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diff -Nrup a/defs.h b/defs.h
--- a/defs.h 2016-05-29 20:29:14.000000000 -0400
+++ b/defs.h 2016-07-22 16:52:17.891092163 -0400
@@ -294,6 +294,9 @@ struct tcb {
int pid; /* If 0, this tcb is free */
int qual_flg; /* qual_flags[scno] or DEFAULT_QUAL_FLAGS + RAW */
int u_error; /* Error code */
+ int wait_status; /* Status from last wait() */
+ struct tcb *next_need_service;
+ /* Linked list of tracees found by wait()s */
long scno; /* System call number */
long u_arg[MAX_ARGS]; /* System call arguments */
#if defined(LINUX_MIPSN32) || defined(X32)
diff -Nrup a/strace.c b/strace.c
--- a/strace.c 2016-05-26 11:34:28.000000000 -0400
+++ b/strace.c 2016-07-22 16:52:17.895092175 -0400
@@ -2095,17 +2095,40 @@ startup_tcb(struct tcb *tcp)
}
}
+static int remembered_pid;
+static int remembered_status;
+
/* Returns true iff the main trace loop has to continue. */
static bool
trace(void)
{
int pid;
+ struct tcb *tcp;
+ struct tcb *found_tcps;
+ struct tcb **nextp;
+ struct tcb *next;
+ int wnohang = 0;
+
+ if (remembered_pid) {
+ pid = remembered_pid;
+ remembered_pid = 0;
+ if (debug_flag)
+ fprintf(stderr, " [remembered wait(%#x) = %u]\n",
+ remembered_status, pid);
+ tcp = pid2tcb(pid); /* can't be NULL */
+ tcp->wait_status = remembered_status;
+ tcp->next_need_service = NULL;
+ found_tcps = tcp;
+ goto process_saved_tcbs;
+ }
+
+ nextp = &found_tcps;
+ found_tcps = NULL;
+
+ while (1) { /* RH 851457 - collect tcbs */
int wait_errno;
int status;
- bool stopped;
- unsigned int sig;
unsigned int event;
- struct tcb *tcp;
struct rusage ru;
if (interrupted)
@@ -2134,14 +2157,24 @@ trace(void)
if (interactive)
sigprocmask(SIG_SETMASK, &empty_set, NULL);
- pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
+ pid = wait4(-1, &status, __WALL | wnohang, (cflag ? &ru : NULL));
wait_errno = errno;
if (interactive)
sigprocmask(SIG_BLOCK, &blocked_set, NULL);
+ if (pid <= 0 && wnohang) {
+ /* We had at least one successful
+ * wait() before. We waited
+ * with WNOHANG second time.
+ * Stop collecting more tracees,
+ * process what we already have.
+ */
+ break; /* out of collect tcbs */
+ }
+
if (pid < 0) {
if (wait_errno == EINTR)
- return true;
+ break; /* out of collect tcbs */
if (nprocs == 0 && wait_errno == ECHILD)
return false;
/*
@@ -2155,7 +2188,7 @@ trace(void)
if (pid == popen_pid) {
if (!WIFSTOPPED(status))
popen_pid = 0;
- return true;
+ break; /* out of collect tcbs */
}
if (debug_flag)
@@ -2167,14 +2200,9 @@ trace(void)
if (!tcp) {
tcp = maybe_allocate_tcb(pid, status);
if (!tcp)
- return true;
+ break; /* out of collect tcbs */
}
- if (WIFSTOPPED(status))
- get_regs(pid);
- else
- clear_regs();
-
event = (unsigned int) status >> 16;
if (event == PTRACE_EVENT_EXEC) {
@@ -2198,29 +2226,86 @@ trace(void)
if (detach_on_execve && !skip_one_b_execve) {
detach(tcp); /* do "-b execve" thingy */
- return true;
+ break; /* out of collect tcbs */
}
skip_one_b_execve = 0;
}
- /* Set current output file */
- current_tcp = tcp;
-
if (cflag) {
tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
tcp->stime = ru.ru_stime;
}
+ /* If we waited and got a stopped task notification,
+ * subsequent wait may return the same pid again, for example,
+ * with SIGKILL notification. SIGKILL kills even stopped tasks.
+ * We must not add it to the list
+ * (one task can't be inserted twice in the list).
+ */
+ {
+ struct tcb *f = found_tcps;
+ while (f) {
+ if (f == tcp) {
+ remembered_pid = pid;
+ remembered_status = status;
+ goto process_saved_tcbs;
+ }
+ f = f->next_need_service;
+ }
+ }
+ /* It is important to not invert the order of tasks
+ * to process. For one, alloc_tcb() above picks newly forked
+ * threads in some order, processing of them and their parent
+ * should be in the same order, otherwise bad things happen
+ * (misinterpreted SIGSTOPs and such).
+ */
+ tcp->wait_status = status;
+ *nextp = tcp;
+ nextp = &tcp->next_need_service;
+ *nextp = NULL;
+ wnohang = WNOHANG;
+
+ } /* RH 851457 - collect tcbs */
+
+process_saved_tcbs:
+
+ for (tcp = found_tcps;
+ tcp;
+ tcp = next) { /* RH 851457 - process tcbs */
+ int status;
+ bool stopped;
+ unsigned int sig;
+ unsigned int event;
+
+ /* If the child exits, the TCP will get dropped and
+ thus we can't use it to find the next TCP needing
+ service. So we save the next TCP needing service
+ and used the saved value when the loop iterates. */
+ next = tcp->next_need_service;
+
+ status = tcp->wait_status;
+ pid = tcp->pid;
+
+ event = ((unsigned)status >> 16);
+
+ if (WIFSTOPPED(status))
+ get_regs(pid);
+ else
+ clear_regs();
+
+ /* Set current output file */
+ current_tcp = tcp;
+
if (WIFSIGNALED(status)) {
print_signalled(tcp, pid, status);
droptcb(tcp);
- return true;
+ continue; /* processing tcbs */
}
if (WIFEXITED(status)) {
print_exited(tcp, pid, status);
droptcb(tcp);
- return true;
+ continue; /* processing tcbs */
}
if (!WIFSTOPPED(status)) {
@@ -2230,7 +2315,7 @@ trace(void)
*/
error_msg("pid %u not stopped!", pid);
droptcb(tcp);
- return true;
+ continue; /* processing tcbs */
}
/* Is this the very first time we see this tracee stopped? */
@@ -2308,7 +2393,7 @@ show_stopsig:
exit_code = 1;
return false;
}
- return true;
+ continue; /* processing tcbs */
}
/* We don't have PTRACE_LISTEN support... */
goto restart_tracee;
@@ -2334,7 +2419,7 @@ show_stopsig:
* we can let this process to report its death to us
* normally, via WIFEXITED or WIFSIGNALED wait status.
*/
- return true;
+ continue; /* processing tcbs */
}
restart_tracee_with_sig_0:
@@ -2347,6 +2432,8 @@ restart_tracee:
return false;
}
+ } /* RH 851457 - process tcbs */
+
return true;
}