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Thu, 10 Sep 2020 07:21:17 -0700 (PDT) MIME-Version: 1.0 References: <1596245149-28628-1-git-send-email-suxingxing@loongson.cn> <20200910020742.GA748627@bjorn-Precision-5520> In-Reply-To: <20200910020742.GA748627@bjorn-Precision-5520> From: Rob Herring Date: Thu, 10 Sep 2020 08:21:06 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] PCI: Don't use Printk in raw_spinlocks To: Bjorn Helgaas Cc: Xingxing Su , Bjorn Helgaas , PCI , "linux-kernel@vger.kernel.org" , Mark Tomlinson , Florian Fainelli , Scott Branden Content-Type: text/plain; charset="UTF-8" Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wed, Sep 9, 2020 at 8:07 PM Bjorn Helgaas 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] [] show_stack+0x9c/0x130 > > [ 2.986253] [] dump_stack+0xe8/0x150 > > [ 2.986255] [] __lock_acquire+0x570/0x3250 > > [ 2.986257] [] lock_acquire+0x118/0x558 > > [ 2.986259] [] console_unlock+0x2e4/0x820 > > [ 2.986261] [] vprintk_emit+0x1c0/0x3b8 > > [ 2.986263] [] dev_vprintk_emit+0x1c8/0x210 > > [ 2.986265] [] dev_printk_emit+0x3c/0x60 > > [ 2.986267] [] _dev_warn+0x5c/0x80 > > [ 2.986269] [] pci_generic_config_write32+0x154/0x160 > > [ 2.986271] [] pci_bus_write_config_word+0x84/0xb8 > > [ 2.986273] [] pci_setup_device+0x22c/0x768 > > [ 2.986275] [] pci_scan_single_device+0xc8/0x100 > > [ 2.986277] [] pci_scan_slot+0xb0/0x178 > > [ 2.986279] [] pci_scan_child_bus_extend+0x5c/0x370 > > [ 2.986281] [] pci_scan_root_bus_bridge+0x6c/0xf0 > > [ 2.986283] [] pci_host_probe+0x1c/0xd8 > > [ 2.986285] [] platform_drv_probe+0x54/0xb8 > > [ 2.986287] [] really_probe+0x130/0x388 > > [ 2.986289] [] driver_probe_device+0x64/0xd8 > > [ 2.986291] [] device_driver_attach+0x84/0x90 > > [ 2.986293] [] __driver_attach+0xc8/0x128 > > [ 2.986295] [] bus_for_each_dev+0x74/0xd8 > > [ 2.986297] [] bus_add_driver+0x170/0x250 > > [ 2.986299] [] driver_register+0x84/0x150 > > [ 2.986301] [] do_one_initcall+0x98/0x458 > > [ 2.986303] [] kernel_init_freeable+0x2c0/0x36c > > [ 2.986305] [] kernel_init+0x10/0x128 > > [ 2.986307] [] ret_from_kernel_thread+0x14/0x1c > > > > Signed-off-by: Xingxing Su > > --- > > 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? Rob