linux-kernel - [PATCH v2 1/2] kobject: delay kobject release for random time

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Message-ID: <20131206003751.28684.32460.stgit@bhelgaas-glaptop.roam.corp.google.com>
Date:	Thu, 05 Dec 2013 17:37:51 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Veaceslav Falico <vfalico@...hat.com>,
	Russell King <linux@....linux.org.uk>,
	Neil Horman <nhorman@...driver.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Zdenek Kabelac <zkabelac@...hat.com>
Subject: [PATCH v2 1/2] kobject: delay kobject release for random time

When CONFIG_DEBUG_KOBJECT_RELEASE=y, delay kobject release functions for a
random time between 1 and 8 seconds, which effectively changes the order in
which they're called.

Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 lib/kobject.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/kobject.c b/lib/kobject.c
index 962175134702..bc73312ac797 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -17,6 +17,7 @@
 #include <linux/export.h>
 #include <linux/stat.h>
 #include <linux/slab.h>
+#include <linux/random.h>
 
 /*
  * populate_dir - populate directory with attributes.
@@ -592,10 +593,13 @@ static void kobject_release(struct kref *kref)
 {
 	struct kobject *kobj = container_of(kref, struct kobject, kref);
 #ifdef CONFIG_DEBUG_KOBJECT_RELEASE
-	pr_debug("kobject: '%s' (%p): %s, parent %p (delayed)\n",
-		 kobject_name(kobj), kobj, __func__, kobj->parent);
+	unsigned long delay = HZ + HZ * (get_random_int() & 0x3);
+
+	pr_debug("kobject: '%s' (%p): %s, parent %p (delayed %ld)\n",
+		 kobject_name(kobj), kobj, __func__, kobj->parent, delay);
 	INIT_DELAYED_WORK(&kobj->release, kobject_delayed_cleanup);
-	schedule_delayed_work(&kobj->release, HZ);
+
+	schedule_delayed_work(&kobj->release, delay);
 #else
 	kobject_cleanup(kobj);
 #endif

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