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Date: Thu, 6 Sep 2018 23:10:39 +1000
From: Nicholas Piggin <npiggin@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>, Michael Ellerman <mpe@ellerman.id.au>,
 Matteo Croce <mcroce@redhat.com>, Jason Gunthorpe <jgg@mellanox.com>, Leon
 Romanovsky <leonro@mellanox.com>, linuxppc-dev@lists.ozlabs.org,
 linux-kernel@vger.kernel.org (op)
Subject: Re: [PATCH 3/3] tty: hvc: hvc_write() fix break condition
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On Wed,  5 Sep 2018 22:14:39 +1000
Nicholas Piggin <npiggin@gmail.com> wrote:

> Commit 550ddadcc758 ("tty: hvc: hvc_write() may sleep") broke the
> termination condition in case the driver stops accepting characters.
> This can result in unnecessary polling of the busy driver.
> 
> Restore it by testing the hvc_push return code.
> 
> Fixes: 550ddadcc758 ("tty: hvc: hvc_write() may sleep")
> Tested-by: Matteo Croce <mcroce@redhat.com>
> Tested-by: Leon Romanovsky <leonro@mellanox.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  drivers/tty/hvc/hvc_console.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
> index bacf9b73ec98..c09a38fb0d66 100644
> --- a/drivers/tty/hvc/hvc_console.c
> +++ b/drivers/tty/hvc/hvc_console.c
> @@ -522,6 +522,8 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count
>  		return -EIO;
>  
>  	while (count > 0) {
> +		int ret;
> +
>  		spin_lock_irqsave(&hp->lock, flags);
>  
>  		rsize = hp->outbuf_size - hp->n_outbuf;

That needs to be 'int ret = 0;' to avoid used uninitialized.

Let me know if I should resend the patches.

Thanks,
Nick