glebfm/strace
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

detach(): warn if we see ECHILD from waitpid

Browse Source 
* strace.c (detach): Warn if we see ECHILD from waitpid.
Explain in comments that we don't normally expect !WIFSTOPPED
either, and also that PTRACE_CONT failure isn't expected
(the "break" there is a "I'm confused, bailing out" code style)..

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko 2013-06-20 12:10:21 +02:00
parent 4a9ba989e6
commit fdfa47af7e
1 changed files with 23 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
strace.c
View File

@ -764,7 +764,7 @@ detach(struct tcb *tcp)
}
else if (errno != ESRCH) {
/* Shouldn't happen. */
perror_msg("detach: ptrace(%u,PTRACE_DETACH)", tcp->pid);
perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
}
else
/* ESRCH: process is either not stopped or doesn't exist. */
@ -789,7 +789,7 @@ detach(struct tcb *tcp)
if (!error)
interrupt_done = 1;
else if (errno != ESRCH)
perror_msg("detach: ptrace(%u,PTRACE_INTERRUPT)", tcp->pid);
perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
}
else {
error = my_tkill(tcp->pid, SIGSTOP);
@ -807,13 +807,25 @@ detach(struct tcb *tcp)
if (waitpid(tcp->pid, &status, __WALL) < 0) {
if (errno == EINTR)
continue;
if (errno == ECHILD) /* Already gone. */
break;
/*
* if (errno == ECHILD) break;
* ^^^ WRONG! We expect this PID to exist,
* and want to emit a message otherwise:
*/
perror_msg("detach: waitpid(%u)", tcp->pid);
break;
}
if (!WIFSTOPPED(status)) {
/* Au revoir, mon ami. */
/*
* Tracee exited or was killed by signal.
* We shouldn't normally reach this place:
* we don't want to consume exit status.
* Consider "strace -p PID" being ^C-ed:
* we want merely to detach from PID.
*
* However, we _can_ end up here if tracee
* was SIGKILLed.
*/
break;
}
sig = WSTOPSIG(status);
@ -859,8 +871,13 @@ detach(struct tcb *tcp)
sig = 0;
/* Can't detach just yet, may need to wait for SIGSTOP */
error = ptrace_restart(PTRACE_CONT, tcp, sig);
if (error < 0)
if (error < 0) {
/* Should not happen.
* Note: ptrace_restart returns 0 on ESRCH, so it's not it.
* ptrace_restart already emitted error message.
*/
break;
}
}
}