On 2020-09-10 7:21 a.m., Rob Herring wrote:
> On Wed, Sep 9, 2020 at 8:07 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>> [+cc Mark, Florian, Rob, Scott]
>>
>> On Sat, Aug 01, 2020 at 09:25:49AM +0800, Xingxing Su wrote:
>>> Do not use printk in raw_spinlocks,
>>> it will cause BUG: Invalid wait context.
>>>
>>> The trace reported by lockdep follows.
>>>
>>> [ 2.986113] =============================
>>> [ 2.986115] [ BUG: Invalid wait context ]
>>> [ 2.986116] 5.8.0-rc1+ #11 Not tainted
>>> [ 2.986118] -----------------------------
>>> [ 2.986120] swapper/0/1 is trying to lock:
>>> [ 2.986122] ffffffff80f5ddd8 (console_owner){....}-{3:3}, at: console_unlock+0x284/0x820
>>> [ 2.986130] other info that might help us debug this:
>>> [ 2.986132] context-{5:5}
>>> [ 2.986134] 3 locks held by swapper/0/1:
>>> [ 2.986135] #0: 98000007fa03c990 (&dev->mutex){....}-{0:0}, at: device_driver_attach+0x28/0x90
>>> [ 2.986144] #1: ffffffff80fb83a8 (pci_lock){....}-{2:2}, at: pci_bus_write_config_word+0x60/0xb8
>>> [ 2.986152] #2: ffffffff80f5ded0 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0x1b0/0x3b8
>>> [ 2.986161] stack backtrace:
>>> [ 2.986163] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc1+ #11
>>> [ 2.986164] Stack : 0000000000001d67 98000000030be9b0 0000000000000001 7b2aba74f6c4785b
>>> [ 2.986172] 7b2aba74f6c4785b 0000000000000000 98000007f89cb438 ffffffff80e7dc80
>>> [ 2.986181] 0000000000000001 000000000000000a 0000000000000001 0000000000000001
>>> [ 2.986189] ffffffff80f4e156 fffffffffffffffd ffffffff80cc2d98 fffffffff8000000
>>> [ 2.986197] 0000000024000000 ffffffff80f40000 0000000000000000 0000000000000000
>>> [ 2.986205] ffffffff9500cce0 0000000000000000 ffffffff80f50000 ffffffff81546318
>>> [ 2.986213] ffffffff81c4c3c0 0000000000000018 ffffffffbc000000 0000000000000000
>>> [ 2.986221] ffffffff81340000 98000007f89c8000 98000007f89cb430 98000007f8a00000
>>> [ 2.986229] ffffffff806be568 0000000000000000 0000000000000000 0000000000000000
>>> [ 2.986237] 0000000000000000 0000000000000000 ffffffff80211c1c 7b2aba74f6c4785b
>>> [ 2.986245] ...
