strace: rewrite restart error handling without sigsetjmp/siglongjmp

Further simplify and optimize error handling of the delay signal handler
by replacing sigsetjmp/siglongjmp mechanism with an error flag.

* strace.c: Do not include <setjmp.h>.
(restart_failed): New volatile variable.
(timer_jmp_buf): Remove.
(next_event): Cache is_delay_timer_created() return value,
remove sigsetjmp invocation, check restart_failed instead.
(timer_sighandler): Replace siglongjmp with setting restart_failed.

diff --git a/strace.c b/strace.c
index 173fdab7be5f70c276d10e61a74cd427991484b1..16b1a8648f5df91ae711fb32b47322ff835e939f 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -34,7 +34,6 @@
 #include <limits.h>
 #include <fcntl.h>
 #include "ptrace.h"
-#include <setjmp.h>
 #include <signal.h>
 #include <sys/resource.h>
 #include <sys/wait.h>
@@ -168,12 +167,11 @@ static void cleanup(void);
 static void interrupt(int sig);
 
 #ifdef HAVE_SIG_ATOMIC_T
-static volatile sig_atomic_t interrupted;
+static volatile sig_atomic_t interrupted, restart_failed;
 #else
-static volatile int interrupted;
+static volatile int interrupted, restart_failed;
 #endif
 
-static jmp_buf timer_jmp_buf;
 static sigset_t timer_set;
 static void timer_sighandler(int);
 
@@ -2238,6 +2236,8 @@ next_event(int *pstatus, siginfo_t *si)
                        return TE_BREAK;
        }
 
+       const bool unblock_delay_timer = is_delay_timer_created();
+
        /*
         * The window of opportunity to handle expirations
         * of the delay timer opens here.
@@ -2245,16 +2245,8 @@ next_event(int *pstatus, siginfo_t *si)
         * Unblock the signal handler for the delay timer
         * iff the delay timer is already created.
         */
-       if (is_delay_timer_created()) {
-               if (sigsetjmp(timer_jmp_buf, 1)) {
-                       /*
-                        * restart_delayed_tcbs() forwarded an error
-                        * from dispatch_event().
-                        */
-                       return TE_BREAK;
-               }
+       if (unblock_delay_timer)
                sigprocmask(SIG_UNBLOCK, &timer_set, NULL);
-       }
 
        /*
         * If the delay timer has expired, then its expiration
@@ -2272,11 +2264,15 @@ next_event(int *pstatus, siginfo_t *si)
         * of the delay timer closes here.
         *
         * Block the signal handler for the delay timer
-        * iff the delay timer is already created.
+        * iff it was unblocked earlier.
         */
-       if (is_delay_timer_created())
+       if (unblock_delay_timer) {
                sigprocmask(SIG_BLOCK, &timer_set, NULL);
 
+               if (restart_failed)
+                       return TE_BREAK;
+       }
+
        if (pid < 0) {
                if (wait_errno == EINTR)
                        return TE_NEXT;
@@ -2611,10 +2607,13 @@ restart_delayed_tcbs(void)
 static void
 timer_sighandler(int sig)
 {
+       if (restart_failed)
+               return;
+
        int saved_errno = errno;
 
        if (!restart_delayed_tcbs())
-               siglongjmp(timer_jmp_buf, 1);
+               restart_failed = 1;
 
        errno = saved_errno;
 }