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Re: ath9k: hwrng blocks for several minutes when phy is un-associated

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Hey again,

On Fri, Jun 24, 2022 at 1:47 AM Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
>
> Hey Gregory,
>
> On Fri, Jun 24, 2022 at 1:36 AM Gregory Erwin <gregerwin256@xxxxxxxxx> wrote:
> >
> > No luck.
> >
> > The first patch caused a warning and oops with ath9k_rng_read() at the
> > top of the call stack when reading from /dev/hwrng:
> >   WARNING: CPU: 1 PID: 454 at kernel/kthread.c:75 kthread_should_stop+0x2a/0x30
> >   BUG: kernel NULL pointer dereference, address: 0000000000000000
> >
> > The second didn't have a noticeable effect, for better or worse.
>
> Alright. That's actually getting us somewhere. So the path in question
> here is from reading /dev/hwrng, not from the kthread that's doing the
> same read.
>
> Can you do a `cat /dev/hwrng > /dev/null`, and then do whatever it is
> you do that causes everything to hang, and then while things are hung
> in the bad way, look at the contents of /proc/[the pid of the cat you
> just ran]/stack?

There's another flow I'm interested in. You said it prevents the
system from sleeping. Does it also make a `ip link set wlan0 down`
hang too? If so, could you send the `/proc/[pid of ip link set
down]/stack ` of a hung ip process? That seems like the more relevant
deadlock to look into.

Jason



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