fix power of two computation

diff --git a/libust/tracectl.c b/libust/tracectl.c
index 39756a55fec0e72602479593fce153408fc950d5..3624b867f6d9f7a39bcae586878b00ae3abdd0b2 100644 (file)
--- a/libust/tracectl.c
+++ b/libust/tracectl.c
@@ -456,18 +456,18 @@ static int do_cmd_get_subbuf_size(const char *recvbuf, struct ustcomm_source *sr
        return retval;
 }
 
-static unsigned int poweroftwo(unsigned int x)
-{
-    unsigned int power2 = 1;
-    unsigned int hardcoded = 2147483648u; /* FIX max 2^31 */
-
-    if (x < 2)
-        return 2;
+/* Return the power of two which is equal or higher to v */
 
-    while (power2 < x && power2 < hardcoded)
-        power2 *= 2;
-
-    return power2;
+static unsigned int pow2_higher_or_eq(unsigned int v)
+{
+       int hb = fls(v);
+       int hbm1 = hb-1;
+       int retval = 1<<(hb-1);
+
+       if(v-retval == 0)
+               return retval;
+       else
+               return retval<<1;
 }
 
 static int do_cmd_set_subbuf_size(const char *recvbuf, struct ustcomm_source *src)
@@ -491,9 +491,10 @@ static int do_cmd_set_subbuf_size(const char *recvbuf, struct ustcomm_source *sr
                goto end;
        }
 
-       power = poweroftwo(size);
+       power = pow2_higher_or_eq(size);
+       power = max_t(unsigned int, 2u, power);
        if (power != size)
-               WARN("using the next 2^n = %u\n", power);
+               WARN("using the next power of two for buffer size = %u\n", power);
 
        ltt_lock_traces();
        trace = _ltt_trace_find_setup(trace_name);