On Tue, Feb 23, 2021 at 02:53:40PM +0100, Juri Lelli wrote: > On 23/02/21 12:00, Sebastian Andrzej Siewior wrote: > > On 2021-02-23 11:49:07 [+0100], Juri Lelli wrote: > > > Hi, > > Hi, > > > > > I'm seeing the following splat right after boot (or during late boot > > > phases) with v5.11-rt7 (LOCKDEP enabled). > > … > > > [ 85.273588] WARNING: CPU: 5 PID: 1416 at include/linux/seqlock.h:271 > > > nft_counter_eval+0x95/0x130 [nft_counter] > > … > > > [ 85.273713] RIP: 0010:nft_counter_eval+0x95/0x130 [nft_counter] > > > > This is a per-CPU seqcount_t in net/netfilter/nft_counter.c which is > > only protected by local_bh_disabled(). The warning expects preemption > > to be disabled which is the case on !RT but not on RT. > > > > Not sure what to do about this. It is doing anything wrong as of now. It > > is noisy. > > So, I'm a bit confused and I'm very likely missing details (still > digesting the seqprop_ magic), but write_seqcount_being() has > > if (seqprop_preemptible(s)) > preempt_disable(); > > which in this case (no lock associated) is defined to return false,
Preemption is disabled if and only if: 1. It's a CONFIG_PREEMPT_RT=n system 2. There's a lock associated with the sequence counter 3. That lock is also preemptible (e.g., a mutex) In your case, the 3 condititions are OFF. You're on a PREEMPT_RT=y kernel and the sequence counter in question has no lock associated. As Sebastian summarized, the error is just "noisy" at this point. We will of course need to find a (mainline-friendly) way to let the lockdep splat go away for -rt kernels. But for now, it's not harmful. Good luck, -- Ahmed S. Darwish
