On Tue, Aug 04, 2015 at 10:05:18AM -0400, Jarod Wilson wrote: > On Mon, Aug 3, 2015 at 12:14 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > > > On Tue, Jul 21, 2015 at 12:25:30PM -0400, Jarod Wilson wrote: > > > https://bugzilla.kernel.org/show_bug.cgi?id=99841 > > > > > > Seems like a read of all 1's from a register of a device that has gone > > > away should be taken as a sign that the device has gone away. > > > Section 6.2.10 of the PCIE spec (v4.0, rev 0.3, Feb 19, 2014) suggests as > > > much with this snippet: > > > > > > |IMPLEMENTATION NOTE > > > |Data Value of All 1’s > > > |Many platforms, including those supporting RP Extensions for DPC, can > > > |return a data value of all 1’s to software when an error is associated > > > |with a PCI Express Configuration, I/O, or Memory Read Request. During > > DPC, > > > |the Downstream Port discards Requests destined for the Link and > > completes > > > |them with an error (i.e., either with an Unsupported Request (UR) or > > > |Completer Abort (CA) Completion Status). By ending a series of MMIO or > > > |configuration space operations with a read to an address with a known > > > |data value not equal to all 1’s, software may determine if a Completer > > > |has been removed or DPC has been triggered. > > > > > > I'm not sure the above is directly relevant to this case, but the same > > > principle (reading all 1's means the device is probably gone) seems to > > > hold. > > > > > > This is based on part of a debugging patch Bjorn posted in the referenced > > > bugzilla, and its required to make the HP ZBook G2 I've got here not barf > > > when disconnecting a thunderbolt ethernet adapter and corrupt memory. > > > > > > Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > > CC: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > > CC: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > > CC: linux-pci@xxxxxxxxxxxxxxx > > > Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx> > > > > Hi Jarod, > > > > I think there are two issues here: > > > > 1) pciehp doesn't handle all 1's correctly > > 2) use-after-free of hotplug_slot > > > > This patch is for the first issue. I think it's correct, but I still > > have a question or two. I attached an updated version of the patch > > and changelog. > > > > Here's the path I think we're taking: 03:03.0 receives pciehp > > interrupt for removal (link down and card not present), and we call > > pciehp_unconfigure_device() for 05:00.0 and everything downstream from > > it. Part of this is removing 06:00.0. I expected this would use this > > path: > > > > pcie_port_remove_service # .remove method for 06:00.0 > > dev_printk("unloading service driver ...") > > pciehp_remove # hpdriver_portdrv.remove > > pciehp_release_ctrl > > pcie_shutdown_notification > > pcie_disable_notification > > pcie_write_cmd > > pcie_do_write_cmd(..., true) # wait > > pcie_wait_cmd > > pcie_poll_cmd > > read PCI_EXP_SLTSTA # would get 0xffff > > read PCI_EXPT_SLTCTL # would get 0xffff > > > > so I added checks for ~0 data in pcie_poll_cmd() and > > pcie_do_write_cmd(). > > > > But the dmesg log shows that we were in pcie_isr(), and I don't > > understand yet how we got there. Can you help figure that out? Maybe > > put a dump_stack() in pcie_isr() or something? > > [ 1949.102247] pciehp 0000:03:03.0:pcie24: pcie_isr: intr_loc 108 > [ 1949.102252] pciehp 0000:03:03.0:pcie24: Presence/Notify input change > [ 1949.102256] pciehp 0000:03:03.0:pcie24: Card not present on Slot(3) > [ 1949.102262] pciehp 0000:03:03.0:pcie24: Data Link Layer State change > [ 1949.102266] pciehp 0000:03:03.0:pcie24: slot(3): Link Down event > [ 1949.102281] pciehp 0000:03:03.0:pcie24: Surprise Removal > [ 1949.102286] pciehp 0000:03:03.0:pcie24: Link Down event ignored on > slot(3): already powering off > [ 1949.102288] pciehp 0000:03:03.0:pcie24: Disabling > domain:bus:device=0000:05:00 > [ 1949.102290] pciehp 0000:03:03.0:pcie24: pciehp_unconfigure_device: > domain:bus:dev = 0000:05:00 > [ 1950.321907] tg3 0000:07:00.0: tg3_abort_hw timed out, TX_MODE_ENABLE > will not clear MAC_TX_MODE=ffffffff > [ 1950.525986] [sched_delayed] sched: RT throttling activated > [ 1950.544164] pciehp 0000:06:00.0:pcie24: unloading service driver pciehp > [ 1950.544170] pciehp 0000:06:00.0:pcie24: release_slot: physical_slot = 9 > [ 1950.545016] pciehp 0000:06:00.0:pcie24: Timeout on hotplug command > 0x1038 (issued 19092 msec ago) > [ 1950.545020] pciehp 0000:06:00.0:pcie24: pcie_do_write_cmd: no response > from device > [ 1950.545021] pciehp 0000:06:00.0:pcie24: pcie_disable_notification: > SLOTCTRL d8 write cmd 0 > [ 1950.545025] pciehp 0000:06:00.0:pcie24: Device has gone away > [ 1950.545027] CPU: 0 PID: 12361 Comm: kworker/0:2 Not tainted > 3.10.0-302.el7.hp.x86_64 #1 > [ 1950.545028] Hardware name: Hewlett-Packard HP ZBook 15 G2/2253, BIOS M70 > Ver. 01.07 02/26/2015 > [ 1950.545033] Workqueue: pciehp-3 pciehp_power_thread > [ 1950.545034] 0000000000000000 00000000f721dd13 ffff8804822ffa78 > ffffffff81632729 > [ 1950.545036] ffff8804822ffac0 ffffffff8133bf64 ffff00000000002e > 00000000f721dd13 > [ 1950.545038] ffff8804818fab00 ffff880468f70cc0 000000000000002e > 0000000000000282 > [ 1950.545039] Call Trace: > [ 1950.545044] [<ffffffff81632729>] dump_stack+0x19/0x1b > [ 1950.545046] [<ffffffff8133bf64>] pcie_isr+0x264/0x280 > [ 1950.545048] [<ffffffff8111b6b9>] __free_irq+0x189/0x220 > [ 1950.545049] [<ffffffff8111b7e9>] free_irq+0x49/0xb0 > [ 1950.545051] [<ffffffff8133d3b9>] pciehp_release_ctrl+0xb9/0xe0 > [ 1950.545053] [<ffffffff81339db3>] pciehp_remove+0x23/0x30 > [ 1950.545055] [<ffffffff8133442e>] pcie_port_remove_service+0x4e/0x60 Do you have CONFIG_DEBUG_SHIRQ set? When CONFIG_DEBUG_SHIRQ is set, __free_irq() calls the ISR one last time. It does make sense that the driver must be prepared for the ISR to be called at any time before free_irq() returns. I just didn't see a path for the already-removed device to generate an actual interrupt. Can you try the version I posted, with the additional tests in pcie_poll_cmd() and pcie_do_write_cmd()? We should try to read from the device there, even before we free the IRQ, so we might see several messages. Maybe there's a way we can be smarter about bailing out there. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
