[RFC 2/3] sched: add type checks to for_each_cpu_mask()

[Sasha Levin <levinsasha928@gmail.com>]

Add type checks to assert that 'mask' is 'struct cpumask *'. This check
would have detected the bug fixed in e3831ed ("sched: Fix incorrect usage
of for_each_cpu_mask() in select_fallback_rq()"):

kernel/sched/core.c: In function 'select_fallback_rq':
kernel/sched/core.c:1273:2: warning: comparison of distinct pointer types lacks a cast
kernel/sched/core.c:1284:3: warning: comparison of distinct pointer types lacks a cast

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 include/linux/cpumask.h |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index a2c819d..58fd022 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -799,7 +799,8 @@ static inline const struct cpumask *get_cpu_mask(unsigned int cpu)
 #define first_cpu(src)		({ (void)(src); 0; })
 #define next_cpu(n, src)	({ (void)(src); 1; })
 #define any_online_cpu(mask)	0
-#define for_each_cpu_mask(cpu, mask)	\
+#define for_each_cpu_mask(cpu, mask)		\
+	typecheck(struct cpumask *, (mask));	\
 	for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
 #else /* NR_CPUS > 1 */
 int __first_cpu(const cpumask_t *srcp);
@@ -809,6 +810,7 @@ int __next_cpu(int n, const cpumask_t *srcp);
 #define next_cpu(n, src)	__next_cpu((n), &(src))
 #define any_online_cpu(mask) cpumask_any_and(&mask, cpu_online_mask)
 #define for_each_cpu_mask(cpu, mask)			\
+	typecheck(struct cpumask *, (mask));		\
 	for ((cpu) = -1;				\
 		(cpu) = next_cpu((cpu), (mask)),	\
 		(cpu) < NR_CPUS; )
-- 
1.7.8.5