'deadline.c' uses housekeeping APIs but relies on transitive
includes for their declarations.

With stricter include checking, this can fail to build, for example: 
  error: implicit declaration of function 'housekeeping_enabled'

Include `<linux/sched/isolation.h>` directly in `deadline.c` so required
housekeeping interfaces are declared at the use site.

Reproducer (without this patch):
  make KCFLAGS="-Werror=implicit-function-declaration" \
       kernel/sched/deadline.o

This fails with:
  error: implicit declaration of function 'housekeeping_cpumask'
  error: 'HK_TYPE_DOMAIN' undeclared
  error: implicit declaration of function 'housekeeping_enabled'

After applying this patch, the same command builds 
`kernel/sched/deadline.o` successfully.

Fixes: 318e18ed22e8 ("sched/deadline: Walk up cpuset hierarchy to decide root domain when hot-unplug")
Cc: stable@vger.kernel.org
Assisted-by: Codex:GPT-5
Signed-off-by: Joseph Salisbury <joseph.salisbury@oracle.com>
---
 kernel/sched/deadline.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d08b00429323..75d5263518f5 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/cpuset.h>
+#include <linux/sched/isolation.h>
 #include <linux/sched/clock.h>
 #include <uapi/linux/sched/types.h>
 #include "sched.h"
-- 
2.47.3