On Wed, Apr 14, 2021 at 08:39:04PM +0200, Toke Høiland-Jørgensen wrote: > "Paul E. McKenney" <paulmck@xxxxxxxxxx> writes: > > > On Wed, Apr 14, 2021 at 10:59:23AM -0700, Alexei Starovoitov wrote: > >> On Wed, Apr 14, 2021 at 10:52 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > >> > > >> > > > > > if (num_online_cpus() > 1) > >> > > > > > synchronize_rcu(); > >> > > >> > In CONFIG_PREEMPT_NONE=y and CONFIG_PREEMPT_VOLUNTARY=y kernels, this > >> > synchronize_rcu() will be a no-op anyway due to there only being the > >> > one CPU. Or are these failures all happening in CONFIG_PREEMPT=y kernels, > >> > and in tests where preemption could result in the observed failures? > >> > > >> > Could you please send your .config file, or at least the relevant portions > >> > of it? > >> > >> That's my understanding as well. I assumed Toke has preempt=y. > >> Otherwise the whole thing needs to be root caused properly. > > > > Given that there is only a single CPU, I am still confused about what > > the tests are expecting the membarrier() system call to do for them. > > It's basically a proxy for waiting until the objects are freed on the > kernel side, as far as I understand... There are in-kernel objects that are freed via call_rcu(), and the idea is to wait until these objects really are freed? Or am I still missing out on what is going on? Thanx, Paul
