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? -- Michal Hocko SUSE Labs