>>> [ 2.986250] Call Trace:
>>> [ 2.986251] [<ffffffff80211c1c>] show_stack+0x9c/0x130
>>> [ 2.986253] [<ffffffff806be568>] dump_stack+0xe8/0x150
>>> [ 2.986255] [<ffffffff802ad408>] __lock_acquire+0x570/0x3250
>>> [ 2.986257] [<ffffffff802abed0>] lock_acquire+0x118/0x558
>>> [ 2.986259] [<ffffffff802be764>] console_unlock+0x2e4/0x820
>>> [ 2.986261] [<ffffffff802c0a68>] vprintk_emit+0x1c0/0x3b8
>>> [ 2.986263] [<ffffffff807f45a8>] dev_vprintk_emit+0x1c8/0x210
>>> [ 2.986265] [<ffffffff807f462c>] dev_printk_emit+0x3c/0x60
>>> [ 2.986267] [<ffffffff807f499c>] _dev_warn+0x5c/0x80
>>> [ 2.986269] [<ffffffff806eea9c>] pci_generic_config_write32+0x154/0x160
>>> [ 2.986271] [<ffffffff806edca4>] pci_bus_write_config_word+0x84/0xb8
>>> [ 2.986273] [<ffffffff806f1664>] pci_setup_device+0x22c/0x768
>>> [ 2.986275] [<ffffffff806f26a0>] pci_scan_single_device+0xc8/0x100
>>> [ 2.986277] [<ffffffff806f2788>] pci_scan_slot+0xb0/0x178
>>> [ 2.986279] [<ffffffff806f3ae4>] pci_scan_child_bus_extend+0x5c/0x370
>>> [ 2.986281] [<ffffffff806f407c>] pci_scan_root_bus_bridge+0x6c/0xf0
>>> [ 2.986283] [<ffffffff806f411c>] pci_host_probe+0x1c/0xd8
>>> [ 2.986285] [<ffffffff807fa03c>] platform_drv_probe+0x54/0xb8
>>> [ 2.986287] [<ffffffff807f71f8>] really_probe+0x130/0x388
>>> [ 2.986289] [<ffffffff807f7594>] driver_probe_device+0x64/0xd8
>>> [ 2.986291] [<ffffffff807f7844>] device_driver_attach+0x84/0x90
>>> [ 2.986293] [<ffffffff807f7918>] __driver_attach+0xc8/0x128
>>> [ 2.986295] [<ffffffff807f4cac>] bus_for_each_dev+0x74/0xd8
>>> [ 2.986297] [<ffffffff807f6408>] bus_add_driver+0x170/0x250
>>> [ 2.986299] [<ffffffff807f899c>] driver_register+0x84/0x150
>>> [ 2.986301] [<ffffffff80200b08>] do_one_initcall+0x98/0x458
>>> [ 2.986303] [<ffffffff810212dc>] kernel_init_freeable+0x2c0/0x36c
>>> [ 2.986305] [<ffffffff80be7540>] kernel_init+0x10/0x128
>>> [ 2.986307] [<ffffffff80209d44>] ret_from_kernel_thread+0x14/0x1c
>>>
>>> Signed-off-by: Xingxing Su <suxingxing@xxxxxxxxxxx>
>>> ---
>>> drivers/pci/access.c | 3 ---
>>> 1 file changed, 3 deletions(-)
>>>
>>> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
>>> index 79c4a2e..b3fc164 100644
>>> --- a/drivers/pci/access.c
>>> +++ b/drivers/pci/access.c
>>> @@ -160,9 +160,6 @@ int pci_generic_config_write32(struct pci_bus *bus, unsigned int devfn,
>>> * write happen to have any RW1C (write-one-to-clear) bits set, we
>>> * just inadvertently cleared something we shouldn't have.
>>> */
>>> - dev_warn_ratelimited(&bus->dev, "%d-byte config write to %04x:%02x:%02x.%d offset %#x may corrupt adjacent RW1C bits\n",
>>> - size, pci_domain_nr(bus), bus->number,
>>> - PCI_SLOT(devfn), PCI_FUNC(devfn), where);
>> We just changed this printk (see [1]), but I think we still have this
>> lockdep problem even after Mark's change. So I guess we need another
>> think about this.
>>
>> Maybe we can print something when registering pci_ops that use
>> pci_generic_config_write32()?
> That was my suggestion, but as Mark pointed out that doesn't work if
> pci_generic_config_write32 is wrapped (which is 4 out of 8 cases).
>
> Also, 3 of the cases are only for the root bus (bridge). Are 32-bit
> writes to a bridge going to cause problems? For xgene, interestingly,
> with DT _write32 is needed, but for ACPI it is not (only _read32). I
> think xgene is practically dead though a few people still have
> systems, but likely xgene with DT is really dead. The ECAM case was
> for QCom server which is also pretty much dead. SA1100 nano-engine is
> really old and something only a few people have at most (Russell
> King). So ignoring all those, we're left with just loongson and iproc.
> Maybe just remove the warning?
Yes, removing the warning works fine.
>
> Rob
