Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-11 Thread Paul E. McKenney
On Mon, Jan 11, 2021 at 03:42:28PM +0100, Peter Zijlstra wrote: > On Tue, Jan 05, 2021 at 02:01:15PM -0800, Paul E. McKenney wrote: > > Hello! > > > > The RUDE01 rcutorture scenario (and less often, the TASKS01 scenario) > > Is: > > tools/testing/selftests/rcutorture/bin/kvm.sh --duration 10 -

Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-11 Thread Peter Zijlstra
On Tue, Jan 05, 2021 at 02:01:15PM -0800, Paul E. McKenney wrote: > Hello! > > The RUDE01 rcutorture scenario (and less often, the TASKS01 scenario) Is: tools/testing/selftests/rcutorture/bin/kvm.sh --duration 10 --configs RUDE01 --allcpus the right incantation?

Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-06 Thread Paul E. McKenney
On Wed, Jan 06, 2021 at 03:49:46PM +, Valentin Schneider wrote: > On 06/01/21 16:44, Peter Zijlstra wrote: > > On Wed, Jan 06, 2021 at 06:46:21AM -0800, Paul E. McKenney wrote: > >> What would break if I made the code dump out a few entries in the > >> runqueue if the warning triggered? > > > >

Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-06 Thread Valentin Schneider
On 06/01/21 16:44, Peter Zijlstra wrote: > On Wed, Jan 06, 2021 at 06:46:21AM -0800, Paul E. McKenney wrote: >> What would break if I made the code dump out a few entries in the >> runqueue if the warning triggered? > > There was a patch around that did that, Valentin might remember where > that wa

Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-06 Thread Peter Zijlstra
On Wed, Jan 06, 2021 at 06:46:21AM -0800, Paul E. McKenney wrote: > Huh. The WARN does not always generate the lockdep complaint. But > fair enough. Any printk()/WARN/BUG with rq lock held ought to generate that splat, sometimes we die before we splat. The printk rewrite should eventually fix th

Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-06 Thread Paul E. McKenney
On Wed, Jan 06, 2021 at 10:52:14AM +0100, Peter Zijlstra wrote: > On Tue, Jan 05, 2021 at 02:01:15PM -0800, Paul E. McKenney wrote: > > Hello! > > > > The RUDE01 rcutorture scenario (and less often, the TASKS01 scenario) > > results in occasional lockdep splats on v5.11-rc1 on x86. This failure >

Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-06 Thread Peter Zijlstra
On Tue, Jan 05, 2021 at 02:01:15PM -0800, Paul E. McKenney wrote: > Hello! > > The RUDE01 rcutorture scenario (and less often, the TASKS01 scenario) > results in occasional lockdep splats on v5.11-rc1 on x86. This failure > is probabalistic, sometimes happening as much as 30% of the time, but > s

lockdep splat in v5.11-rc1 involving console_sem and rq locks

2021-01-05 Thread Paul E. McKenney
Hello! The RUDE01 rcutorture scenario (and less often, the TASKS01 scenario) results in occasional lockdep splats on v5.11-rc1 on x86. This failure is probabalistic, sometimes happening as much as 30% of the time, but sometimes happening quite a bit less frequently. (And yes, this did result in