linux-kernel - [PATCH 3/3] staging/android: simplify handle_vsoc_cond

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Message-ID: <f258c416123048ef9eb78baa8ee891b8aa4f6955.1548998323.git.hle@owl.eu.com>
Date:   Fri, 1 Feb 2019 06:39:03 +0100
From:   Hugo Lefeuvre <hle@....eu.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Greg Hartman <ghartman@...gle.com>,
        Alistair Strachan <strachan@...gle.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Christian Brauner <christian@...uner.io>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Joel Fernandes <joel@...lfernandes.org>
Subject: [PATCH 3/3] staging/android: simplify handle_vsoc_cond_wait

simplify handle_vsoc_cond_wait (drivers/staging/android/vsoc.c) using newly
added wait_event_freezable_hrtimeout helper and remove useless includes.

Signed-off-by: Hugo Lefeuvre <hle@....eu.com>
---
 drivers/staging/android/vsoc.c | 69 +++++-----------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/drivers/staging/android/vsoc.c b/drivers/staging/android/vsoc.c
index 22571abcaa4e..7e620e69f39d 100644
--- a/drivers/staging/android/vsoc.c
+++ b/drivers/staging/android/vsoc.c
@@ -17,7 +17,6 @@
  */
 
 #include <linux/dma-mapping.h>
-#include <linux/freezer.h>
 #include <linux/futex.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -29,7 +28,6 @@
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include <linux/interrupt.h>
-#include <linux/mutex.h>
 #include <linux/cdev.h>
 #include <linux/file.h>
 #include "uapi/vsoc_shm.h"
@@ -401,7 +399,6 @@ static int handle_vsoc_cond_wait(struct file *filp, struct vsoc_cond_wait *arg)
 	DEFINE_WAIT(wait);
 	u32 region_number = iminor(file_inode(filp));
 	struct vsoc_region_data *data = vsoc_dev.regions_data + region_number;
-	struct hrtimer_sleeper timeout, *to = NULL;
 	int ret = 0;
 	struct vsoc_device_region *region_p = vsoc_region_from_filep(filp);
 	atomic_t *address = NULL;
@@ -420,69 +417,23 @@ static int handle_vsoc_cond_wait(struct file *filp, struct vsoc_cond_wait *arg)
 	/* Ensure that the type of wait is valid */
 	switch (arg->wait_type) {
 	case VSOC_WAIT_IF_EQUAL:
+		ret = wait_event_freezable(data->futex_wait_queue,
+					   arg->wakes++ &&
+					   atomic_read(address) != arg->value);
 		break;
 	case VSOC_WAIT_IF_EQUAL_TIMEOUT:
-		to = &timeout;
-		break;
-	default:
-		return -EINVAL;
-	}
-
-	if (to) {
-		/* Copy the user-supplied timesec into the kernel structure.
-		 * We do things this way to flatten differences between 32 bit
-		 * and 64 bit timespecs.
-		 */
 		if (arg->wake_time_nsec >= NSEC_PER_SEC)
 			return -EINVAL;
 		wake_time = ktime_set(arg->wake_time_sec, arg->wake_time_nsec);
-
-		hrtimer_init_on_stack(&to->timer, CLOCK_MONOTONIC,
-				      HRTIMER_MODE_ABS);
-		hrtimer_set_expires_range_ns(&to->timer, wake_time,
-					     current->timer_slack_ns);
-
-		hrtimer_init_sleeper(to, current);
+		ret = wait_event_freezable_hrtimeout(data->futex_wait_queue,
+						     arg->wakes++ &&
+						     atomic_read(address) != arg->value,
+						     wake_time);
+		break;
+	default:
+		return -EINVAL;
 	}
 
-	while (1) {
-		prepare_to_wait(&data->futex_wait_queue, &wait,
-				TASK_INTERRUPTIBLE);
-		/*
-		 * Check the sentinel value after prepare_to_wait. If the value
-		 * changes after this check the writer will call signal,
-		 * changing the task state from INTERRUPTIBLE to RUNNING. That
-		 * will ensure that schedule() will eventually schedule this
-		 * task.
-		 */
-		if (atomic_read(address) != arg->value) {
-			ret = 0;
-			break;
-		}
-		if (to) {
-			hrtimer_start_expires(&to->timer, HRTIMER_MODE_ABS);
-			if (likely(to->task))
-				freezable_schedule();
-			hrtimer_cancel(&to->timer);
-			if (!to->task) {
-				ret = -ETIMEDOUT;
-				break;
-			}
-		} else {
-			freezable_schedule();
-		}
-		/* Count the number of times that we woke up. This is useful
-		 * for unit testing.
-		 */
-		++arg->wakes;
-		if (signal_pending(current)) {
-			ret = -EINTR;
-			break;
-		}
-	}
-	finish_wait(&data->futex_wait_queue, &wait);
-	if (to)
-		destroy_hrtimer_on_stack(&to->timer);
 	return ret;
 }
 
-- 
2.20.1