Re: [RFC PATCH] mm/slub: fix a deadlock due to incomplete patching of cpusets_enabled()

[Christopher Lameter]

On Wed, 26 Jul 2017, Dima Zavin wrote:

> The fix is to cache the value that's returned by cpusets_enabled() at the
> top of the loop, and only operate on the seqlock (both begin and retry) if
> it was true.

I think the proper fix would be to ensure that the calls to
read_mems_allowed_{begin,retry} cannot cause the deadlock. Otherwise you
have to fix this in multiple places.

Maybe read_mems_allowed_* can do some form of synchronization or *_retry
can implictly rely on the results of cpusets_enabled() by *_begin?