Am 24.08.2018 um 15:24 schrieb Michal Hocko: > On Fri 24-08-18 15:10:08, Christian König wrote: >> Am 24.08.2018 um 15:01 schrieb Michal Hocko: >>> On Fri 24-08-18 14:52:26, Christian König wrote: >>>> Am 24.08.2018 um 14:33 schrieb Michal Hocko: >>> [...] >>>>> Thiking about it some more, I can imagine that a notifier callback which >>>>> performs an allocation might trigger a memory reclaim and that in turn >>>>> might trigger a notifier to be invoked and recurse. But notifier >>>>> shouldn't really allocate memory. They are called from deep MM code >>>>> paths and this would be extremely deadlock prone. Maybe Jerome can come >>>>> up some more realistic scenario. If not then I would propose to simplify >>>>> the locking here. We have lockdep to catch self deadlocks and it is >>>>> always better to handle a specific issue rather than having a code >>>>> without a clear indication how it can recurse. >>>> Well I agree that we should probably fix that, but I have some concerns to >>>> remove the existing workaround. >>>> >>>> See we added that to get rid of a real problem in a customer environment and >>>> I don't want to that to show up again. >>> It would really help to know more about that case and fix it properly >>> rather than workaround it like this. Anyway, let me think how to handle >>> the non-blocking notifier invocation then. I was not able to come up >>> with anything remotely sane yet. >> With avoiding allocating memory in the write lock path I don't see an issue >> any more with that. >> >> All what the write lock path does now is adding items to a linked lists, >> arrays etc.... > Can we change it to non-sleepable lock then? No, the write side doesn't sleep any more, but the read side does. See amdgpu_mn_invalidate_node() and that is where you actually need to handle the non-blocking flag correctly. Christian.
