Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Oct 13, 2022 at 03:14:08PM +1000, Nicholas Piggin wrote:
> > > 
> > > BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
> > > caller is .__flush_tlb_pending+0x40/0xf0
> > > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.0.0-28380-gde492c83cae0-dirty #4
> > > Hardware name: PowerMac3,1 PPC970FX 0x3c0301 PowerMac
> > > Call Trace:
> > > [c0000000044c3540] [c000000000f93ef0] .dump_stack_lvl+0x7c/0xc4 (unreliable)
> > > [c0000000044c35d0] [c000000000fc9550] .check_preemption_disabled+0x140/0x150
> > > [c0000000044c3660] [c000000000073dd0] .__flush_tlb_pending+0x40/0xf0
> > > [c0000000044c36f0] [c000000000334434] .__apply_to_page_range+0x764/0xa30
> > > [c0000000044c3840] [c00000000006cad0] .change_memory_attr+0xf0/0x160
> > > [c0000000044c38d0] [c0000000002a1d70] .bpf_prog_select_runtime+0x150/0x230
> > > [c0000000044c3970] [c000000000d405d4] .bpf_prepare_filter+0x504/0x6f0
> > > [c0000000044c3a30] [c000000000d4085c] .bpf_prog_create+0x9c/0x140
> > > [c0000000044c3ac0] [c000000002051d9c] .ptp_classifier_init+0x44/0x78
> > > [c0000000044c3b50] [c000000002050f3c] .sock_init+0xe0/0x100
> > > [c0000000044c3bd0] [c000000000010bd4] .do_one_initcall+0xa4/0x438
> > > [c0000000044c3cc0] [c000000002005008] .kernel_init_freeable+0x378/0x428
> > > [c0000000044c3da0] [c0000000000113d8] .kernel_init+0x28/0x1a0
> > > [c0000000044c3e10] [c00000000000ca3c] .ret_from_kernel_thread+0x58/0x60
> > > 
> > > This in turn is because __flush_tlb_pending() calls:
> > > 
> > > static inline int mm_is_thread_local(struct mm_struct *mm)
> > > {
> > >          return cpumask_equal(mm_cpumask(mm),
> > >                                cpumask_of(smp_processor_id()));
> > > }
> > > 
> > > __flush_tlb_pending() has a comment about this:
> > > 
> > >   * Must be called from within some kind of spinlock/non-preempt region...
> > >   */
> > > void __flush_tlb_pending(struct ppc64_tlb_batch *batch)
> > > 
> > > So I guess that didn't happen for some reason? Maybe this is indicative
> > > of some lock imbalance that then gets hit later?
> >
> > I managed to bisect that problem. Unfortunately it points to the
> > scheduler merge. No idea what to do about that. Any idea ?
> > I am copying Peter and Ingo for comments.
> >
> 
> > # first bad commit: [30c999937f69abf935b0228b8411713737377d9e] Merge tag 'sched-core-2022-10-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
> 
> This might be a red herring because I can reproduce without it.
> I think we can fix this with some preempt critical sections, they
> don't look too much of a problem.
> 

Do you refer to the bisect of the BUG: message above, or to the other
problem ? I can try to repeat the bisect with some retries if you
think that 30c999937f69a isn't responsible for "BUG: using
smp_processor_id() in preemptible [00000000] code".

Thanks,
Guenter