linux-kernel - Re: [PATCH RESEND] tty/sysrq: Do not call sync directly from sysrq_do

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Message-ID: <20181127101135.GA15856@kroah.com>
Date:   Tue, 27 Nov 2018 11:11:35 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mark Tomlinson <mark.tomlinson@...iedtelesis.co.nz>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] tty/sysrq: Do not call sync directly from
 sysrq_do_reset()

On Tue, Nov 27, 2018 at 09:57:23AM +1300, Mark Tomlinson wrote:
> sysrq_do_reset() is called in softirq context, so it cannot call
> sync() directly. Instead, call orderly_reboot(), which creates a work
> item to run /sbin/reboot, or do emergency_sync and restart if the
> command fails.
> 
> Signed-off-by: Mark Tomlinson <mark.tomlinson@...iedtelesis.co.nz>
> ---
>  drivers/tty/sysrq.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index ad1ee5d01b53..f2ca32c1ad7c 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -660,8 +660,7 @@ static void sysrq_do_reset(struct timer_list *t)
>  
>  	state->reset_requested = true;
>  
> -	ksys_sync();
> -	kernel_restart(NULL);
> +	orderly_reboot();

Is this something new?  Why haven't we had reports of this failing in
the past?  Or has something changed recently to cause this to now be
needed?

thanks,

greg k-h