On Wed, Dec 06, 2017 at 11:31:30PM +0900, Namhyung Kim wrote: > > There's also a race against put_callchain_buffers() there, consider: > > > > > > get_callchain_buffers() put_callchain_buffers() > > mutex_lock(); > > inc() > > dec_and_test() // false > > > > dec() // 0 > > > > > > And the buffers leak. > > Hmm.. did you mean that get_callchain_buffers() returns an error?
Yes, get_callchain_buffers() fails, but while doing so it has a temporary increment on the count. > AFAICS it cannot fail when it sees count > 1 (and callchain_cpus_ > entries is allocated). It can with your patch. We only test event_max_stack against the sysctl after incrementing.
