perf cpumap: Convert cpu_map.refcnt from atomic_t to refcount_t

The refcount_t type and corresponding API should be used instead of atomic_t
when the variable is used as a reference counter.

This allows to avoid accidental refcounter overflows that might lead to
use-after-free situations.

Signed-off-by: Elena Reshetova <[e-mail]>
Signed-off-by: David Windsor <[e-mail]>
Signed-off-by: Hans Liljestrand <[e-mail]>
Signed-off-by: Kees Kook <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: David Windsor <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Hans Liljestrand <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kees Kook <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Matija Glavinic Pecotic <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
[ fixed mixed conversion to refcount in tests/cpumap.c ]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/cpumap.c

···
 	TEST_ASSERT_VAL("wrong nr",  map->nr == 2);
 	TEST_ASSERT_VAL("wrong cpu", map->map[0] == 1);
 	TEST_ASSERT_VAL("wrong cpu", map->map[1] == 256);
-	TEST_ASSERT_VAL("wrong refcnt", atomic_read(&map->refcnt) == 1);
+	TEST_ASSERT_VAL("wrong refcnt", refcount_read(&map->refcnt) == 1);
 	cpu_map__put(map);
 	return 0;
 }

tools/perf/util/cpumap.c

···
 			cpus->map[i] = i;
 
 		cpus->nr = nr_cpus;
-		atomic_set(&cpus->refcnt, 1);
+		refcount_set(&cpus->refcnt, 1);
 	}
 
 	return cpus;
···
 	if (cpus != NULL) {
 		cpus->nr = nr_cpus;
 		memcpy(cpus->map, tmp_cpus, payload_size);
-		atomic_set(&cpus->refcnt, 1);
+		refcount_set(&cpus->refcnt, 1);
 	}
 
 	return cpus;
···
 	if (cpus != NULL) {
 		cpus->nr = 1;
 		cpus->map[0] = -1;
-		atomic_set(&cpus->refcnt, 1);
+		refcount_set(&cpus->refcnt, 1);
 	}
 
 	return cpus;
···
 		for (i = 0; i < nr; i++)
 			cpus->map[i] = -1;
 
-		atomic_set(&cpus->refcnt, 1);
+		refcount_set(&cpus->refcnt, 1);
 	}
 
 	return cpus;
···
 static void cpu_map__delete(struct cpu_map *map)
 {
 	if (map) {
-		WARN_ONCE(atomic_read(&map->refcnt) != 0,
+		WARN_ONCE(refcount_read(&map->refcnt) != 0,
 			  "cpu_map refcnt unbalanced\n");
 		free(map);
 	}
···
 struct cpu_map *cpu_map__get(struct cpu_map *map)
 {
 	if (map)
-		atomic_inc(&map->refcnt);
+		refcount_inc(&map->refcnt);
 	return map;
 }
 
 void cpu_map__put(struct cpu_map *map)
 {
-	if (map && atomic_dec_and_test(&map->refcnt))
+	if (map && refcount_dec_and_test(&map->refcnt))
 		cpu_map__delete(map);
 }
 
···
 	/* ensure we process id in increasing order */
 	qsort(c->map, c->nr, sizeof(int), cmp_ids);
 
-	atomic_set(&c->refcnt, 1);
+	refcount_set(&c->refcnt, 1);
 	*res = c;
 	return 0;
 }

tools/perf/util/cpumap.h

···
 
 #include <stdio.h>
 #include <stdbool.h>
-#include <linux/atomic.h>
+#include <linux/refcount.h>
 
 #include "perf.h"
 #include "util/debug.h"
 
 struct cpu_map {
-	atomic_t refcnt;
+	refcount_t refcnt;
 	int nr;
 	int map[];
 };