Re: [BUG] Splat during modest hazptrtorture run

[Bradley Morgan]

On 7 October 2026 16:59:36 BST, "Paul E. McKenney" <paulmck@xxxxxxxxxx>
wrote:
>On Wed, Oct 07, 2026 at 03:09:27AM -0400, Mathieu Desnoyers wrote:
>> On 2026-10-06 19:40, Paul E. McKenney wrote:
>> > Hello!
>> > 
>> > This is all new code, so the bug could be anywhere.  So you all need
>> > to know.  ;-)
>> > 
>> > I got this from the NOPREEMPT variant of hazptr during a nominal
>> > "--duration 60" run of torture.sh on x86 with the guest OS split
>across
>> > two NUMA nodes:
>> > 
>> > [  137.765104] WARNING: kernel/rcu/hazptrtorture.c:658 at
>hazptr_torture_stats_print+0x25b/0x4f0, CPU#1: hazptr_torture_/136
>> > [  137.768647] Modules linked in:
>> > [  137.768891] CPU: 1 UID: 0 PID: 136 Comm: hazptr_torture_ Not
>tainted 7.3.0-rc5-00661-ga1f1e4890d1d-dirty #193 PREEMPTLAZY
>> > [  137.769683] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
>BIOS 1.16.3-6.el9 11/05/2023
>> > [  137.770319] RIP: 0010:hazptr_torture_stats_print+0x25b/0x4f0
>> > [  137.770735] Code: 48 83 c4 20 e8 86 44 fe ff 41 83 fd 01 7e 23 48
>c7 c6 6e 85 17 b0 48 c7 c7 db 27 17 b0 e8 6d 44 fe ff f0 ff 05 76 6e 0a 02
>90 <0f> 0b 90 4c 8b 64 24 70 48 c7 c7 73 85 17 b0 e8 51 44 fe ff 48 8b
>> > [  137.772061] RSP: 0018:ffffa738004ffdf0 EFLAGS: 00010202
>> > [  137.772435] RAX: 0000000000000004 RBX: ffffa738004ffe08 RCX:
>0000000000000027
>> > [  137.772950] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
>0000000000000001
>> > [  137.773455] RBP: ffffa738004ffe60 R08: 4000000000001236 R09:
>ffffffffb01727df
>> > [  137.773980] R10: 0000000020212121 R11: 0000000020212121 R12:
>0000000000000000
>> > [  137.774479] R13: 0000000000000002 R14: 000000000002ffd6 R15:
>0000000000034f03
>> > [  137.775000] FS:  0000000000000000(0000) GS:ffff999c2e502000(0000)
>knlGS:0000000000000000
>> > [  137.775578] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> > [  137.776001] CR2: 0000000000000000 CR3: 0000000008830000 CR4:
>00000000000006f0
>> > [  137.776512] Call Trace:
>> > [  137.776700]  <TASK>
>> > [  137.776863]  ? __pfx_hazptr_torture_stats+0x10/0x10
>> > [  137.777207]  hazptr_torture_stats+0x25/0x70
>> > [  137.777508]  kthread+0xd9/0x110
>> > [  137.777751]  ? __pfx_kthread+0x10/0x10
>> > [  137.778017]  ret_from_fork+0x1bd/0x220
>> > [  137.778285]  ? __pfx_kthread+0x10/0x10
>> > [  137.778560]  ret_from_fork_asm+0x1a/0x30
>> > [  137.778849]  </TASK>
>> > [  137.779007] ---[ end trace 0000000000000000 ]---
>> > 
>> > I have not yet seen this during a PREEMPT run.  Line 658 of
>> > hazptrtorture.c is the WARN_ON_ONCE() below:
>> > 
>> > 	if (i > 1) {
>> > 		pr_cont("%s", "!!! ");
>> > 		atomic_inc(&n_hazptr_torture_error);
>> > 		WARN_ON_ONCE(i > 1); // Too-short grace period
>> > 	}
>> > 
>> > Any thoughts on what might be causing this?
>> 
>> Hi Paul!
>> 
>> Can you share which tree and branch (commit) this is running ?
>> 
>> Does it include my fix from this series ? That would be patch 1 of:
>> 
>>
>https://lore.kernel.org/lkml/20260927155134.4740-1-mathieu.desnoyers@xxxxxxxxxxxx/
>
>Ah, no, I somehow got the impression that this series was going to be
>updated, so did not apply it.  Apologies!
>
>I will pull these in.
>
>> Does it run the additional series from Kunwu Chan found at
>>
>https://lore.kernel.org/lkml/20261002170847.3653663-1-kunwu.chan@xxxxxxxxx/
>?
>
>No, but if you are good with it I will pull it in.
>
>May I add your Acked-by or Reviewed-by?

Sorry to impede but I'd be fine with it going in, I'll add my A-B for this:

Acked-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>


>
>							Thanx, Paul
>
>> Thanks,
>> 
>> Mathieu
>> 
>> > 
>> > For that matter, can anyone else reproduce this?
>> > 
>> > 								Thanx, Paul
>> 
>> 
>> -- 
>> Mathieu Desnoyers
>> EfficiOS Inc.
>> https://www.efficios.com

--- Thanks!
"I'm not a very positive person" - Linus torvalds