From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: [PATCH v2 3/9] driver core: Do not resume suppliers under device_links_write_lock()
Date: Fri, 01 Feb 2019 01:47:53 +0100
Message-ID: <3345126.YDF5Jo2U6B@aspire.rjw.lan>
References: <1952449.TVsm6CJCTy@aspire.rjw.lan>
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To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Linux PM <linux-pm@vger.kernel.org>, Ulf Hansson <ulf.hansson@linaro.org>, Daniel Vetter <daniel@ffwll.ch>, Lukas Wunner <lukas@wunner.de>, Andrzej Hajda <a.hajda@samsung.com>, Russell King - ARM Linux <linux@armlinux.org.uk>, Lucas Stach <l.stach@pengutronix.de>, Linus Walleij <linus.walleij@linaro.org>, Thierry Reding <thierry.reding@gmail.com>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, Marek Szyprowski <m.szyprowski@samsung.com>, Joerg Roedel <jroedel@suse.de>
List-Id: linux-pm@vger.kernel.org

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

It is incorrect to call pm_runtime_get_sync() under
device_links_write_lock(), because it may end up trying to take
device_links_read_lock() while resuming the target device and that
will deadlock in the non-SRCU case, so avoid that by resuming the
supplier device in device_link_add() before calling
device_links_write_lock().

Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
Fixes: baa8809f6097 ("PM / runtime: Optimize the use of device links")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/base/core.c |   20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/base/core.c
===================================================================
--- linux-pm.orig/drivers/base/core.c
+++ linux-pm/drivers/base/core.c
@@ -201,12 +201,21 @@ struct device_link *device_link_add(stru
 				    struct device *supplier, u32 flags)
 {
 	struct device_link *link;
+	bool rpm_put_supplier = false;
 
 	if (!consumer || !supplier ||
 	    (flags & DL_FLAG_STATELESS &&
 	     flags & (DL_FLAG_AUTOREMOVE_CONSUMER | DL_FLAG_AUTOREMOVE_SUPPLIER)))
 		return NULL;
 
+	if (flags & DL_FLAG_PM_RUNTIME && flags & DL_FLAG_RPM_ACTIVE) {
+		if (pm_runtime_get_sync(supplier) < 0) {
+			pm_runtime_put_noidle(supplier);
+			return NULL;
+		}
+		rpm_put_supplier = true;
+	}
+
 	device_links_write_lock();
 	device_pm_lock();
 
@@ -250,13 +259,8 @@ struct device_link *device_link_add(stru
 
 	if (flags & DL_FLAG_PM_RUNTIME) {
 		if (flags & DL_FLAG_RPM_ACTIVE) {
-			if (pm_runtime_get_sync(supplier) < 0) {
-				pm_runtime_put_noidle(supplier);
-				kfree(link);
-				link = NULL;
-				goto out;
-			}
 			link->rpm_active = true;
+			rpm_put_supplier = false;
 		}
 		pm_runtime_new_link(consumer);
 		/*
@@ -328,6 +332,10 @@ struct device_link *device_link_add(stru
  out:
 	device_pm_unlock();
 	device_links_write_unlock();
+
+	if (rpm_put_supplier)
+		pm_runtime_put(supplier);
+
 	return link;
 }
 EXPORT_SYMBOL_GPL(device_link_add);