Re: [Crash-utility] crash CPU bound waiting for user response
| From: Dave Anderson <anderson(a)redhat.com>
| Yeah, but I'm still paranoid about re-introducing the hang I used
| to see.
|
| I think I'll just put a "stall(1000);" call after each waitpid().
| Works for me...
I take that as a challenge. I think that I've eliminated this
busy-wait and simplified the code. I admit that wait_for_children is
slightly more complicated.
In light testing this worked fine. I'd really like to find out how
this is going to hang. I promise to attempt to debug any hang that I
can duplicate.
===================================================================
RCS file: RCS/cmdline.c,v
retrieving revision 1.1
diff -u -r1.1 cmdline.c
--- cmdline.c 2007/07/10 19:30:01 1.1
+++ cmdline.c 2007/07/10 20:16:57
@@ -31,6 +31,7 @@
static void set_my_tty(void);
static char *signame(int);
static int setup_stdpipe(void);
+static void wait_for_child(pid_t *);
static void wait_for_children(ulong);
#define ZOMBIES_ONLY (1)
#define ALL_CHILDREN (2)
@@ -878,25 +879,15 @@
if (pc->stdpipe) {
close(fileno(pc->stdpipe));
pc->stdpipe = NULL;
- if (pc->stdpipe_pid && PID_ALIVE(pc->stdpipe_pid)) {
- while (!waitpid(pc->stdpipe_pid, &waitstatus, WNOHANG))
- ;
- }
- pc->stdpipe_pid = 0;
+ wait_for_child(&pc->stdpipe_pid);
}
if (pc->pipe) {
close(fileno(pc->pipe));
pc->pipe = NULL;
console("wait for redirect %d->%d to finish...\n",
pc->pipe_shell_pid, pc->pipe_pid);
- if (pc->pipe_pid)
- while (PID_ALIVE(pc->pipe_pid))
- waitpid(pc->pipe_pid, &waitstatus, WNOHANG);
- if (pc->pipe_shell_pid)
- while (PID_ALIVE(pc->pipe_shell_pid))
- waitpid(pc->pipe_shell_pid,
- &waitstatus, WNOHANG);
- pc->pipe_pid = 0;
+ wait_for_child(&pc->pipe_pid);
+ wait_for_child(&pc->pipe_shell_pid);
}
if (pc->ifile_pipe) {
fflush(pc->ifile_pipe);
@@ -907,12 +898,8 @@
(FROM_INPUT_FILE|REDIRECT_TO_PIPE|REDIRECT_PID_KNOWN))) {
console("wait for redirect %d->%d to finish...\n",
pc->pipe_shell_pid, pc->pipe_pid);
- while (PID_ALIVE(pc->pipe_pid))
- waitpid(pc->pipe_pid, &waitstatus, WNOHANG);
- if (pc->pipe_shell_pid)
- while (PID_ALIVE(pc->pipe_shell_pid))
- waitpid(pc->pipe_shell_pid,
- &waitstatus, WNOHANG);
+ wait_for_child(&pc->pipe_pid);
+ wait_for_child(&pc->pipe_shell_pid);
if (pc->redirect & (REDIRECT_MULTI_PIPE))
wait_for_children(ALL_CHILDREN);
}
@@ -1967,7 +1954,7 @@
if (CRASHDEBUG(2))
console("pipe: %lx\n", pc->stdpipe);
- return TRUE;;
+ return TRUE;
} else {
close(pc->pipefd[1]); /* child closes write end */
@@ -1998,13 +1985,26 @@
}
}
+static void
+wait_for_child(pid_t *chp)
+{
+ if (*chp != 0)
+ {
+ int waitstatus;
+
+ do ; while (waitpid(*chp, &waitstatus, 0) == -1 && errno == EINTR);
+ *chp = 0;
+ }
+}
+
static void
wait_for_children(ulong waitflag)
{
- int status, pid;
-
while (TRUE) {
- switch (pid = waitpid(-1, &status, WNOHANG))
+ int status;
+ pid_t pid = waitpid(-1, &status, waitflag==ZOMBIES_ONLY? WNOHANG : 0);
+
+ switch (pid)
{
case 0:
if (CRASHDEBUG(2))
@@ -2014,6 +2014,8 @@
break;
case -1:
+ if (errno == EINTR)
+ continue;
if (CRASHDEBUG(2))
console("wait_for_children: no children alive\n");
return;
================ end ================