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

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Message-ID: <20190204155213.GA41502@google.com>
Date:   Mon, 4 Feb 2019 10:52:13 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Hugo Lefeuvre <hle@....eu.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Greg Hartman <ghartman@...gle.com>,
        Alistair Strachan <astrachan@...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
Subject: Re: [PATCH 3/3] staging/android: simplify handle_vsoc_cond_wait

I think you sent to wrong address of Alistair on these and other patches. Corrected address.

On Fri, Feb 01, 2019 at 06:39:03AM +0100, Hugo Lefeuvre wrote:
> 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