On Wed, Sep 26, 2018 at 7:37 PM Eric Biggers [off-list ref] wrote:

Can you please stop accusing Ard of "filibustering" your patchset?  Spending too
long in non-preemptible code is a real problem even on non-RT systems.
syzkaller has been reporting bugs where the kernel spins too long without any
preemption points, both in crypto-related code and elsewhere in the kernel.  So
we've had to add explicit preemption points to address those, as otherwise users
can lock up all CPUs for tens of seconds.  The issue being discussed here is
basically the same except here preemption is being explicitly disabled via
kernel_neon_begin(), so it becomes a problem even on non-CONFIG_PREEMPT kernels.

The async distraction (re:filibustering) and the preempt concern are
two totally different things. I've already posted some code elsewhere
in this thread that addresses the preempt issue that looked good to
Ard. This will be part of v7.