diff --git a/example/generator/odp_generator.c b/example/generator/odp_generator.c
index 03dab50..2433cb6 100644
--- a/example/generator/odp_generator.c
+++ b/example/generator/odp_generator.c
@@ -545,7 +545,7 @@ int main(int argc, char *argv[])
 	int i;
 	odp_shm_t shm;
 	odp_cpumask_t cpumask;
-	char cpumaskstr[64];
+	char cpumaskstr[ODP_CPUMASK_BUFSIZE];
 	odp_pool_param_t params;
 
 	/* Init ODP before calling anything else */
@@ -596,7 +596,7 @@ int main(int argc, char *argv[])
 	 * Start mapping thread from CPU #1
 	 */
 	num_workers = odph_linux_cpumask_default(&cpumask, num_workers);
-	odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
+	(void)odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
 
 	printf("num worker threads: %i\n", num_workers);
 	printf("first CPU:          %i\n", odp_cpumask_first(&cpumask));
diff --git a/example/ipsec/odp_ipsec.c b/example/ipsec/odp_ipsec.c
index 03f2419..869fd3a 100644
--- a/example/ipsec/odp_ipsec.c
+++ b/example/ipsec/odp_ipsec.c
@@ -1193,7 +1193,7 @@ main(int argc, char *argv[])
 	int stream_count;
 	odp_shm_t shm;
 	odp_cpumask_t cpumask;
-	char cpumaskstr[64];
+	char cpumaskstr[ODP_CPUMASK_BUFSIZE];
 	odp_pool_param_t params;
 
 	/* Init ODP before calling anything else */
@@ -1242,7 +1242,7 @@ main(int argc, char *argv[])
 	 * Start mapping thread from CPU #1
 	 */
 	num_workers = odph_linux_cpumask_default(&cpumask, num_workers);
-	odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
+	(void)odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
 
 	printf("num worker threads: %i\n", num_workers);
 	printf("first CPU:          %i\n", odp_cpumask_first(&cpumask));
diff --git a/example/l2fwd/odp_l2fwd.c b/example/l2fwd/odp_l2fwd.c
index 7a520fb..e22ec0c 100644
--- a/example/l2fwd/odp_l2fwd.c
+++ b/example/l2fwd/odp_l2fwd.c
@@ -294,7 +294,7 @@ int main(int argc, char *argv[])
 	int num_workers;
 	odp_shm_t shm;
 	odp_cpumask_t cpumask;
-	char cpumaskstr[64];
+	char cpumaskstr[ODP_CPUMASK_BUFSIZE];
 	odp_pool_param_t params;
 
 	/* Init ODP before calling anything else */
@@ -336,7 +336,7 @@ int main(int argc, char *argv[])
 	 * Start mapping thread from CPU #1
 	 */
 	num_workers = odph_linux_cpumask_default(&cpumask, num_workers);
-	odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
+	(void)odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
 
 	printf("num worker threads: %i\n", num_workers);
 	printf("first CPU:          %i\n", odp_cpumask_first(&cpumask));
diff --git a/example/packet/odp_pktio.c b/example/packet/odp_pktio.c
index 28ed98c..e38029a 100644
--- a/example/packet/odp_pktio.c
+++ b/example/packet/odp_pktio.c
@@ -287,7 +287,7 @@ int main(int argc, char *argv[])
 	int i;
 	int cpu;
 	odp_cpumask_t cpumask;
-	char cpumaskstr[64];
+	char cpumaskstr[ODP_CPUMASK_BUFSIZE];
 	odp_pool_param_t params;
 
 	args = calloc(1, sizeof(args_t));
@@ -324,7 +324,7 @@ int main(int argc, char *argv[])
 	 * Start mapping thread from CPU #1
 	 */
 	num_workers = odph_linux_cpumask_default(&cpumask, num_workers);
-	odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
+	(void)odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
 
 	printf("num worker threads: %i\n", num_workers);
 	printf("first CPU:          %i\n", odp_cpumask_first(&cpumask));
diff --git a/example/timer/odp_timer_test.c b/example/timer/odp_timer_test.c
index 0df041f..299ed89 100644
--- a/example/timer/odp_timer_test.c
+++ b/example/timer/odp_timer_test.c
@@ -317,7 +317,7 @@ int main(int argc, char *argv[])
 	odp_timer_pool_param_t tparams;
 	odp_timer_pool_info_t tpinfo;
 	odp_cpumask_t cpumask;
-	char cpumaskstr[64];
+	char cpumaskstr[ODP_CPUMASK_BUFSIZE];
 
 	printf("\nODP timer example starts\n");
 
@@ -358,7 +358,7 @@ int main(int argc, char *argv[])
 	 * Start mapping thread from CPU #1
 	 */
 	num_workers = odph_linux_cpumask_default(&cpumask, num_workers);
-	odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
+	(void)odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
 
 	printf("num worker threads: %i\n", num_workers);
 	printf("first CPU:          %i\n", odp_cpumask_first(&cpumask));
diff --git a/include/odp/api/cpumask.h b/include/odp/api/cpumask.h
index 7482899..409f3b4 100644
--- a/include/odp/api/cpumask.h
+++ b/include/odp/api/cpumask.h
@@ -18,12 +18,20 @@
 extern "C" {
 #endif
 
+#include <sys/types.h>
+#include <odp/config.h>
+
 /** @addtogroup odp_scheduler
  *  CPU mask operations.
  *  @{
  */
 
- /**
+/**
+ * @def ODP_CPUMASK_BUFSIZE
+ * Minimum size of output buffer for odp_cpumask_to_str()
+ */
+
+/**
  * Add CPU mask bits from a string
  *
  * @param mask   CPU mask to modify
@@ -33,13 +41,16 @@ extern "C" {
 void odp_cpumask_from_str(odp_cpumask_t *mask, const char *str);
 
