Hello, On Thu, Dec 27, 2018 at 05:36:47PM -0800, Linus Torvalds wrote: > > Unless I'm totally confused, which is definitely possible, I don't > > think there's a race condition and the only bug is the > > tmp_alone_branch pointer getting dangled, which maybe doesn't happen > > all that much? > > Ahh. That would explain the list corruption. The next > list_add_leaf_cfs_rq() could try to add to a removed entry. > > How would you reset it? Do something like > > rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; > > for every removal, or make it conditional on it matching the removed entry?
Vincent knows that part way better than me but I think the safest way would be doing the optimization removal iff tmp_alone_branch is already pointing to leaf_cfs_rq_list. IIUC, it's pointing to something else only while a branch is being built and deferring optimization removal by an avg update cycle isn't gonna make any difference anyway. Thanks. -- tejun
