Date: Tue, 23 Mar 2010 10:00:58 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Dag-Erling =?utf-8?q?Sm=C3=B8rgrav?= <des@des.no>, Dmitry Krivenok <krivenok.dmitry@gmail.com> Subject: Re: Strange behavior of kernel module (output terminated) Message-ID: <201003231000.58961.jhb@freebsd.org> In-Reply-To: <86ocifcmew.fsf@ds4.des.no> References: <da48cf211003230218n56794f0bs27eef860efc0da3e@mail.gmail.com> <86ocifcmew.fsf@ds4.des.no>
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On Tuesday 23 March 2010 7:22:47 am Dag-Erling Sm=C3=B8rgrav wrote:
> Dmitry Krivenok <krivenok.dmitry@gmail.com> writes:
> > /* The function called at load/unload. */
> > static int event_handler(struct module *module, int event, void *arg)
> > {
> > int e =3D 0; /* Error, 0 for normal return status */
> > switch (event)
> > {
> > case MOD_LOAD:
> > uprintf("Hello FreeBSD kernel!\n");
>=20
> I'm not sure it's such a good idea to use uprintf() here. The event
> handler can be called in non-process context.
If you are doing a kldload post-boot it is actually done from some sort of=
=20
process context. We run module handlers synchronously from the kldload(2)=
=20
syscall.
> > int i =3D 0;
> > for(i =3D 0; i < 1000; i++)
> > {
> > uprintf("%3d ", i);
> > if(! (i % 10) ) uprintf("\n");
> > }
>=20
> (i % 10) is not a predicate. The test should be if (i % 10 =3D=3D 0).
>=20
> If you want to work on FreeBSD, I recommend you get used to the
> FreeBSD coding style; see 'man 9 style'.
True, but that doesn't explain the behavior he sees.
> > As you can see the loop was terminated after i=3D=3D466. I tried to
> > load/unload the module many times but the last printed number was
> > always 466.
>=20
> You filled up a buffer somewhere...
Does uprintf() require the caller to flush the output to the tty somehow? =
If=20
so, that seems to be a bug. Nothing in the uprintf(9) manpage suggests tha=
t=20
the output should be manually flushed.
=2D-=20
John Baldwin
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