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SubjectRe: [GIT PULL]: firmware patches for building firmware into kernel
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On Fri, 2008-08-08 at 09:01 +0530, Jaswinder Singh wrote:
> On Thu, 2008-08-07 at 14:21 -0400, David Dillow wrote:
> > I just looked at the tree; it still has locking issues, and needs
> > further review. You must protect the list from modification while you
> > iterate it looking for an match on the requested firmware.
>
> So here is updated patch:

I'll take a closer look when I'm awake, but there are some nitpicky
style issues remaining:

> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 6074321..71ec20d 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c

> @@ -568,19 +569,22 @@ void release_firmware(const struct firmware *fw)
> {
> struct firmware_list *flst;
>
> + mutex_lock(&fw_lock);
> if (fw)
> list_for_each_entry(flst, &firmwarelist, list)
> if (fw == flst->fw) {
> printk(KERN_INFO
> "firmware: releasing %s count %d\n",
> flst->name, flst->count);
> - mutex_lock(&fw_lock);
> flst->count--;
> - mutex_unlock(&fw_lock);
> - if (flst->count == 0)
> - __release_firmware(fw, flst);
> - return;
> + if (flst->count == 0) {
> + mutex_unlock(&fw_lock);
> + return __release_firmware(fw, flst);
> + }
> + goto out;
> }
> +out:
> + mutex_unlock(&fw_lock);
> }

You don't need the 'goto out', a break will work fine. And you'll not be
pressed up against the right side of the screen if you just do
if (!fw)
return;
at the top of the function.

> @@ -598,6 +602,7 @@ void release_firmware_all(const struct firmware *fw)

I still don't like this exception to the get/put ref-counting. Is this
used anywhere else in your series, or was typhoon the only one?

> > Also, was it legal to call release_firmware() from an atomic context? It can now
> > sleep, which may be an issue...
>
> yes, release_firmware can sleep.
> So now release_firmware also joined the family of request_firmware.

The question wasn't if it can sleep now, it was if it could sleep before
you started changing it. I now know that it has always called vfree(),
so it has always needed to be able to sleep.

> Any how release_firmware will be called below request_firmware or during
> exit, I do not think this will make any issue.

I need to run down code to see if my thoughts are realistic, but say
eth0 was a typhoon:

modprobe typhoon
ip link set eth0 up
rmmod typhoon
<firmware unloaded>
<sleep in typhoon_remove_one() waiting for 'ip link set eth0 down'>
<Tx timeout, needing to reset and reload firmware>
Boom.
Dave



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