linux-kernel - [RFC PATCH 03/11] drivers/base: convert deferred_trigger_count and probe_count to counter

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Message-Id: <576d5405373295b147a876006df6842f31d64b8a.1600816121.git.skhan@linuxfoundation.org>
Date:   Tue, 22 Sep 2020 19:43:32 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     gregkh@...uxfoundation.org, rafael@...nel.org,
        keescook@...omium.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH 03/11] drivers/base: convert deferred_trigger_count and probe_count to counter_atomic

counter_atomic is introduced to be used when a variable is used as
a simple counter and doesn't guard object lifetimes. This clearly
differentiates atomic_t usages that guard object lifetimes.

counter_atomic variables will wrap around to 0 when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

deferred_trigger_count gets incremented and read. It doesn't guard
object lifetimes, device usage counts, device open counts, and pm
states. There is very little chance of this counter overflowing.
Convert it to use counter_atomic.

This conversion doesn't change the oveflow wrap around behavior.

probe_count gets incremented, decremented, read. It doesn't guard
object lifetimes, device usage counts, device open counts, and pm
states. There is very little chance of this counter overflowing.
This counter controls the wait for known devices to complete their
probing, and probe_count == 0 ends the wait. Other than that it
meets the other criteria to be converted. Convert it to use
counter_atomic.

Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 drivers/base/dd.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 857b0a928e8d..f49fe45960ac 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -28,6 +28,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/pinctrl/devinfo.h>
 #include <linux/slab.h>
+#include <linux/counters.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -54,7 +55,7 @@
 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 counter_atomic deferred_trigger_count = COUNTER_ATOMIC_INIT(0);
 static struct dentry *deferred_devices;
 static bool initcalls_done;
 
@@ -173,7 +174,7 @@ 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);
+	counter_atomic_inc(&deferred_trigger_count);
 	list_splice_tail_init(&deferred_probe_pending_list,
 			      &deferred_probe_active_list);
 	mutex_unlock(&deferred_probe_mutex);
@@ -466,7 +467,7 @@ int device_bind_driver(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(device_bind_driver);
 
-static atomic_t probe_count = ATOMIC_INIT(0);
+static struct counter_atomic probe_count = COUNTER_ATOMIC_INIT(0);
 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 
 static void driver_deferred_probe_add_trigger(struct device *dev,
@@ -474,7 +475,7 @@ static void driver_deferred_probe_add_trigger(struct device *dev,
 {
 	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_trigger_count != counter_atomic_read(&deferred_trigger_count))
 		driver_deferred_probe_trigger();
 }
 
@@ -493,7 +494,7 @@ static DEVICE_ATTR_RO(state_synced);
 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_trigger_count = counter_atomic_read(&deferred_trigger_count);
 	bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 			   !drv->suppress_bind_attrs;
 
@@ -514,7 +515,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 	if (ret)
 		return ret;
 
-	atomic_inc(&probe_count);
+	counter_atomic_inc(&probe_count);
 	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 		 drv->bus->name, __func__, drv->name, dev_name(dev));
 	if (!list_empty(&dev->devres_head)) {
@@ -648,7 +649,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 	 */
 	ret = 0;
 done:
-	atomic_dec(&probe_count);
+	counter_atomic_dec(&probe_count);
 	wake_up_all(&probe_waitqueue);
 	return ret;
 }
@@ -678,7 +679,7 @@ static int really_probe_debug(struct device *dev, struct device_driver *drv)
  */
 int driver_probe_done(void)
 {
-	int local_probe_count = atomic_read(&probe_count);
+	int local_probe_count = counter_atomic_read(&probe_count);
 
 	pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
 	if (local_probe_count)
@@ -699,7 +700,7 @@ void wait_for_device_probe(void)
 	flush_work(&deferred_probe_work);
 
 	/* wait for the known devices to complete their probing */
-	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
+	wait_event(probe_waitqueue, counter_atomic_read(&probe_count) == 0);
 	async_synchronize_full();
 }
 EXPORT_SYMBOL_GPL(wait_for_device_probe);
-- 
2.25.1