Date: Sun, 13 Dec 1998 22:53:54 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: archie@whistle.com (Archie Cobbs) Cc: peter.edwards@isocor.ie, dillon@apollo.backplane.com, jwd@unx.sas.com, freebsd-current@FreeBSD.ORG Subject: Re: inetd: realloc/free bug Message-ID: <199812132253.PAA10799@usr09.primenet.com> In-Reply-To: <199812111940.LAA27652@bubba.whistle.com> from "Archie Cobbs" at Dec 11, 98 11:40:58 am
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> I guess I was thinking in terms of the event library model; that is,
> you don't handle the signal event in the signal handler (because in
> general the event handler could call malloc(), etc), but rather you
> simply set a flag (call it "signalFlag").
>
> The race condition is getting a signal between the first and second
> lines below:
>
> sigprocmask(SIG_UNBLOCK ..) /* unblock signals */
> r = select(...) /* wait for event */
> sigprocmask(SIG_BLOCK ..) /* block signals */
>
> if (signalFlag || r > 0) {
> ... /* handle event(s) */
> }
>
> But there are probably smarter ways to do it than this.
Yes. Don't block signals, use a setjmp for the select, and choose
system call restart behaviour.
The race you are concerned with is a signal occurring before the
select starts, and the resulting EINTR.
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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