Re: [PATCH] powerpc/powermac: Add missing lockdep_register_key()

From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Erhard F." <erhard_f@mailbox.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/powermac: Add missing lockdep_register_key()
Date: Tue, 30 Nov 2021 15:06:13 +0100	[thread overview]
Message-ID: <c8cbdc08-f37f-5be5-f9ca-68fcd2dc1621@csgroup.eu> (raw)
In-Reply-To: <20211130145318.5fcdf633@yea>

Le 30/11/2021 à 14:53, Erhard F. a écrit :
> On Tue, 30 Nov 2021 10:32:42 +0100
> Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> 
>> KeyWest i2c @0xf8001003 irq 42 /uni-n@f8000000/i2c@f8001000
>> BUG: key c2d00cbc has not been registered!
>> ------------[ cut here ]------------
>> DEBUG_LOCKS_WARN_ON(1)
>> WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:4801 lockdep_init_map_type+0x4c0/0xb4c
>> Modules linked in:
>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.5-gentoo-PowerMacG4 #9
>> NIP:  c01a9428 LR: c01a9428 CTR: 00000000
>> REGS: e1033cf0 TRAP: 0700   Not tainted  (5.15.5-gentoo-PowerMacG4)
>> MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 24002002  XER: 00000000
>>
>> GPR00: c01a9428 e1033db0 c2d1cf20 00000016 00000004 00000001 c01c0630 e1033a73
>> GPR08: 00000000 00000000 00000000 e1033db0 24002004 00000000 f8729377 00000003
>> GPR16: c1829a9c 00000000 18305357 c1416fc0 c1416f80 c006ac60 c2d00ca8 c1416f00
>> GPR24: 00000000 c21586f0 c2160000 00000000 c2d00cbc c2170000 c216e1a0 c2160000
>> NIP [c01a9428] lockdep_init_map_type+0x4c0/0xb4c
>> LR [c01a9428] lockdep_init_map_type+0x4c0/0xb4c
>> Call Trace:
>> [e1033db0] [c01a9428] lockdep_init_map_type+0x4c0/0xb4c (unreliable)
>> [e1033df0] [c1c177b8] kw_i2c_add+0x334/0x424
>> [e1033e20] [c1c18294] pmac_i2c_init+0x9ec/0xa9c
>> [e1033e80] [c1c1a790] smp_core99_probe+0xbc/0x35c
>> [e1033eb0] [c1c03cb0] kernel_init_freeable+0x190/0x5a4
>> [e1033f10] [c000946c] kernel_init+0x28/0x154
>> [e1033f30] [c0035148] ret_from_kernel_thread+0x14/0x1c
>>
>> Add missing lockdep_register_key()
>>
>> Reported-by: Erhard Furtner <erhard_f@mailbox.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/powerpc/platforms/powermac/low_i2c.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/powerpc/platforms/powermac/low_i2c.c b/arch/powerpc/platforms/powermac/low_i2c.c
>> index f77a59b5c2e1..de34fa34c42d 100644
>> --- a/arch/powerpc/platforms/powermac/low_i2c.c
>> +++ b/arch/powerpc/platforms/powermac/low_i2c.c
>> @@ -582,6 +582,7 @@ static void __init kw_i2c_add(struct pmac_i2c_host_kw *host,
>>   	bus->close = kw_i2c_close;
>>   	bus->xfer = kw_i2c_xfer;
>>   	mutex_init(&bus->mutex);
>> +	lockdep_register_key(&bus->lock_key);
>>   	lockdep_set_class(&bus->mutex, &bus->lock_key);
>>   	if (controller == busnode)
>>   		bus->flags = pmac_i2c_multibus;
>> -- 
>> 2.33.1
>>
> 
> The patch applied on 5.15.5 but unfortunately was not enough to fix the lockdep bug.
> 
> Originally was bug #200055 (https://bugzilla.kernel.org/show_bug.cgi?id=200055).
> 

Is that still exactly the same backtrace , ie still pointing to 
kw_i2c_add() ?

Because I see from original bug that in fact the offending commit added 
lockdep_set_class() at 3 places. So it is likely that 
lockdep_register_key() also needs to be added at the two other places.

So if the call trace now gives pmu_i2c_probe() or smu_i2c_probe() then 
you could try and add lockdep_register_key() also there and see if it 
fixes things.

Christophe