On Thu, Mar 28, 2024 at 7:55 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
>
> On Thu, Mar 28, 2024 at 5:50 PM Maximilian Luz <luzmaximilian@xxxxxxxxx> wrote:
> >
> > If I understand correctly, it enters an atomic section in
> > qcom_tzmem_alloc() and then tries to schedule somewhere down the line.
> > So this shouldn't be qseecom specific.
> >
> > I should probably also say that I'm currently testing this on a patched
> > v6.8 kernel, so there's a chance that it's my fault. However, as far as
> > I understand, it enters an atomic section in qcom_tzmem_alloc() and then
> > later tries to expand the pool memory with dma_alloc_coherent(). Which
> > AFAIK is allowed to sleep with GFP_KERNEL (and I guess that that's the
> > issue here).
> >
> > I've also tried the shmem allocator option, but that seems to get stuck
> > quite early at boot, before I even have usb-serial access to get any
> > logs. If I can find some more time, I'll try to see if I can get some
> > useful output for that.
> >
>
> Ah, I think it happens here:
>
> + guard(spinlock_irqsave)(&pool->lock);
> +
> +again:
> + vaddr = gen_pool_alloc(pool->genpool, size);
> + if (!vaddr) {
> + if (qcom_tzmem_try_grow_pool(pool, size, gfp))
> + goto again;
>
> We were called with GFP_KERNEL so this is what we pass on to
> qcom_tzmem_try_grow_pool() but we're now holding the spinlock. I need
> to revisit it. Thanks for the catch!
>
> Bart
Can you try the following tree?
https://git.codelinaro.org/bartosz_golaszewski/linux.git
topic/shm-bridge-v10
gen_pool_alloc() and gen_pool_add_virt() can be used without external
serialization. We only really need to protect the list of areas in the
pool when adding a new element. We could possibly even use
list_add_tail_rcu() as it updates the pointers atomically and go
lockless.
Bart
