block all signals in listener thread

[ust.git] / libust / tracectl.c

diff --git a/libust/tracectl.c b/libust/tracectl.c
index 74ad4ea6be59a309ab8a4634ae7af15d48725d2b..7a5cf9562282ce7fe90cc3d5e4c405d3bf44b8c6 100644 (file)
--- a/libust/tracectl.c
+++ b/libust/tracectl.c
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
+#include <pthread.h>
 #include <signal.h>
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -456,18 +457,18 @@ 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 = 2147483648; /* FIX max 2^31 */
-
-    if (x < 2)
-        return 2;
-
-    while (power2 < x && power2 < hardcoded)
-        power2 *= 2;
+/* Return the power of two which is equal or higher to v */
 
-    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 +492,10 @@ 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);
@@ -1030,17 +1032,38 @@ static pthread_t listener_thread;
 void create_listener(void)
 {
        int result;
+       sigset_t sig_all_blocked;
+       sigset_t orig_parent_mask;
 
        if(have_listener) {
                WARN("not creating listener because we already had one");
                return;
        }
 
+       /* A new thread created by pthread_create inherits the signal mask
+        * from the parent. To avoid any signal being received by the
+        * listener thread, we block all signals temporarily in the parent,
+        * while we create the listener thread.
+        */
+
+       sigfillset(&sig_all_blocked);
+
+       result = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
+       if(result) {
+               PERROR("pthread_sigmask: %s", strerror(result));
+       }
+
        result = pthread_create(&listener_thread, NULL, listener_main, NULL);
        if(result == -1) {
                PERROR("pthread_create");
        }
 
+       /* Restore original signal mask in parent */
+       result = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
+       if(result) {
+               PERROR("pthread_sigmask: %s", strerror(result));
+       }
+
        have_listener = 1;
 }