[PATCH 7/9] cpumask: define cleanup function for cpumasks

[Yury Norov]

Now we can simplify a code that allocates cpumasks for local needs.

Automatic variables have to be initialized at declaration, or at least
before any possibility for the logic to return, so that compiler
wouldn't try to call an associate destructor function on a random stack
number.

Because cpumask_var_t, depending on the CPUMASK_OFFSTACK config, is
either a pointer or an array, we have to have a macro for initialization.

So define a CPUMASK_NULL macro, which allows to init struct cpumask
pointer with NULL when CPUMASK_OFFSTACK is enabled, and effectively
a no-op when CPUMASK_OFFSTACK is disabled.

Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
---
 include/linux/cpumask.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 73ff2e0ef090..0dd8e810200f 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -7,6 +7,7 @@
  * set of CPUs in a system, one bit position per CPU number.  In general,
  * only nr_cpu_ids (<= NR_CPUS) bits are valid.
  */
+#include <linux/cleanup.h>
 #include <linux/kernel.h>
 #include <linux/threads.h>
 #include <linux/bitmap.h>
@@ -898,6 +899,7 @@ typedef struct cpumask *cpumask_var_t;
 
 #define this_cpu_cpumask_var_ptr(x)	this_cpu_read(x)
 #define __cpumask_var_read_mostly	__read_mostly
+#define CPUMASK_NULL			NULL
 
 bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node);
 
@@ -945,6 +947,7 @@ typedef struct cpumask cpumask_var_t[1];
 
 #define this_cpu_cpumask_var_ptr(x) this_cpu_ptr(x)
 #define __cpumask_var_read_mostly
+#define CPUMASK_NULL {}
 
 static inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
 {
@@ -988,6 +991,8 @@ static inline bool cpumask_available(cpumask_var_t mask)
 }
 #endif /* CONFIG_CPUMASK_OFFSTACK */
 
+DEFINE_FREE(free_cpumask_var, struct cpumask *, if (_T) free_cpumask_var(_T));
+
 /* It's common to want to use cpu_all_mask in struct member initializers,
  * so it has to refer to an address rather than a pointer. */
 extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS);
-- 
2.40.1