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Date:   Sun, 23 Jul 2023 00:26:58 +0000
From:   Joel Fernandes <joel@joelfernandes.org>
To:     Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        torvalds@linux-foundation.org, stable@vger.kernel.org, lwn@lwn.net,
        jslaby@suse.cz, rcu@vger.kernel.org
Subject: Re: [BUG] Re: Linux 6.4.4
Message-ID: <20230723002658.GB284241@google.com>
References: <2023071940-suspect-ominous-4a6a@gregkh>
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On Sat, Jul 22, 2023 at 09:00:16AM +0800, Zhouyi Zhou wrote:
> On Fri, Jul 21, 2023 at 9:51 AM Zhouyi Zhou <zhouzhouyi@gmail.com> wrote:
> >
> > On Thu, Jul 20, 2023 at 9:31 PM Joel Fernandes <joel@joelfernandes.org> wrote:
> > >
> > > On Wed, Jul 19, 2023 at 05:06:39PM +0200, Greg Kroah-Hartman wrote:
> > > > I'm announcing the release of the 6.4.4 kernel.
> > > >
> > > > All users of the 6.4 kernel series must upgrade.
> > > >
> > > > The updated 6.4.y git tree can be found at:
> > > >       git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-6.4.y
> > > > and can be browsed at the normal kernel.org git web browser:
> > > >       https://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git;a=summary
> > >
> > > I have been consistently hitting the following splat with rcutorture's TREE03
> > > test on 6.4.4. This happened with 6.4.4-rc3 as well.
> > Hi, I am also interested in this topic , I am going to test 6.4.4 on my laptop
> I rcu tortured 6.4.4 on my Intel(R) Core(TM) i7-11800H laptop for 2
> rounds each of which lasting 7 hours.
> all of them report:
> Summary: Successes: 55 Failures: 0.

Thanks for checking. One thing about my environment is it is nested
virtualized. So rcutorture is actually running inside a second-level of
virtualization which probably adds a lot of timing related uncertainty to my
testing (which could be a good thing :P).

