From patchwork Tue Mar 24 12:20:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Shevchenko X-Patchwork-Id: 11455255 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 11B051392 for ; Tue, 24 Mar 2020 12:20:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCCE520870 for ; Tue, 24 Mar 2020 12:20:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727161AbgCXMU2 (ORCPT ); Tue, 24 Mar 2020 08:20:28 -0400 Received: from mga11.intel.com ([192.55.52.93]:13016 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727420AbgCXMU2 (ORCPT ); Tue, 24 Mar 2020 08:20:28 -0400 IronPort-SDR: 3HgwvjiWL0NtK3dNvDHwfC8kcRW2Riyr7+tNBK0srLfBxKzavpfzLdSWzs5d0CzQPkY56KDYGQ qBLE5MZXrc6Q== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 05:20:27 -0700 IronPort-SDR: UCKqisdiJ7xSTDSNTIyKAKk85Vkrf8wD2zF/vUyCMrhSLjn36P0q0659H2Mv45cvJSfYiOWsqM qJcajgqe1MxA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,300,1580803200"; d="scan'208";a="240044056" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga008.fm.intel.com with ESMTP; 24 Mar 2020 05:20:25 -0700 Received: by black.fi.intel.com (Postfix, from userid 1003) id 7DE1E11D; Tue, 24 Mar 2020 14:20:24 +0200 (EET) From: Andy Shevchenko To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , linux-pm@vger.kernel.org Cc: Andy Shevchenko , Artem Bityutskiy , Mark Brown , Felipe Balbi , Andrzej Hajda , Peter Ujfalusi , Ferry Toth Subject: [PATCH v2 1/3] driver core: Break infinite loop when deferred probe can't be satisfied Date: Tue, 24 Mar 2020 14:20:21 +0200 Message-Id: <20200324122023.9649-1-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Consider the following scenario. The main driver of USB OTG controller (dwc3-pci), which has the following functional dependencies on certain platform: - ULPI (tusb1210) - extcon (tested with extcon-intel-mrfld) Note, that first driver, tusb1210, is available at the moment of dwc3-pci probing, while extcon-intel-mrfld is built as a module and won't appear till user space does something about it. This is depicted by kernel configuration excerpt: CONFIG_PHY_TUSB1210=y CONFIG_USB_DWC3=y CONFIG_USB_DWC3_ULPI=y CONFIG_USB_DWC3_DUAL_ROLE=y CONFIG_USB_DWC3_PCI=y CONFIG_EXTCON_INTEL_MRFLD=m In the Buildroot environment the modules are probed by alphabetical ordering of their modaliases. The latter comes to the case when USB OTG driver will be probed first followed by extcon one. So, if the platform anticipates extcon device to be appeared, in the above case we will get deferred probe of USB OTG, because of ordering. Since current implementation, done by the commit 58b116bce136 ("drivercore: deferral race condition fix") counts the amount of triggered deferred probe, we never advance the situation -- the change makes it to be an infinite loop. ---8<---8<--- [ 22.187127] driver_deferred_probe_trigger <<< 1 ...here is the late initcall triggers deferred probe... [ 22.191725] platform dwc3.0.auto: deferred_probe_work_func in deferred list ...dwc3.0.auto is the only device in the deferred list... [ 22.198727] platform dwc3.0.auto: deferred_probe_work_func 1 <<< counter 1 ...the counter before mutex is unlocked is kept the same... [ 22.205663] platform dwc3.0.auto: Retrying from deferred list ...mutes has been unlocked, we try to re-probe the driver... [ 22.211487] bus: 'platform': driver_probe_device: matched device dwc3.0.auto with driver dwc3 [ 22.220060] bus: 'platform': really_probe: probing driver dwc3 with device dwc3.0.auto [ 22.238735] bus: 'ulpi': driver_probe_device: matched device dwc3.0.auto.ulpi with driver tusb1210 [ 22.247743] bus: 'ulpi': really_probe: probing driver tusb1210 with device dwc3.0.auto.ulpi [ 22.256292] driver: 'tusb1210': driver_bound: bound to device 'dwc3.0.auto.ulpi' [ 22.263723] driver_deferred_probe_trigger <<< 2 ...the dwc3.0.auto probes ULPI, we got successful bound and bumped counter... [ 22.268304] bus: 'ulpi': really_probe: bound device dwc3.0.auto.ulpi to driver tusb1210 [ 22.276697] platform dwc3.0.auto: Driver dwc3 requests probe deferral ...but extcon driver is still missing... [ 22.283174] platform dwc3.0.auto: Added to deferred list [ 22.288513] platform dwc3.0.auto: driver_deferred_probe_add_trigger local counter: 1 new counter 2 ...and since we had a successful probe, we got counter mismatch... [ 22.297490] driver_deferred_probe_trigger <<< 3 [ 22.302074] platform dwc3.0.auto: deferred_probe_work_func 2 <<< counter 3 ...at the end we have a new counter and loop repeats again, see 22.198727... ---8<---8<--- Revert of the commit helps, but it is probably not helpful for the initially found regression. Artem Bityutskiy suggested to use counter of the successful probes instead. This fixes above mentioned case and shouldn't prevent driver to reprobe deferred ones. Fixes: 58b116bce136 ("drivercore: deferral race condition fix") Suggested-by: Artem Bityutskiy Cc: Grant Likely grant.likely@arm.com