linux-kernel - Re: [PATCH 3/5] logger: reorder prepare_to_wait and mutex

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Message-ID: <CAPz4a6DiPaSAF3ZhmnTDnjwXHXv0at32QTMmRrgP8VyLOSG_Ug@mail.gmail.com>
Date:	Wed, 8 Feb 2012 21:56:54 -0800
From:	Dima Zavin <dima@...roid.com>
To:	Tim Bird <tim.bird@...sony.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	linux-embedded <linux-embedded@...r.kernel.org>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH 3/5] logger: reorder prepare_to_wait and mutex_lock

On Tue, Feb 7, 2012 at 6:30 PM, Tim Bird <tim.bird@...sony.com> wrote:
> If mutex_lock waits, it will return in state TASK_RUNNING,
> rubbing out the effect of prepare_to_wait().
>
> Signed-off-by: Tim Bird <tim.bird@...sony.com>

Acked-by: Dima Zavin <dima@...roid.com>

> ---
>  drivers/staging/android/logger.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c
> index 92cfd94..54b7cdf 100644
> --- a/drivers/staging/android/logger.c
> +++ b/drivers/staging/android/logger.c
> @@ -172,9 +172,10 @@ static ssize_t logger_read(struct file *file, char __user *buf,
>
>  start:
>        while (1) {
> +               mutex_lock(&log->mutex);
> +
>                prepare_to_wait(&log->wq, &wait, TASK_INTERRUPTIBLE);
>
> -               mutex_lock(&log->mutex);
>                ret = (log->w_off == reader->r_off);
>                mutex_unlock(&log->mutex);
>                if (!ret)
> --
> 1.7.2.3
>
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