From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753772AbbFRKW6 (ORCPT ); Thu, 18 Jun 2015 06:22:58 -0400 Received: from xavier.telenet-ops.be ([195.130.132.52]:57229 "EHLO xavier.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754653AbbFRKWm (ORCPT ); Thu, 18 Jun 2015 06:22:42 -0400 From: Geert Uytterhoeven To: Daniel Lezcano , Thomas Gleixner , "Rafael J. Wysocki" , Kevin Hilman , Ulf Hansson Cc: Magnus Damm , Laurent Pinchart , linux-pm@vger.kernel.org, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code Date: Thu, 18 Jun 2015 12:22:34 +0200 Message-Id: <1434622954-26747-3-git-send-email-geert+renesas@glider.be> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434622954-26747-1-git-send-email-geert+renesas@glider.be> References: <1434622954-26747-1-git-send-email-geert+renesas@glider.be> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If pm_genpd_{add,remove}_device() keeps on failing with -EAGAIN, we end up with an infinite loop in genpd_dev_pm_{at,de}tach(). This may happen due to a genpd.prepared_count imbalance. This is a bug elsewhere, but it will result in a system lock up, possibly during reboot of an otherwise functioning system. To avoid this, put a limit on the maximum number of loop iterations, including a simple back-off mechanism. If the limit is reached, the operation will just fail. An error message is already printed. Signed-off-by: Geert Uytterhoeven --- drivers/base/power/domain.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index cdd547bd67df8218..aa06f60b98b8af35 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -6,6 +6,7 @@ * This file is released under the GPLv2. */ +#include #include #include #include @@ -19,6 +20,9 @@ #include #include +#define GENPD_RETRIES 20 +#define GENPD_DELAY_US 10 + #define GENPD_DEV_CALLBACK(genpd, type, callback, dev) \ ({ \ type (*__routine)(struct device *__d); \ @@ -2131,6 +2135,7 @@ EXPORT_SYMBOL_GPL(of_genpd_get_from_provider); static void genpd_dev_pm_detach(struct device *dev, bool power_off) { struct generic_pm_domain *pd; + unsigned int i; int ret = 0; pd = pm_genpd_lookup_dev(dev); @@ -2139,10 +2144,13 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off) dev_dbg(dev, "removing from PM domain %s\n", pd->name); - while (1) { + for (i = 0; i < GENPD_RETRIES; i++) { ret = pm_genpd_remove_device(pd, dev); if (ret != -EAGAIN) break; + + if (i > GENPD_RETRIES / 2) + udelay(GENPD_DELAY_US); cond_resched(); } @@ -2218,10 +2226,13 @@ int genpd_dev_pm_attach(struct device *dev) dev_dbg(dev, "adding to PM domain %s\n", pd->name); - while (1) { + for (i = 0; i < GENPD_RETRIES; i++) { ret = pm_genpd_add_device(pd, dev); if (ret != -EAGAIN) break; + + if (i > GENPD_RETRIES / 2) + udelay(GENPD_DELAY_US); cond_resched(); } -- 1.9.1 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Date: Thu, 18 Jun 2015 10:22:34 +0000 Subject: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code Message-Id: <1434622954-26747-3-git-send-email-geert+renesas@glider.be> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sh@vger.kernel.org If pm_genpd_{add,remove}_device() keeps on failing with -EAGAIN, we end up with an infinite loop in genpd_dev_pm_{at,de}tach(). This may happen due to a genpd.prepared_count imbalance. This is a bug elsewhere, but it will result in a system lock up, possibly during reboot of an otherwise functioning system. To avoid this, put a limit on the maximum number of loop iterations, including a simple back-off mechanism. If the limit is reached, the operation will just fail. An error message is already printed. Signed-off-by: Geert Uytterhoeven --- drivers/base/power/domain.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index cdd547bd67df8218..aa06f60b98b8af35 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -6,6 +6,7 @@ * This file is released under the GPLv2. */ +#include #include #include #include @@ -19,6 +20,9 @@ #include #include +#define GENPD_RETRIES 20 +#define GENPD_DELAY_US 10 + #define GENPD_DEV_CALLBACK(genpd, type, callback, dev) \ ({ \ type (*__routine)(struct device *__d); \ @@ -2131,6 +2135,7 @@ EXPORT_SYMBOL_GPL(of_genpd_get_from_provider); static void genpd_dev_pm_detach(struct device *dev, bool power_off) { struct generic_pm_domain *pd; + unsigned int i; int ret = 0; pd = pm_genpd_lookup_dev(dev); @@ -2139,10 +2144,13 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off) dev_dbg(dev, "removing from PM domain %s\n", pd->name); - while (1) { + for (i = 0; i < GENPD_RETRIES; i++) { ret = pm_genpd_remove_device(pd, dev); if (ret != -EAGAIN) break; + + if (i > GENPD_RETRIES / 2) + udelay(GENPD_DELAY_US); cond_resched(); } @@ -2218,10 +2226,13 @@ int genpd_dev_pm_attach(struct device *dev) dev_dbg(dev, "adding to PM domain %s\n", pd->name); - while (1) { + for (i = 0; i < GENPD_RETRIES; i++) { ret = pm_genpd_add_device(pd, dev); if (ret != -EAGAIN) break; + + if (i > GENPD_RETRIES / 2) + udelay(GENPD_DELAY_US); cond_resched(); } -- 1.9.1