Date: Fri, 20 Oct 2006 14:34:53 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: usleepless@gmail.com Cc: freebsd-hackers@freebsd.org Subject: Re: Fwd: Removing Giant from a driver Message-ID: <20061020213453.GR23971@funkthat.com> In-Reply-To: <c39ec84c0610150204h6110e7ffr4716ec5641f11aca@mail.gmail.com> References: <c39ec84c0610141332q7abf9220q8b2715f33a72e58b@mail.gmail.com> <c39ec84c0610150204h6110e7ffr4716ec5641f11aca@mail.gmail.com>
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usleepless@gmail.com wrote this message on Sun, Oct 15, 2006 at 11:04 +0200:
> i have been tweaking the pvr250 driver to support pvr150s/500s. now i
> want to remove Giant from the code.
>
> problem is, i am not sure what to do. i have created a mutex which
> replaces the spltty and splx calls. but this crashes my box :-)
>
> the original code looks like this:
> /*
> * Allocate a DMA tag for the scatter / gather list.
> */
> error = bus_dma_tag_create(sc->parent_dmat, 1, 0,
> BUS_SPACE_MAXADDR_32BIT,
> BUS_SPACE_MAXADDR, NULL, NULL,
> CXM_SG_BUFFERS
> * sizeof(struct cxm_sg_entry), 1,
> BUS_SPACE_MAXSIZE_32BIT, 0,
> #if __FreeBSD_version >= 501102
> busdma_lock_mutex, &Giant,
> #endif
> &sc->enc_sg.dmat);
>
> what should it look like?
You should be creating a mutex (using mtx_init) at attach time, and
pass that mutex instead of Giant...
> and how will i prevent the interrupt routine from interfering with
> userland operations? can i place a "mtx_lock()" call in the interrupt
> routine?
Correct.... Fast interrupt handlers cannot use a sleeping mutex, but
I doubt this driver is using a fast interrupt handler...
> is there a howto somewhere?
There are man pages on how to use the various locking primitives, but
it is assumed that you have knowlege of concurrent programming... You
can take a look at books on pthreads and other related matierals for
info on using locks...
If you figure out the licensing issues w/ the firmware, I'll import
the driver into FreeBSD...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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