+ task_stackh-clean-up-stack_not_used-implementation.patch added to mm-new branch

+ task_stackh-clean-up-stack_not_used-implementation.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: task_stack.h: clean-up stack_not_used() implementation
has been added to the -mm mm-new branch.  Its filename is
     task_stackh-clean-up-stack_not_used-implementation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/task_stackh-clean-up-stack_not_used-implementation.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: task_stack.h: clean-up stack_not_used() implementation
Date: Fri, 29 Aug 2025 13:44:41 +0200

Inside the small stack_not_used() function there are several ifdefs for
stack growing-up vs.  regular versions.  Instead just implement this
function two times, one for growing-up and another regular.

Add comments like /* !CONFIG_DEBUG_STACK_USAGE */ to clarify what the
ifdefs are doing.

[linus.walleij@linaro.org: rebased, function moved elsewhere in the kernel]
Link: https://lkml.kernel.org/r/20250829-fork-cleanups-for-dynstack-v1-2-3bbaadce1f00@linaro.org
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/20240311164638.2015063-13-pasha.tatashin@soleen.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Ben Segall <bsegall@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mel Gorman <mgorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/exit.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

--- a/kernel/exit.c~task_stackh-clean-up-stack_not_used-implementation
+++ a/kernel/exit.c
@@ -780,24 +780,29 @@ static void exit_notify(struct task_stru
 }
 
 #ifdef CONFIG_DEBUG_STACK_USAGE
+#ifdef CONFIG_STACK_GROWSUP
 unsigned long stack_not_used(struct task_struct *p)
 {
 	unsigned long *n = end_of_stack(p);
 
 	do {	/* Skip over canary */
-# ifdef CONFIG_STACK_GROWSUP
 		n--;
-# else
-		n++;
-# endif
 	} while (!*n);
 
-# ifdef CONFIG_STACK_GROWSUP
 	return (unsigned long)end_of_stack(p) - (unsigned long)n;
-# else
+}
+#else /* !CONFIG_STACK_GROWSUP */
+unsigned long stack_not_used(struct task_struct *p)
+{
+	unsigned long *n = end_of_stack(p);
+
+	do {	/* Skip over canary */
+		n++;
+	} while (!*n);
+
 	return (unsigned long)n - (unsigned long)end_of_stack(p);
-# endif
 }
+#endif /* CONFIG_STACK_GROWSUP */
 
 /* Count the maximum pages reached in kernel stacks */
 static inline void kstack_histogram(unsigned long used_stack)
@@ -856,9 +861,9 @@ static void check_stack_usage(void)
 	}
 	spin_unlock(&low_water_lock);
 }
-#else
+#else /* !CONFIG_DEBUG_STACK_USAGE */
 static inline void check_stack_usage(void) {}
-#endif
+#endif /* CONFIG_DEBUG_STACK_USAGE */
 
 static void synchronize_group_exit(struct task_struct *tsk, long code)
 {
_

Patches currently in -mm which might be from pasha.tatashin@soleen.com are

fork-check-charging-success-before-zeroing-stack.patch
task_stackh-clean-up-stack_not_used-implementation.patch