Date: Thu, 10 Aug 2006 10:23:59 -0500 From: Brooks Davis <brooks@one-eyed-alien.net> To: Divacky Roman <xdivac02@stud.fit.vutbr.cz> Cc: hackers@freebsd.org Subject: Re: SoC: help with LISTs and killing procs Message-ID: <20060810152359.GA21318@lor.one-eyed-alien.net> In-Reply-To: <20060810151616.GA17109@stud.fit.vutbr.cz> References: <20060810151616.GA17109@stud.fit.vutbr.cz>
next in thread | previous in thread | raw e-mail | index | archive | help
--cNdxnHkX5QqsyA0e
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
On Thu, Aug 10, 2006 at 05:16:17PM +0200, Divacky Roman wrote:
> hi
>=20
> I am doing this:
>=20
> (pseudocode)
> LIST_FOREACH_SAFE(em, &td_em->shared->threads, threads, tmp_em) {
>=20
> kill(em, SIGKILL);
> }
>=20
> kill(SIGKILL) calls exit() which calls my exit_hook()
>=20
> my exit_hook() does LIST_REMOVE(em, threads).
>=20
> the problem is that this is not synchronous so I am getting a panic by IN=
VARIANTS
> that "Bad link elm prev->next !=3D elm". This is because I list 1st item =
in the list
> I call kill on it, then process 2nd list, then scheduler preempts my code=
and calls
> exit() on the first proc which removes the first entry and bad things hap=
pen.=20
>=20
> I see this possible solutions:
>=20
> make this synchronous, it can be done by something like:
>=20
> ....
> kill(em, SIGKILL);
> wait_for_proc_to_vanish();
>=20
> pls. tell me what do you think about this solution and if its correct wha=
t is the wait_for_proc_to_vanish()
>=20
> maybe there's some better solution, pls tell me.
It sounds like you need a lock protecting the list. If you held it over
the whole loop you could signal all processes before the exit_hook could
remove any.
-- Brooks
--cNdxnHkX5QqsyA0e
Content-Type: application/pgp-signature
Content-Disposition: inline
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.2 (FreeBSD)
iD8DBQFE20+OXY6L6fI4GtQRArGnAJ9bYoA/FKM2i/nC9ruQOgf0eBqVeACggCp3
LYDzzW882nN0kTqY59TqoqI=
=wWhk
-----END PGP SIGNATURE-----
--cNdxnHkX5QqsyA0e--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20060810152359.GA21318>