linux-kernel - Re: [PATCH] pstore: avoid recursive spinlocks in the oops_in

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Message-ID: <20120920225727.GD29721@lizard>
Date:	Thu, 20 Sep 2012 15:57:28 -0700
From:	Anton Vorontsov <anton.vorontsov@...aro.org>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
Cc:	gregkh@...uxfoundation.org, keescook@...omium.org,
	tony.luck@...el.com, linux-kernel@...r.kernel.org,
	Colin Cross <ccross@...roid.com>
Subject: Re: [PATCH] pstore: avoid recursive spinlocks in the
 oops_in_progress case

On Tue, Sep 18, 2012 at 01:43:44AM +0800, Chuansheng Liu wrote:
> Like 8250 driver, when pstore is registered as a console,
> to avoid recursive spinlocks when panic happening, change the
> spin_lock_irqsave to spin_trylock_irqsave when oops_in_progress
> is true.
> 
> Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
> ---
>  fs/pstore/platform.c |    7 ++++++-
>  1 files changed, 6 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index 29996e8..cbcb5fc 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -164,7 +164,12 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
>  
>  		if (c > psinfo->bufsize)
>  			c = psinfo->bufsize;
> -		spin_lock_irqsave(&psinfo->buf_lock, flags);
> +
> +		if (oops_in_progress) {
> +			if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
> +				break;

Mm... why break?

Like 8250, in this case it's better still log the console.
That is, something along these lines:

bool locked = 1;

if (oops_in_progress)
	locked = spin_trylock_irqsave(&psinfo->buf_lock, flags);
else
	spin_lock_irqsave(&psinfo->buf_lock, flags);

memcpy(psinfo->buf, s, c);
psinfo->write(PSTORE_TYPE_CONSOLE, 0, NULL, 0, c, psinfo);

if (locked)
	spin_unlock_irqrestore(&psinfo->buf_lock, flags);


Thanks,

Anton.

> +		} else
> +			spin_lock_irqsave(&psinfo->buf_lock, flags);
>  		memcpy(psinfo->buf, s, c);
>  		psinfo->write(PSTORE_TYPE_CONSOLE, 0, NULL, 0, c, psinfo);
>  		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
> -- 
> 1.7.0.4
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