Improve error messages in detach()

* strace.c (detach): Change return type from int to void.
Improve error meesages: show PID, tell exactly which operation fails.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

diff --git a/strace.c b/strace.c
index e94ca31c9bdf0bfc639088323cef557c335c7b10..ae24db12f420ab2e8a053a14e9b63636cf3190a1 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -157,7 +157,7 @@ static const char *progname;
 
 unsigned os_release; /* generated from uname()'s u.release */
 
-static int detach(struct tcb *tcp);
+static void detach(struct tcb *tcp);
 static int trace(void);
 static void cleanup(void);
 static void interrupt(int sig);
@@ -729,7 +729,7 @@ droptcb(struct tcb *tcp)
  * attached-unstopped processes give the same ESRCH.  For unattached process we
  * would SIGSTOP it and wait for its SIGSTOP notification forever.
  */
-static int
+static void
 detach(struct tcb *tcp)
 {
        int error;
@@ -764,14 +764,14 @@ detach(struct tcb *tcp)
                }
                else if (errno != ESRCH) {
                        /* Shouldn't happen. */
-                       perror_msg("detach: ptrace(PTRACE_DETACH, ...)");
+                       perror_msg("detach: ptrace(%u,PTRACE_DETACH)", tcp->pid);
                }
                else
                /* ESRCH: process is either not stopped or doesn't exist. */
                if (my_tkill(tcp->pid, 0) < 0) {
                        if (errno != ESRCH)
                                /* Shouldn't happen. */
-                               perror_msg("detach: checking sanity");
+                               perror_msg("detach: tkill(%u,0)", tcp->pid);
                        /* else: process doesn't exist. */
                }
                else
@@ -788,17 +788,15 @@ detach(struct tcb *tcp)
                                error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
                                if (!error)
                                        interrupt_done = 1;
+                               else if (errno != ESRCH)
+                                       perror_msg("detach: ptrace(%u,PTRACE_INTERRUPT)", tcp->pid);
                        }
                        else {
                                error = my_tkill(tcp->pid, SIGSTOP);
                                if (!error)
                                        sigstop_expected = 1;
-                       }
-                       if (error && errno != ESRCH) {
-                               if (use_seize)
-                                       perror_msg("detach: ptrace(PTRACE_INTERRUPT, ...)");
-                               else
-                                       perror_msg("detach: stopping child");
+                               else if (errno != ESRCH)
+                                       perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
                        }
                }
        }
@@ -811,7 +809,7 @@ detach(struct tcb *tcp)
                                        continue;
                                if (errno == ECHILD) /* Already gone.  */
                                        break;
-                               perror_msg("detach: waiting");
+                               perror_msg("detach: waitpid(%u)", tcp->pid);
                                break;
                        }
                        if (!WIFSTOPPED(status)) {
@@ -870,8 +868,6 @@ detach(struct tcb *tcp)
                fprintf(stderr, "Process %u detached\n", tcp->pid);
 
        droptcb(tcp);
-
-       return error;
 }
 
 static void