On Wed, 7 Jun 2017, Vlastimil Babka wrote: > >> Hmm I'd expect such spin lock to be reported together with mmap_sem in > >> the debugging "locks held" message? > > > > My bisection of the problem is about half done. My latest good version is > > commit > > 7b8cd33 and the latest bad one is 2ea659a. Only about 7 steps to go. > > Hmm, your bisection will most likely just find commit 338a16ba15495 > which added the cond_resched() at mm/khugepaged.c:655. CCing David who > added it. >
I agree it's probably going to bisect to 338a16ba15495 since it's the cond_resched() at the line number reported, but I think there must be something else going on. I think the list of locks held by khugepaged is correct because it matches with the implementation. The preempt_count(), as suggested by Andrew, does not. If this is reproducible, I'd like to know what preempt_count() is.
