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Message-ID: <20230703-dupe-frying-79ae2ccf94eb@spud>
Date: Mon, 3 Jul 2023 18:00:08 +0100
From: Conor Dooley <conor@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: lkp <oliver.sang@...el.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
lkp@...el.com
Subject: Re: [mm] 408579cd62: WARNING:suspicious_RCU_usage
Hey Linus,
On Sun, Jul 02, 2023 at 09:34:35PM -0700, Linus Torvalds wrote:
> On Sun, 2 Jul 2023 at 19:04, kernel test robot <oliver.sang@...el.com> wrote:
> >
> > commit: 408579cd627a15bd703fe3eeb8485fd02726e9d3 ("mm: Update do_vmi_align_munmap() return semantics")
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> >
> > in testcase: boot
> >
> > on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> >
> > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> >
> >
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kernel test robot <oliver.sang@...el.com>
I'm not entirely sure if it is related, as stuff in the guts of mm like
this is beyond me, but I've been seeing similar warnings on RISC-V. This
is the only hit on lore for "lib/maple_tree.c:{860,816} suspicious
rcu_dereference_check() usage!", so I figured it might be. Apologies if
not!
Running RCU synchronous self tests
Running RCU synchronous self tests
RCU Tasks: Setting shift to 4 and lim to 1 rcu_task_cb_adjust=1.
RCU Tasks Trace: Setting shift to 4 and lim to 1 rcu_task_cb_adjust=1.
Running RCU-tasks wait API self tests
riscv: ELF compat mode supported
ASID allocator using 16 bits (65536 entries)
rcu: Hierarchical SRCU implementation.
rcu: Max phase no-delay instances is 1000.
EFI services will not be available.
Callback from call_rcu_tasks_trace() invoked.
smp: Bringing up secondary CPUs ...
=============================
WARNING: suspicious RCU usage
6.4.0-10173-ga901a3568fd2 #1 Not tainted
-----------------------------
lib/maple_tree.c:860 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
RCU used illegally from offline CPU!
rcu_scheduler_active = 1, debug_locks = 1
1 lock held by swapper/1/0:
#0: ffffffff8169ceb0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x32
stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.4.0-10173-ga901a3568fd2 #1
Hardware name: riscv-virtio,qemu (DT)
Call Trace:
[<ffffffff80006a20>] show_stack+0x2c/0x38
[<ffffffff80af3ee0>] dump_stack_lvl+0x5e/0x80
[<ffffffff80af3f16>] dump_stack+0x14/0x1c
[<ffffffff80083ff0>] lockdep_rcu_suspicious+0x19e/0x232
[<ffffffff80ad4802>] mtree_load+0x18a/0x3b6
[<ffffffff80091632>] __irq_get_desc_lock+0x2c/0x82
[<ffffffff80094722>] enable_percpu_irq+0x36/0x9e
[<ffffffff800087d4>] riscv_ipi_enable+0x32/0x4e
[<ffffffff80008692>] smp_callin+0x24/0x66
=============================
WARNING: suspicious RCU usage
6.4.0-10173-ga901a3568fd2 #1 Not tainted
-----------------------------
lib/maple_tree.c:816 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
RCU used illegally from offline CPU!
rcu_scheduler_active = 1, debug_locks = 1
1 lock held by swapper/1/0:
#0: ffffffff8169ceb0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x32
stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.4.0-10173-ga901a3568fd2 #1
Hardware name: riscv-virtio,qemu (DT)
Call Trace:
[<ffffffff80006a20>] show_stack+0x2c/0x38
[<ffffffff80af3ee0>] dump_stack_lvl+0x5e/0x80
[<ffffffff80af3f16>] dump_stack+0x14/0x1c
[<ffffffff80083ff0>] lockdep_rcu_suspicious+0x19e/0x232
[<ffffffff80ad4932>] mtree_load+0x2ba/0x3b6
[<ffffffff80091632>] __irq_get_desc_lock+0x2c/0x82
[<ffffffff80094722>] enable_percpu_irq+0x36/0x9e
[<ffffffff800087d4>] riscv_ipi_enable+0x32/0x4e
[<ffffffff80008692>] smp_callin+0x24/0x66
smp: Brought up 1 node, 16 CPUs
> > [ 215.088258][ T1] WARNING: suspicious RCU usage
>
> I think the
>
> validate_mm(mm);
>
> call (mm/mmap.c:2561) needs to be moved up to before the
>
> if (unlock)
> mmap_read_unlock(mm);
>
> that is just a couple of lines earlier.
>
> Can you verify that that fixes the warning?
I can't speak for Oliver & LKP, but that change didn't fix it for me,
although my issue could be different of course.
Cheers,
Conor.
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