linux-kernel - Re: [PATCH RESEND] rtsx_usb_ms: Use msleep

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Message-ID: <20160503134009.GA26668@redhat.com>
Date:	Tue, 3 May 2016 15:40:09 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Oleksandr Natalenko <oleksandr@...alenko.name>,
	Ben Hutchings <ben@...adent.org.uk>,
	Lee Jones <lee.jones@...aro.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Roger Tseng <rogerable@...ltek.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] rtsx_usb_ms: Use msleep_interruptible() in
 polling loop

On 05/02, Andrew Morton wrote:
>
> On Mon, 02 May 2016 23:17:41 +0300 Oleksandr Natalenko <oleksandr@...alenko.name> wrote:
>
> > rtsx_usb_ms creates a task that mostly sleeps, but tasks in
> > uninterruptible sleep still contribute to the load average (for
> > bug-compatibility with Unix).

We have TASK_NOLOAD/TASK_IDLE, you can just use schedule_timeout_idle(HZ).

but msleep_interruptible(1000) is fine too.

> > --- a/drivers/memstick/host/rtsx_usb_ms.c
> > +++ b/drivers/memstick/host/rtsx_usb_ms.c
> > @@ -706,7 +706,8 @@ poll_again:
> >   		if (host->eject)
> >   			break;
> >
> > -		msleep(1000);
> > +		if (msleep_interruptible(1000))
> > +			flush_signals(current);
> >   	}
> >
> >   	complete(&host->detect_ms_exit);
>
> flush_signals() is a bit scary.
...
> But this isn't a userspace task - it's a kthread.  So I don't *think*
> it can get any signals anyway?

Agreed, it is not needed and only adds some confusion, so I think
rtsx_usb_ms-use-msleep_interruptible-in-polling-loop.patch should be
updated.

A kernel thread ignores all signals unless it does allow_signal(), so
you can safely remove flush_signals().

Oleg.