thanks,

 - Joel


> 
> Thanks, Zhouyi
> >
> > Thanks, Zhouyi
> > >
> > > Happens at:
> > >                 WARN_ON_ONCE(n_rcu_torture_boost_failure); // boost failed (TIMER_SOFTIRQ RT prio?)
> > >
> > > So likely RCU boosting is failing:
> > >
> > > The full TREE03 splat:
> > > [   54.243588] ------------[ cut here ]------------
> > > [   54.244547] rcu-torture: rcu_torture_boost started
> > > [   54.247643] WARNING: CPU: 12 PID: 166 at kernel/rcu/rcutorture.c:2227 rcu_torture_stats_print+0x5b2/0x620
> > > [   54.273082] Modules linked in:
> > > [   54.278336] CPU: 12 PID: 166 Comm: rcu_torture_sta Not tainted 6.4.4-g62813c2d2a36 #1
> > > [   54.288540] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > [   54.300499] RIP: 0010:rcu_torture_stats_print+0x5b2/0x620
> > > [   54.307525] Code: 00 00 48 8b 05 3f 6c 46 02 e9 4a fe ff ff 0f 0b e9 02 fd ff ff 0f 0b e9 09 fd ff ff 0f 0b e9 10 fd ff ff 0f 0b e9 17 fd ff ff <0f> 0b e9 1e fd ff ff 0f 0b e9 21 fd ff ff e8 0b 54 ff ff 84 c0 0f
> > > [   54.331276] RSP: 0000:ffff9fef805efe08 EFLAGS: 00010202
> > > [   54.338374] RAX: 0000000000000000 RBX: ffff9fef805efe88 RCX: 00000000ffffdfff
> > > [   54.347738] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
> > > [   54.358923] RBP: ffff9fef805efe30 R08: 00000000ffffdfff R09: 00000000ffffdfff
> > > [   54.368209] R10: ffffffff94e59280 R11: ffffffff94e59280 R12: 0000000000000001
> > > [   54.377367] R13: 0000000000000000 R14: 00000000000002fc R15: ffffffff93514000
> > > [   54.386739] FS:  0000000000000000(0000) GS:ffff9c901f500000(0000) knlGS:0000000000000000
> > > [   54.397130] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > [   54.404585] CR2: 0000000000000000 CR3: 000000000308e000 CR4: 00000000000006e0
> > > [   54.413884] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > [   54.423118] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > [   54.432192] Call Trace:
> > > [   54.435634]  <TASK>
> > > [   54.438512]  ? rcu_torture_stats_print+0x5b2/0x620
> > > [   54.444904]  ? __warn+0x7c/0x130
> > > [   54.449221]  ? rcu_torture_stats_print+0x5b2/0x620
> > > [   54.455737]  ? report_bug+0x171/0x1a0
> > > [   54.460935]  ? handle_bug+0x3c/0x70
> > > [   54.465874]  ? exc_invalid_op+0x17/0x70
> > > [   54.471336]  ? asm_exc_invalid_op+0x1a/0x20
> > > [   54.477092]  ? __pfx_rcu_torture_stats+0x10/0x10
> > > [   54.483472]  ? rcu_torture_stats_print+0x5b2/0x620
> > > [   54.490029]  ? rcu_torture_stats_print+0x28a/0x620
> > > [   54.496565]  ? finish_task_switch.isra.0+0x7e/0x240
> > > [   54.503261]  rcu_torture_stats+0x25/0x70
> > > [   54.508686]  kthread+0xe3/0x110
> > > [   54.513141]  ? __pfx_kthread+0x10/0x10
> > > [   54.518330]  ret_from_fork+0x2c/0x50
> > > [   54.523356]  </TASK>
> > > [   54.526500] ---[ end trace 0000000000000000 ]---
> > >
> > > Also other issues in 6.4.4, I am seeing RCU failures with TREE07 about 40
> > > minutes into the test. This warning indicates that an rcu_torture object from
> > > the rcu_torture pool is still allocated which is an indiciation that RCU is
> > > not working.
> > >
> > > [ 2169.481783] rcu_torture_writer: rtort_pipe_count: 9
> > >
> > > However, if we are to believe the '9', it appears the object did made it
> > > quite some till the end of the pipe array but not until the free pool.
> > >
> > > The full TREE07 splat:
> > > [ 2169.481783] rcu_torture_writer: rtort_pipe_count: 9
> > > [ 2169.489413] WARNING: CPU: 4 PID: 130 at kernel/rcu/rcutorture.c:1584 rcu_torture_writer+0x7f2/0xd80
> > > [ 2169.504064] Modules linked in:
> > > [ 2169.508957] CPU: 4 PID: 130 Comm: rcu_torture_wri Not tainted 6.4.4-g62813c2d2a36 #2
> > > [ 2169.521735] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > [ 2169.540908] RIP: 0010:rcu_torture_writer+0x7f2/0xd80
> > > [ 2169.548542] Code: 15 8b 62 45 02 49 8d 45 e8 48 39 c2 74 bf e8 85 03 08 00 41 8b 55 f8 48 c7 c6 d0 f7 e0 9d 48 c7 c7 d7 7b 28 9e e8 ce 29 f7 ff <0f> 0b 8b 05 9a 48 45 02 85 c0 75 97 89 d8 87 05 8e 48 45 02 85 c0
> > > [ 2169.578445] RSP: 0000:ffffa645804cfe20 EFLAGS: 00010282
> > > [ 2169.586793] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 00000000ffffdfff
> > > [ 2169.598069] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000009ffb
> > > [ 2169.609359] RBP: ffffa645804cff10 R08: 00000000ffffdfff R09: 00000000ffffdfff
> > > [ 2169.620717] R10: ffffffff9e659220 R11: ffffffff9e659220 R12: 0000000000000017
> > > [ 2169.631918] R13: ffffffff9f166b60 R14: 0000000000000000 R15: 0000000000000001
> > > [ 2169.643365] FS:  0000000000000000(0000) GS:ffff8b3a5f300000(0000) knlGS:0000000000000000
> > > [ 2169.655249] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > [ 2169.663207] CR2: 0000000000000000 CR3: 000000001562e000 CR4: 00000000000006e0
> > > [ 2169.672806] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > [ 2169.682194] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > [ 2169.693530] Call Trace:
> > > [ 2169.698054]  <TASK>
> > > [ 2169.701786]  ? rcu_torture_writer+0x7f2/0xd80
> > > [ 2169.708853]  ? __warn+0x7c/0x120
> > > [ 2169.714088]  ? rcu_torture_writer+0x7f2/0xd80
> > > [ 2169.721066]  ? report_bug+0x15d/0x180
> > > [ 2169.726125]  ? handle_bug+0x3c/0x70
> > > [ 2169.730948]  ? exc_invalid_op+0x17/0x70
> > > [ 2169.736238]  ? asm_exc_invalid_op+0x1a/0x20
> > > [ 2169.742047]  ? rcu_torture_writer+0x7f2/0xd80
> > > [ 2169.747907]  ? __pfx_rcu_torture_writer+0x10/0x10
> > > [ 2169.754175]  kthread+0xcb/0xf0
> > > [ 2169.758407]  ? __pfx_kthread+0x10/0x10
> > > [ 2169.763501]  ret_from_fork+0x2c/0x50
> > > [ 2169.768420]  </TASK>
> > > [ 2169.771445] ---[ end trace 0000000000000000 ]---
> > > [ 2169.777698] Dumping ftrace buffer:
> > > [ 2169.782470]    (ftrace buffer empty)
> > > [ 2169.787241] ------------[ cut here ]------------
> > >
> > >
> > > I will continue to monitor and debug these but since I recently re-started
> > > testing stable (my infra was down for a long time), I don't have any
> > > reference for when these started happening.
> > >
> > > thanks,
> > >
> > >  - Joel
> > >