Cc: Greg Kroah-Hartman Cc: Mark Brown Cc: Felipe Balbi Cc: Andrzej Hajda Signed-off-by: Andy Shevchenko Reviewed-by: Peter Ujfalusi Tested-by: Ferry Toth --- v2: picked up tags, update Grant's email (Peter) drivers/base/dd.c | 39 +++++++++++++++++++++------------------ 1 file changed, 21 insertions(+), 18 deletions(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index b25bcab2a26b..43720beb5300 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -53,7 +53,6 @@ static DEFINE_MUTEX(deferred_probe_mutex); static LIST_HEAD(deferred_probe_pending_list); static LIST_HEAD(deferred_probe_active_list); -static atomic_t deferred_trigger_count = ATOMIC_INIT(0); static struct dentry *deferred_devices; static bool initcalls_done; @@ -147,17 +146,6 @@ static bool driver_deferred_probe_enable = false; * This functions moves all devices from the pending list to the active * list and schedules the deferred probe workqueue to process them. It * should be called anytime a driver is successfully bound to a device. - * - * Note, there is a race condition in multi-threaded probe. In the case where - * more than one device is probing at the same time, it is possible for one - * probe to complete successfully while another is about to defer. If the second - * depends on the first, then it will get put on the pending list after the - * trigger event has already occurred and will be stuck there. - * - * The atomic 'deferred_trigger_count' is used to determine if a successful - * trigger has occurred in the midst of probing a driver. If the trigger count - * changes in the midst of a probe, then deferred processing should be triggered - * again. */ static void driver_deferred_probe_trigger(void) { @@ -170,7 +158,6 @@ static void driver_deferred_probe_trigger(void) * into the active list so they can be retried by the workqueue */ mutex_lock(&deferred_probe_mutex); - atomic_inc(&deferred_trigger_count); list_splice_tail_init(&deferred_probe_pending_list, &deferred_probe_active_list); mutex_unlock(&deferred_probe_mutex); @@ -350,6 +337,19 @@ static void __exit deferred_probe_exit(void) } __exitcall(deferred_probe_exit); +/* + * Note, there is a race condition in multi-threaded probe. In the case where + * more than one device is probing at the same time, it is possible for one + * probe to complete successfully while another is about to defer. If the second + * depends on the first, then it will get put on the pending list after the + * trigger event has already occurred and will be stuck there. + * + * The atomic 'probe_okay' is used to determine if a successful probe has + * occurred in the midst of probing another driver. If the count changes in + * the midst of a probe, then deferred processing should be triggered again. + */ +static atomic_t probe_okay = ATOMIC_INIT(0); + /** * device_is_bound() - Check if device is bound to a driver * @dev: device to check @@ -375,6 +375,7 @@ static void driver_bound(struct device *dev) pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name, __func__, dev_name(dev)); + atomic_inc(&probe_okay); klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); device_links_driver_bound(dev); @@ -481,18 +482,18 @@ static atomic_t probe_count = ATOMIC_INIT(0); static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue); static void driver_deferred_probe_add_trigger(struct device *dev, - int local_trigger_count) + int local_probe_okay_count) { driver_deferred_probe_add(dev); /* Did a trigger occur while probing? Need to re-trigger if yes */ - if (local_trigger_count != atomic_read(&deferred_trigger_count)) + if (local_probe_okay_count != atomic_read(&probe_okay)) driver_deferred_probe_trigger(); } static int really_probe(struct device *dev, struct device_driver *drv) { int ret = -EPROBE_DEFER; - int local_trigger_count = atomic_read(&deferred_trigger_count); + int local_probe_okay_count = atomic_read(&probe_okay); bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) && !drv->suppress_bind_attrs; @@ -509,7 +510,7 @@ static int really_probe(struct device *dev, struct device_driver *drv) ret = device_links_check_suppliers(dev); if (ret == -EPROBE_DEFER) - driver_deferred_probe_add_trigger(dev, local_trigger_count); + driver_deferred_probe_add_trigger(dev, local_probe_okay_count); if (ret) return ret; @@ -619,7 +620,7 @@ static int really_probe(struct device *dev, struct device_driver *drv) case -EPROBE_DEFER: /* Driver requested deferred probing */ dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name); - driver_deferred_probe_add_trigger(dev, local_trigger_count); + driver_deferred_probe_add_trigger(dev, local_probe_okay_count); break; case -ENODEV: case -ENXIO: @@ -1148,6 +1149,8 @@ static void __device_release_driver(struct device *dev, struct device *parent) dev_pm_set_driver_flags(dev, 0); klist_remove(&dev->p->knode_driver); + atomic_dec(&probe_okay); + device_pm_check_callbacks(dev); if (dev->bus) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, From patchwork Tue Mar 24 12:20:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Shevchenko X-Patchwork-Id: 11455257 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B165C1392 for ; Tue, 24 Mar 2020 12:20:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9CE4E208C3 for ; Tue, 24 Mar 2020 12:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727332AbgCXMUc (ORCPT ); Tue, 24 Mar 2020 08:20:32 -0400 Received: from mga03.intel.com ([134.134.136.65]:4902 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727337AbgCXMU1 (ORCPT ); Tue, 24 Mar 2020 08:20:27 -0400 IronPort-SDR: 1J91S85GuyxS5YgY+RtGbMTfxETyAllcemjRweYFN8BoAiamCW390/dbcSmsyBKhRE/ze6V/pv dviBsTtGLq9A== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 05:20:27 -0700 IronPort-SDR: w2UuZHQPtrOYo+rz0+T7luwq1AAVIMGhLOr4bvz8eNrs2Xvw95XhmtqM9EAaG0mr35bSIFQC6b mjCD6BFnRdAg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,300,1580803200"; d="scan'208";a="447859322" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga006.fm.intel.com with ESMTP; 24 Mar 2020 05:20:25 -0700 Received: by black.fi.intel.com (Postfix, from userid 1003) id 8E01D65; Tue, 24 Mar 2020 14:20:24 +0200 (EET) From: Andy Shevchenko To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , linux-pm@vger.kernel.org Cc: Andy Shevchenko , Ferry Toth Subject: [PATCH v2 2/3] driver core: Read atomic counter once in driver_probe_done() Date: Tue, 24 Mar 2020 14:20:22 +0200 Message-Id: <20200324122023.9649-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200324122023.9649-1-andriy.shevchenko@linux.intel.com> References: <20200324122023.9649-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Between printing the debug message and actual check atomic counter can be altered. For better debugging experience read atomic counter value only once. Signed-off-by: Andy Shevchenko Tested-by: Ferry Toth Reviewed-by: Rafael J. Wysocki --- v2: picked up tags drivers/base/dd.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 43720beb5300..efd0e4c16ba5 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -669,9 +669,10 @@ static int really_probe_debug(struct device *dev, struct device_driver *drv) */ int driver_probe_done(void) { - pr_debug("%s: probe_count = %d\n", __func__, - atomic_read(&probe_count)); - if (atomic_read(&probe_count)) + int local_probe_count = atomic_read(&probe_count); + + pr_debug("%s: probe_count = %d\n", __func__, local_probe_count); + if (local_probe_count) return -EBUSY; return 0; } From patchwork Tue Mar 24 12:20:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Shevchenko X-Patchwork-Id: 11455253 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4BADC14B4 for ; Tue, 24 Mar 2020 12:20:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 369072080C for ; Tue, 24 Mar 2020 12:20:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727376AbgCXMU1 (ORCPT ); Tue, 24 Mar 2020 08:20:27 -0400 Received: from mga01.intel.com ([192.55.52.88]:33838 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727161AbgCXMU1 (ORCPT ); Tue, 24 Mar 2020 08:20:27 -0400 IronPort-SDR: 4bj7BVe2fsrnKU2IHOxZNn7RU9Z6+cFxeQFTMYk7h64xVnBdm9GLIYPf/FXfetFdaSUEfY+1dj SHcckQpV9HHQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 05:20:26 -0700 IronPort-SDR: QrKiMwNd8E1VplOjPkJMHyaiCbhHS8lmlleMbrQ6JC6wLiVwJwanrbvQPrX0bQXEQVnSomXjxT 4tXaI7YD5qBA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,300,1580803200"; d="scan'208";a="238218894" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga007.fm.intel.com with ESMTP; 24 Mar 2020 05:20:25 -0700 Received: by black.fi.intel.com (Postfix, from userid 1003) id 939D214B; Tue, 24 Mar 2020 14:20:24 +0200 (EET) From: Andy Shevchenko To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , linux-pm@vger.kernel.org Cc: Andy Shevchenko Subject: [PATCH v2 3/3] driver core: Replace open-coded list_last_entry() Date: Tue, 24 Mar 2020 14:20:23 +0200 Message-Id: <20200324122023.9649-3-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200324122023.9649-1-andriy.shevchenko@linux.intel.com> References: <20200324122023.9649-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org There is a place in the code where open-coded version of list entry accessors list_last_entry() is used. Replace that with the standard macro. Signed-off-by: Andy Shevchenko Reviewed-by: Rafael J. Wysocki --- v2: no change drivers/base/dd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index efd0e4c16ba5..27a4d51b5bba 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -1226,7 +1226,7 @@ void driver_detach(struct device_driver *drv) spin_unlock(&drv->p->klist_devices.k_lock); break; } - dev_prv = list_entry(drv->p->klist_devices.k_list.prev, + dev_prv = list_last_entry(&drv->p->klist_devices.k_list, struct device_private, knode_driver.n_node); dev = dev_prv->device;