Re: [PATCH] pstore: Convert buf_lock to semaphore

From: Ard Biesheuvel
Date: Fri Dec 21 2018 - 10:37:24 EST

On Tue, 4 Dec 2018 at 19:06, Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
> On 2018-12-04 09:23:13 [-0800], Kees Cook wrote:
> > Okay, so, if kmsg_dump() uses rcu_read_lock(), that means efi-pstore
> > can _never_ sleep, and it's nothing to do with pstore internals. :( I
> > guess we just hard-code it, then? And efi-pstore should probably only
> > attach to pstore if it has a nonblock implementation (and warn if one
> > isn't available).
> I was about to suggest that. I am not aware if anything else could use
> efi_pstore_write() use that but otherwise you could hardcode it.

efivar_entry_set_safe() will only use the default backend if no
non-blocking variant is provided, in which case it assumes that the
default one is non-blocking. Perhaps we should just assign both
function pointers to the same function in this case.