Do not block handled signals in interactive mode

Let these signals be handled asynchronously as they are acted on
only when waiting for process state changes.

* strace.c (start_set, blocked_set): Remove.
(set_sighandler): Do not update blocked_set.
(startup_attach, init, next_event): Remove all sigprocmask calls.

diff --git a/strace.c b/strace.c
index 9f2f4c68689b1b02515410b69327fdd34b181285..e7da26f10fe5cccec2e0d58110825797259019e7 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -165,7 +165,6 @@ unsigned os_release; /* generated from uname()'s u.release */
 static void detach(struct tcb *tcp);
 static void cleanup(void);
 static void interrupt(int sig);
-static sigset_t start_set, blocked_set;
 
 #ifdef HAVE_SIG_ATOMIC_T
 static volatile sig_atomic_t interrupted;
@@ -1081,15 +1080,6 @@ startup_attach(void)
        unsigned int tcbi;
        struct tcb *tcp;
 
-       /*
-        * Block user interruptions as we would leave the traced
-        * process stopped (process state T) if we would terminate in
-        * between PTRACE_ATTACH and wait4() on SIGSTOP.
-        * We rely on cleanup() from this point on.
-        */
-       if (interactive)
-               sigprocmask(SIG_SETMASK, &blocked_set, NULL);
-
        if (daemonized_tracer) {
                pid_t pid = fork();
                if (pid < 0)
@@ -1129,12 +1119,8 @@ startup_attach(void)
 
                attach_tcb(tcp);
 
-               if (interactive) {
-                       sigprocmask(SIG_SETMASK, &start_set, NULL);
-                       if (interrupted)
-                               goto ret;
-                       sigprocmask(SIG_SETMASK, &blocked_set, NULL);
-               }
+               if (interrupted)
+                       return;
        } /* for each tcbtab[] */
 
        if (daemonized_tracer) {
@@ -1145,10 +1131,6 @@ startup_attach(void)
                kill(parent_pid, SIGKILL);
                strace_child = 0;
        }
-
- ret:
-       if (interactive)
-               sigprocmask(SIG_SETMASK, &start_set, NULL);
 }
 
 /* Stack-o-phobic exec helper, in the hope to work around
@@ -1553,10 +1535,6 @@ get_os_release(void)
 static void
 set_sighandler(int signo, void (*sighandler)(int), struct sigaction *oldact)
 {
-       /* if signal handler is a function, add the signal to blocked_set */
-       if (sighandler != SIG_IGN && sighandler != SIG_DFL)
-               sigaddset(&blocked_set, signo);
-
        const struct sigaction sa = { .sa_handler = sighandler };
        sigaction(signo, &sa, oldact);
 }
@@ -1779,9 +1757,6 @@ init(int argc, char *argv[])
        memset(acolumn_spaces, ' ', acolumn);
        acolumn_spaces[acolumn] = '\0';
 
-       sigprocmask(SIG_SETMASK, NULL, &start_set);
-       memcpy(&blocked_set, &start_set, sizeof(blocked_set));
-
        set_sighandler(SIGCHLD, SIG_DFL, &params_for_tracee.child_sa);
 
 #ifdef USE_LIBUNWIND
@@ -1895,9 +1870,9 @@ init(int argc, char *argv[])
                        set_sighandler(SIGTSTP, SIG_IGN, NULL);
                /*
                 * In interactive mode (if no -o OUTFILE, or -p PID is used),
-                * fatal signals are blocked while syscall stop is processed,
-                * and acted on in between, when waiting for new syscall stops.
-                * In non-interactive mode, signals are ignored.
+                * fatal signals are handled asynchronously and acted
+                * when waiting for process state changes.
+                * In non-interactive mode these signals are ignored.
                 */
                set_sighandler(SIGHUP, interactive ? interrupt : SIG_IGN, NULL);
                set_sighandler(SIGINT, interactive ? interrupt : SIG_IGN, NULL);
@@ -2225,7 +2200,6 @@ static enum trace_event
 next_event(int *pstatus, siginfo_t *si)
 {
        int pid;
-       int wait_errno;
        int status;
        struct tcb *tcp;
        struct rusage ru;
@@ -2254,23 +2228,16 @@ next_event(int *pstatus, siginfo_t *si)
                        return TE_BREAK;
        }
 
-       if (interactive)
-               sigprocmask(SIG_SETMASK, &start_set, NULL);
        pid = wait4(-1, pstatus, __WALL, (cflag ? &ru : NULL));
-       wait_errno = errno;
-       if (interactive)
-               sigprocmask(SIG_SETMASK, &blocked_set, NULL);
-
        if (pid < 0) {
-               if (wait_errno == EINTR)
+               if (errno == EINTR)
                        return TE_NEXT;
-               if (nprocs == 0 && wait_errno == ECHILD)
+               if (nprocs == 0 && errno == ECHILD)
                        return TE_BREAK;
                /*
                 * If nprocs > 0, ECHILD is not expected,
                 * treat it as any other error here:
                 */
-               errno = wait_errno;
                perror_msg_and_die("wait4(__WALL)");
        }