linux-kernel - RE: [PATCH] kernel: x86: tboot: Replace mdelay with usleep_range in tboot_wait_for

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Date:   Thu, 25 Jan 2018 10:35:17 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Sun, Ning" <ning.sun@...el.com>
cc:     Jia-Ju Bai <baijiaju1990@...il.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "tboot-devel@...ts.sourceforge.net" 
        <tboot-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] kernel: x86: tboot: Replace mdelay with usleep_range in
 tboot_wait_for_aps

On Wed, 24 Jan 2018, Sun, Ning wrote:

Please do NOT top post and do NOT include the whole mail header in your
reply.

> >> The function tboot_wait_for_aps is not called in atomic context.
> >> Thus mdelay can be replaced with usleep_range, to reduce busy wait.
> > And how did you establish that it's not called in atomic context?
> >
> It is reported by a static analysis tool written by myself.  This tool
> finds that mdelay in tboot_wait_for_aps is not called by holding a
> spinlock or in an interrupt handler, thus mdelay can be replaced.

> It looks like tboot_wait_for_aps(...) is not called in atomic context .

You are both failing to look at the calling context of this. Care to follow
the invocation chain and look at the context?

Thanks,

	tglx