Messages in this thread | | | Date | Wed, 21 Feb 2007 09:42:25 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] fix handling of SIGCHILD from reaped child |
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On Tue, 20 Feb 2007 20:20:49 +0300 Oleg Nesterov <oleg@tv-sign.ru> wrote: > > > > + clear_stale_sigchild(current, retval); > > > > > > But we are not checking that SIGCHLD is blocked? > > > > > I'm sorry if I don't read SUSv3 correctly. SUSv3 doesn't define how we should > > do if SIGCHLD is not blocked.(so I don't check not-blocked case.) > > Probably it is me who misunderstands SUSv3. Could you point me the reference > to authoritative document? My understanding: if blocked AND wait() succeeds. > I read this: http://www.opengroup.org/onlinepubs/009695399/
> > IMHO, user's sig-child-handler is tend to call wait()/waitpid() and expects > > successful return. So removing stale signal here may be good. > > Yes. But sig-child-handler should do > > while (wait() >= 0) > .... > > anyway, because SIGCHLD is not a realtime signal. >
Ah...it looks I should explation why I found this more.
A user (who is migrated from Solaris) met following situation. ==(single threaded program.)
pid1 = fork(); if (!pid1) { do_something_forever(); } ....set SIGCHLD handler here to catch pid1's error-exit....
if (!pid2) { do_something_in_shortterm(); } Block SIGCHLD ret = waitpid(pid2, hoge, hoge); // wait for pid2 UNBlock SIGCHLD ==
And SIGCHLD handler didn't use WNOHANG. I asked him to fix his program. He agreed.(So, no problem now.)
While our problem was fixed, it seems Linux doesn't meet spec.(SUSv3) So I posted. But this is rare situation and this fix makes codes ugly....
Thanks, -Kame
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