On Thu, Nov 26, 2009 at 06:25:24PM +0100, Oleg Nesterov wrote:
> On 11/26, Oleg Nesterov wrote:
> >
> > On 11/26, Ananth N Mavinakayanahalli wrote:
> > >
> > > step-fork: step-fork.c:56: handler_fail: Assertion `0' failed.
> > > /bin/sh: line 5: 17325 Aborted ${dir}$tst
> > > FAIL: step-fork
> >
> > Good to know, thanks again Ananth.
> >
> > I'll take a look. Since I know nothing about powerpc, I can't
> > promise the quick fix ;)
> >
> > The bug was found by code inspection, but the fix is not trivial
> > because it depends on arch/, and it turns out the arch-independent
> > fix in
> >
> > ptrace-copy_process-should-disable-stepping.patch
> > http://marc.info/?l=linux-mm-commits&m=125789789322573
> >
> > doesn't work.
>
> Just noticed the test-case fails in handler_fail(). Most probably
> this means it is killed by SIGALRM because either parent or child
> hang in wait(). Perhaps we have another (ppc specific?) bug, but
> currently I do not understand how this is possible, this should
> not be arch-dependent.
I can confirm that we have another bug on ppc arch. The test case below
is spinning forever,
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <assert.h>
int main(void)
{
int pid, status;
if (!(pid = fork())) {
assert(ptrace(PTRACE_TRACEME) == 0);
kill(getpid(), SIGSTOP);
if (!fork())
return 0;
printf("fork passed..\n");
return 0;
}
for (;;) {
assert(pid == wait(&status));
if (WIFEXITED(status))
break;
assert(ptrace(PTRACE_SINGLESTEP, pid, 0,0) == 0);
}
printf("Parent exit.\n");
return 0;
}
it doesn't hang, the parent is spinning around for, the test case
isn't printing anything. Seems like fork() can't complete under
PTRACE_SINGLESTEP.
--
Veaceslav
