Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <002234a5-9829-08bf-20f9-c173b653dca9@roeck-us.net>
Date:   Tue, 14 Mar 2023 09:16:02 -0700
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Subject: Re: Linux 6.3-rc2
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To:     Frederic Weisbecker <frederic@kernel.org>,
        Ard Biesheuvel <ardb@kernel.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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From:   Guenter Roeck <linux@roeck-us.net>
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On 3/14/23 04:18, Frederic Weisbecker wrote:
> Le Mon, Mar 13, 2023 at 05:52:49PM -0700, Guenter Roeck a écrit :
>> On 3/13/23 16:11, Frederic Weisbecker wrote:
>> [   11.360487] WARNING: CPU: 0 PID: 233 at kernel/locking/lockdep.c:5527 check_flags (./arch/arm/include/asm/current.h:36 (discriminator 12) ./include/asm-generic/preempt.h:11 (discriminator 12) kernel/locking/lockdep.c:5528 (discriminator 12))
>> [   11.361102] DEBUG_LOCKS_WARN_ON(current->softirqs_enabled)
>> [   11.361173] Modules linked in:
>> [   11.361730] CPU: 0 PID: 233 Comm: rcS Tainted: G                 N 6.3.0-rc2-dirty #2
>> [   11.361921] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
>> [   11.362303] unwind_backtrace from show_stack (arch/arm/kernel/traps.c:258)
>> [   11.362441] show_stack from dump_stack_lvl (lib/dump_stack.c:107 (discriminator 4))
>> [   11.362519] dump_stack_lvl from __warn (./include/linux/jump_label.h:260 ./include/linux/jump_label.h:270 ./include/trace/events/error_report.h:69 kernel/panic.c:681)
>> [   11.362598] __warn from warn_slowpath_fmt (./arch/arm/include/asm/current.h:36 ./include/asm-generic/preempt.h:16 ./include/asm-generic/preempt.h:59 ./include/linux/context_tracking.h:154 kernel/panic.c:706)
>> [   11.362702] warn_slowpath_fmt from check_flags (./arch/arm/include/asm/current.h:36 (discriminator 12) ./include/asm-generic/preempt.h:11 (discriminator 12) kernel/locking/lockdep.c:5528 (discriminator 12))
>> [   11.362780] check_flags from lock_is_held_type (./arch/arm/include/asm/percpu.h:37 kernel/locking/lockdep.c:462 kernel/locking/lockdep.c:5713)
>> [   11.362851] lock_is_held_type from rcu_read_lock_sched_held (kernel/rcu/update.c:125)
>> [   11.362933] rcu_read_lock_sched_held from trace_rcu_dyntick (./include/trace/events/rcu.h:480 (discriminator 28))
>> [   11.363016] trace_rcu_dyntick from ct_nmi_enter (./arch/arm/include/asm/percpu.h:37 (discriminator 4) ./include/linux/context_tracking_state.h:90 (discriminator 4) kernel/context_tracking.c:301 (discriminator 4))
>> [   11.363108] ct_nmi_enter from irq_enter (kernel/softirq.c:625)
>> [   11.363177] irq_enter from generic_handle_arch_irq (kernel/irq/handle.c:238)
>> [   11.363251] generic_handle_arch_irq from call_with_stack (arch/arm/lib/call_with_stack.S:45)
>> [   11.363339] call_with_stack from __irq_svc (arch/arm/kernel/entry-armv.S:232)
>> [   11.363438] Exception stack(0xd1819f60 to 0xd1819fa8)
>> [   11.363629] 9f60: ecac8b10 40000000 b6f88418 c1c2607c 00000000 40000000 c4acc00b 00000001
>> [   11.363740] 9f80: 00000b00 c0101278 c4acc0f0 00000000 00000051 d1819fb0 c01011c4 c0103c1c
>> [   11.363833] 9fa0: 00000013 ffffffff
>> [   11.363896] __irq_svc from vfp_reload_hw (arch/arm/vfp/vfphw.S:149)
>> [   11.364015] irq event stamp: 1626
>> [   11.364069] hardirqs last enabled at (1625): __und_usr (arch/arm/kernel/entry-armv.S:465)
>> [   11.364199] hardirqs last disabled at (1626): __irq_svc (arch/arm/kernel/entry-armv.S:221)
>> [   11.364290] softirqs last enabled at (1424): __do_softirq (./arch/arm/include/asm/current.h:36 ./include/asm-generic/preempt.h:11 kernel/softirq.c:415 kernel/softirq.c:600)
>> [   11.364396] softirqs last disabled at (1323): __irq_exit_rcu (kernel/softirq.c:445 kernel/softirq.c:650)
>> [   11.364494] ---[ end trace 0000000000000000 ]---
>> [   11.364637] preempt_count(): 201 softirq_count(): 200
>>                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> Ok so this is a softirq disabled section that doesn't handle the lockdep
> part.
> 
> How does the following look like as a culprit?
> 
> 62b95a7b44d1 (ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled)
> 

Indeed, reverting this patch on top of v6.3-rc2 fixes the problem.

Guenter