[BusyBox] Bug#212764: 2 race conditions in init implementation
Vladimir N. Oleynik
dzo at simtreas.ru
Mon Oct 6 10:16:46 UTC 2003
>>We blocked, not ignored SIGCHLD. If sigchld raised then signal pending
>>before unblocked. We don`t loses this signal.
> That's true, I was smoking crack here.
?? Idioms? ;-)
> There is still a race here but
> for this reason, see below.
Its point not equivalent for below.
I think, must restore previous verion here.
>>>I have fixed the bug by replacing the wait() call in waitfor() with a
>>>waitpid() call and handle the error.
>>>- 2nd race condition
>>And same point.
> This one is not the same. You unblocked the signal before the second
> fork(). It is not a blocking/unblocking problem here.
> There is a race between the call to signal() and the signal handler
> (child_handler()). If the handler is called before signal(), the code
> will loop forever since waitpid will return -1 with errno == ECHILD.
Ah! You compared with verions have child_handler()? :-0
We remove child handler ~ 15 day ago.
> It is the same for the first race. If the handler is called before
> wait(), wait() will block.
wait MUST block!
> BTW, the SIGCHLD handler reaps all zombies, how can you expect that the
> unchecked calls to wait() and waitpid() will succeed on SMP ?
This code point must have wait(), not waitpid()
>>I recomended restore previous version from CVS before realy
> I recommend you leave it in the CVS.
You have found problems in yours patch for this letter!
> Testing return codes is good
This code is difficult for testing for correctness.
Previous code may be have problem, I look Jean have point for demonstrate.
But your patch is bad!
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