Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755226AbdDPHzb (ORCPT ); Sun, 16 Apr 2017 03:55:31 -0400 Received: from mailout1.hostsharing.net ([83.223.95.204]:59831 "EHLO mailout1.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752729AbdDPHz2 (ORCPT ); Sun, 16 Apr 2017 03:55:28 -0400 Date: Sun, 16 Apr 2017 09:55:35 +0200 From: Lukas Wunner To: "Rafael J. Wysocki" Cc: Geert Uytterhoeven , Bjorn Helgaas , Yinghai Lu , Mika Westerberg , Laurent Pinchart , Simon Horman , linux-pci , Linux PM list , Linux-Renesas , "linux-kernel@vger.kernel.org" Subject: Re: PCI / PM: Crashes in PME scan during system suspend Message-ID: <20170416075535.GA6620@wunner.de> References: <2661070.8D7d40DjM3@aspire.rjw.lan> <20170414082249.GA5417@wunner.de> <3960283.lbE9ESSj2m@aspire.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3960283.lbE9ESSj2m@aspire.rjw.lan> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7564 Lines: 164 On Sat, Apr 15, 2017 at 12:27:31AM +0200, Rafael J. Wysocki wrote: > On Friday, April 14, 2017 10:22:49 AM Lukas Wunner wrote: > > Below is a tentative patch which moves PME polling to a freezable > > workqueue, so it is frozen before the host bridge is suspended. > > Geert, Laurent, could you test this? > > > > The patch may be problematic in that pci_pme_list_scan() acquires > > pci_pme_list_mutex, which is also acquired by pci_pme_active(), > > which gets called when devices are suspended -- *after* the worker > > has been frozen. I'm not really familiar with the freezer, can it > > happen that the worker is frozen while holding the mutex? If so > > this would deadlock. Rafael? > > That depends on the worker, precisely on where it calls try_to_freeze(). pci_pme_list_scan() doesn't call try_to_freeze() at all, that's what had me confused. Neither do many other workers that are scheduled to system_freezable_wq. However after familiarizing myself a bit more with the freezer it seems that is fine. The freezer prevents new workers from being scheduled and then schedules the existing workers for up to 20 seconds to allow them to finish. The call to try_to_freeze() is thus only needed for long running workers or for threads which are in some infinite loop. Below is the same patch with a proper commit message, it's mostly copied and pasted from Geert's comprehensive report. Still needs to be tested by Geert and/or Laurent as I was unable reproduce the issue on my x86 laptop. Perhaps on x86 the OS is not responsible for disabling the PCI clock (but presumably the BIOS) or x86 doesn't emit this kind of fault. Thanks, Lukas -- >8 -- Subject: [PATCH] PCI: Freeze PME scan before suspending devices Laurent Pinchart reported that the Renesas R-Car H2 Lager board (r8a7790) crashes during suspend tests. Geert Uytterhoeven managed to reproduce the issue on an M2-W Koelsch board (r8a7791): It occurs when the PME scan runs, once per second. During PME scan, the PCI host bridge (rcar-pci) registers are accessed while its module clock has already been disabled, leading to the crash. The issue only occurs during suspend tests, after writing either "platform" or "processors" to /sys/power/pm_test. It does not (or is less likely) to happen during full system suspend ("core" or "none") because system suspend also disables timers, and thus the workqueue handling PME scans no longer runs. Geert believes the issue may still happen in the small window between disabling module clocks and disabling timers. Rafael Wysocki agrees that PME scans should be suspended before the host bridge registers become inaccessible. To that end, queue the task on a workqueue that gets frozen before devices suspend. How to reproduce: # echo 0 > /sys/module/printk/parameters/console_suspend # echo platform > /sys/power/pm_test # Or "processors" # echo mem > /sys/power/state Make sure CONFIG_PCI_RCAR_GEN2 and CONFIG_USB_OHCI_HCD_PCI are enabled. PM: Syncing filesystems ... [ 38.566237] done. PM: Preparing system for sleep (mem) Freezing user space processes ... [ 38.579813] (elapsed 0.001 seconds) done. Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done. PM: Suspending system (mem) PM: suspend of devices complete after 152.456 msecs PM: late suspend of devices complete after 2.809 msecs PM: noirq suspend of devices complete after 29.863 msecs suspend debug: Waiting for 5 second(s). Unhandled fault: asynchronous external abort (0x1211) at 0x00000000 pgd = c0003000 [00000000] *pgd=80000040004003, *pmd=00000000 Internal error: : 1211 [#1] SMP ARM Modules linked in: CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 4.9.0-rc1-koelsch-00011-g68db9bc814362e7f #3383 Hardware name: Generic R8A7791 (Flattened Device Tree) Workqueue: events pci_pme_list_scan task: eb56e140 task.stack: eb58e000 PC is at pci_generic_config_read+0x64/0x6c LR is at rcar_pci_cfg_base+0x64/0x84 pc : [] lr : [] psr: 600d0093 sp : eb58fe98 ip : c041d750 fp : 00000008 r10: c0e2283c r9 : 00000000 r8 : 600d0013 r7 : 00000008 r6 : eb58fed6 r5 : 00000002 r4 : eb58feb4 r3 : 00000000 r2 : 00000044 r1 : 00000008 r0 : 00000000 Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user Control: 30c5387d Table: 6a9f6c80 DAC: 55555555 Process kworker/1:1 (pid: 20, stack limit = 0xeb58e210) Stack: (0xeb58fe98 to 0xeb590000) fe80: 00000002 00000044 fea0: eb6f5800 c041d9b0 eb58feb4 00000008 00000044 00000000 eb78a000 eb78a000 fec0: 00000044 00000000 eb9aff00 c0424bf0 eb78a000 00000000 eb78a000 c0e22830 fee0: ea8a6fc0 c0424c5c eaae79c0 c0424ce0 eb55f380 c0e22838 eb9a9800 c0235fbc ff00: eb55f380 c0e22838 eb55f380 eb9a9800 eb9a9800 eb58e000 eb9a9824 c0e02100 ff20: eb55f398 c02366c4 eb56e140 eb5631c0 00000000 eb55f380 c023641c 00000000 ff40: 00000000 00000000 00000000 c023a928 cd105598 00000000 40506a34 eb55f380 ff60: 00000000 00000000 dead4ead ffffffff ffffffff eb58ff74 eb58ff74 00000000 ff80: 00000000 dead4ead ffffffff ffffffff eb58ff90 eb58ff90 eb58ffac eb5631c0 ffa0: c023a844 00000000 00000000 c0206d68 00000000 00000000 00000000 00000000 ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 3a81336c 10ccd1dd [] (pci_generic_config_read) from [] (pci_bus_read_config_word+0x58/0x80) [] (pci_bus_read_config_word) from [] (pci_check_pme_status+0x34/0x78) [] (pci_check_pme_status) from [] (pci_pme_wakeup+0x28/0x54) [] (pci_pme_wakeup) from [] (pci_pme_list_scan+0x58/0xb4) [] (pci_pme_list_scan) from [] (process_one_work+0x1bc/0x308) [] (process_one_work) from [] (worker_thread+0x2a8/0x3e0) [] (worker_thread) from [] (kthread+0xe4/0xfc) [] (kthread) from [] (ret_from_fork+0x14/0x2c) Code: ea000000 e5903000 f57ff04f e3a00000 (e5843000) ---[ end trace 667d43ba3aa9e589 ]--- Reported-by: Laurent Pinchart Reported-by: Geert Uytterhoeven Cc: Rafael J. Wysocki Cc: Mika Westerberg Cc: Simon Horman Cc: Yinghai Lu Fixes: df17e62e5bff ("PCI: Add support for polling PME state on suspended legacy PCI devices") Signed-off-by: Lukas Wunner --- drivers/pci/pci.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index aa55501..c561a9e 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1784,8 +1784,8 @@ static void pci_pme_list_scan(struct work_struct *work) } } if (!list_empty(&pci_pme_list)) - schedule_delayed_work(&pci_pme_work, - msecs_to_jiffies(PME_TIMEOUT)); + queue_delayed_work(system_freezable_wq, &pci_pme_work, + msecs_to_jiffies(PME_TIMEOUT)); mutex_unlock(&pci_pme_list_mutex); } @@ -1850,8 +1850,9 @@ void pci_pme_active(struct pci_dev *dev, bool enable) mutex_lock(&pci_pme_list_mutex); list_add(&pme_dev->list, &pci_pme_list); if (list_is_singular(&pci_pme_list)) - schedule_delayed_work(&pci_pme_work, - msecs_to_jiffies(PME_TIMEOUT)); + queue_delayed_work(system_freezable_wq, + &pci_pme_work, + msecs_to_jiffies(PME_TIMEOUT)); mutex_unlock(&pci_pme_list_mutex); } else { mutex_lock(&pci_pme_list_mutex); -- 2.11.0