On Wed, 5 Aug 2020 19:56:21 -0700 Chris Goldsworthy <cgoldswo@xxxxxxxxxxxxxx> wrote: > On mobile devices, failure to allocate from a CMA area constitutes a > functional failure. Sometimes during CMA allocations, we have observed > that pages in a CMA area allocated through alloc_pages(), that we're trying > to migrate away to make room for a CMA allocation, are temporarily pinned. > This temporary pinning can occur when a process that owns the pinned page > is being forked (the example is explained further in the commit text). > This patch addresses this issue by adding a sleep-and-retry loop in > cma_alloc() . There's another example we know of similar to the above that > occurs during exit_mmap() (in zap_pte_range() specifically), but I need to > determine if this is still relevant today. Sounds fairly serious but boy, we're late for 5.9. I can queue it for 5.10 with a cc:stable so that it gets backported into earlier kernels a couple of months from now, if we think the seriousness justifies backporting(?). Or I can do something else - thoughts? And... it really is a sad little patch, isn't it? Instead of fixing the problem, it reduces the problem's probability by 5x. Can't we do better than this?
