1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/gpu/nvgpu/os/posix/bitmap.c b/drivers/gpu/nvgpu/os/posix/bitmap.c
index f25f6e64..99ba62c3 100644
--- a/drivers/gpu/nvgpu/os/posix/bitmap.c
+++ b/drivers/gpu/nvgpu/os/posix/bitmap.c
@@ -37,7 +37,18 @@ unsigned long __nvgpu_posix_ffs(unsigned long word)
 
 unsigned long __nvgpu_posix_fls(unsigned long word)
 {
-        return ((sizeof(unsigned long) * 8UL) - 1UL) - __builtin_clzl(word);
+        unsigned long ret;
+
+        if (word == 0UL) {
+                /* __builtin_clzl() below is undefined for 0, so we have
+                 * to handle that as a special case.
+                 */
+                ret = 0UL;
+        } else {
+                ret = (sizeof(unsigned long) * 8UL) - __builtin_clzl(word);
+        }
+
+        return ret;
 }
 
 static unsigned long __find_next_bit(const unsigned long *addr,