 /**
- * Write CPU mask as a string of hexadecimal digits
+ * Format CPU mask as a string of hexadecimal digits
+ *
+ * @param mask CPU mask to format
+ * @param[out] str Output buffer (use ODP_CPUMASK_BUFSIZE)
+ * @param size Size of output buffer
  *
- * @param mask   CPU mask
- * @param str    String for output
- * @param len    Size of string length (incl. ending zero)
+ * @return number of characters written (including terminating null char)
+ * @retval <0 on failure (buffer too small)
  */
-void odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, int len);
+ssize_t odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, ssize_t size);
 
 /**
  * Clear entire mask
diff --git a/platform/linux-generic/include/odp/plat/cpumask_types.h b/platform/linux-generic/include/odp/plat/cpumask_types.h
index 6d9e129..20626f0 100644
--- a/platform/linux-generic/include/odp/plat/cpumask_types.h
+++ b/platform/linux-generic/include/odp/plat/cpumask_types.h
@@ -25,6 +25,11 @@ extern "C" {
 #include <odp/std_types.h>
 
 /**
+ * Minimum size of output buffer for odp_cpumask_to_str()
+ */
+#define ODP_CPUMASK_BUFSIZE ((ODP_CONFIG_MAX_THREADS + 3) / 4 + 3)
+
+/**
  * CPU mask
  *
  * Don't access directly, use access functions.
diff --git a/platform/linux-generic/odp_cpumask.c b/platform/linux-generic/odp_cpumask.c
index 6088ca2..0bae1ce 100644
--- a/platform/linux-generic/odp_cpumask.c
+++ b/platform/linux-generic/odp_cpumask.c
@@ -8,6 +8,7 @@
 #define _GNU_SOURCE
 #endif
 #include <sched.h>
+#include <sys/types.h>
 
 #include <odp/cpumask.h>
 #include <odp_debug_internal.h>
@@ -60,29 +61,31 @@ void odp_cpumask_from_str(odp_cpumask_t *mask, const char *str_in)
 	memcpy(&mask->set, &cpuset, sizeof(cpuset));
 }
 
-void odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, int len)
+ssize_t odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, ssize_t len)
 {
 	char *p = str;
 	int cpu = odp_cpumask_last(mask);
-	int nibbles;
+	unsigned int nibbles;
 	int value;
 
-	/* Quickly handle bad string length or empty mask */
-	if (len <= 0)
-		return;
-	*str = 0;
+	/* Handle bad string length, need at least 4 chars for "0x0" and
+	 * terminating null char */
+	if (len < 4)
+		return -1; /* Failure */
+
+	/* Handle no CPU found */
 	if (cpu < 0) {
-		if (len >= 4)
-			strcpy(str, "0x0");
-		return;
+		strcpy(str, "0x0");
+		return strlen(str) + 1; /* Success */
 	}
+	/* CPU was found and cpu >= 0 */
 
-	/* Compute number nibbles in cpumask that have bits set */
+	/* Compute number of nibbles in cpumask that have bits set */
 	nibbles = (cpu / 4) + 1;
 
 	/* Verify minimum space (account for "0x" and termination) */
 	if (len < (3 + nibbles))
-		return;
+		return -1; /* Failure */
 
 	/* Prefix */
 	*p++ = '0';
@@ -110,6 +113,7 @@ void odp_cpumask_to_str(const odp_cpumask_t *mask, char *str, int len)
 
 	/* Terminate the string */
 	*p++ = 0;
+	return p - str; /* Success */
 }
 
 void odp_cpumask_zero(odp_cpumask_t *mask)
diff --git a/test/api_test/odp_common.c b/test/api_test/odp_common.c
index 5f9504c..b5f2d4d 100644
--- a/test/api_test/odp_common.c
+++ b/test/api_test/odp_common.c
@@ -30,14 +30,14 @@ __thread test_shared_data_t *test_shared_data;	    /**< pointer to shared data *
 void odp_print_system_info(void)
 {
 	odp_cpumask_t cpumask;
-	char str[32];
+	char str[ODP_CPUMASK_BUFSIZE];
 
 	memset(str, 1, sizeof(str));
 
 	odp_cpumask_zero(&cpumask);
 
 	odp_cpumask_from_str(&cpumask, "0x1");
-	odp_cpumask_to_str(&cpumask, str, sizeof(str));
+	(void)odp_cpumask_to_str(&cpumask, str, sizeof(str));
 
 	printf("\n");
 	printf("ODP system info\n");
diff --git a/test/performance/odp_scheduling.c b/test/performance/odp_scheduling.c
index 3d7167f..ba13d8e 100644
--- a/test/performance/odp_scheduling.c
+++ b/test/performance/odp_scheduling.c
@@ -828,7 +828,7 @@ int main(int argc, char *argv[])
 	int prios;
 	odp_shm_t shm;
 	test_globals_t *globals;
-	char cpumaskstr[64];
+	char cpumaskstr[ODP_CPUMASK_BUFSIZE];
 	odp_pool_param_t params;
 
 	printf("\nODP example starts\n\n");
@@ -879,7 +879,7 @@ int main(int argc, char *argv[])
 	 * Start mapping thread from CPU #1
 	 */
 	num_workers = odph_linux_cpumask_default(&cpumask, num_workers);
-	odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
+	(void)odp_cpumask_to_str(&cpumask, cpumaskstr, sizeof(cpumaskstr));
 
 	printf("num worker threads: %i\n", num_workers);
 	printf("first CPU:          %i\n", odp_cpumask_first(&cpumask));
