Date: Sat, 28 Aug 2010 00:38:27 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r211896 - head/sbin/hastd Message-ID: <20100827213827.GD2396@deviant.kiev.zoral.com.ua> In-Reply-To: <201008272049.o7RKn63o007138@svn.freebsd.org> References: <201008272049.o7RKn63o007138@svn.freebsd.org>
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[-- Attachment #1 --] On Fri, Aug 27, 2010 at 08:49:06PM +0000, Pawel Jakub Dawidek wrote: > Author: pjd > Date: Fri Aug 27 20:49:06 2010 > New Revision: 211896 > URL: http://svn.freebsd.org/changeset/base/211896 > > Log: > Check if no signals were delivered just before going to sleep. > > MFC after: 2 weeks > Obtained from: Wheel Systems Sp. z o.o. http://www.wheelsystems.com > > Modified: > head/sbin/hastd/primary.c > > Modified: head/sbin/hastd/primary.c > ============================================================================== > --- head/sbin/hastd/primary.c Fri Aug 27 20:48:12 2010 (r211895) > +++ head/sbin/hastd/primary.c Fri Aug 27 20:49:06 2010 (r211896) > @@ -1988,7 +1988,9 @@ guard_thread(void *arg) > rw_unlock(&hio_remote_lock[ii]); > } > } > - (void)cv_timedwait(&hio_guard_cond, &hio_guard_lock, timeout); > + /* Sleep only if a signal wasn't delivered in the meantime. */ > + if (!sigexit_received && !sighup_received && !sigchld_received) > + cv_timedwait(&hio_guard_cond, &hio_guard_lock, timeout); > mtx_unlock(&hio_guard_lock); > } > /* NOTREACHED */ I wanted to say that this is racy, because if a signal is delivered after the check is done but before the sleep, you loose. After looking at the signal handler, I noted that you call not async-safe functions in the handler. This is easy way to get undefined behaviour, i.e. probably crash. And wakeup from the handler would have the same race as sigXXX_received check. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkx4MFMACgkQC3+MBN1Mb4jynwCffUXFzlOu83zhUyVCrxI8POfT rIEAniRX+OPh21oUBgrZyes/YzqrMZcL =n2kn -----END PGP SIGNATURE-----help
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