-Werror=frame-larger-than=] > > > > Apparently, the problem is passing rcu_data from a 'void *' pointer, > > which gcc assumes may be misaligned. When the function is not inlined > > into rcu_nocb_gp_kthread(), that is no longer visible to gcc. > > > > Add a 'noinline_for_stack' annotation that leads to skipping a lot of > > the alignment sanitizer checks and keeps the stack usage 60% lower here. > > > > Signed-off-by: Arnd Bergmann <[email protected]> > > --- > > kernel/rcu/tree_nocb.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > > index 1047b30cd46b..373b877cf171 100644 > > --- a/kernel/rcu/tree_nocb.h > > +++ b/kernel/rcu/tree_nocb.h > > @@ -655,7 +655,7 @@ static void nocb_gp_sleep(struct rcu_data *my_rdp, int > > cpu) > > * No-CBs GP kthreads come here to wait for additional callbacks to show up > > * or for grace periods to end. > > */ > > -static void nocb_gp_wait(struct rcu_data *my_rdp) > > +static noinline_for_stack void nocb_gp_wait(struct rcu_data *my_rdp) > > This probably deserve a comment though. > > Other than that: > > Reviewed-by: Frederic Weisbecker <[email protected]> > Took the patch and applied the tag from both!
-- Uladzislau Rezki
