Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 26 Feb 2020 13:59:28 -0800
From:   Andi Kleen <ak@linux.intel.com>
To:     "Luck, Tony" <tony.luck@intel.com>
Cc:     Kyung Min Park <kyung.min.park@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com, gregkh@linuxfoundation.org, ashok.raj@intel.com,
        ravi.v.shankar@intel.com, fenghua.yu@intel.com
Subject: Re: [PATCH 2/2] x86/asm/delay: Introduce TPAUSE delay
Message-ID: <20200226215928.GU160988@tassilo.jf.intel.com>
References: <1582744258-42744-1-git-send-email-kyung.min.park@intel.com>
 <1582744258-42744-3-git-send-email-kyung.min.park@intel.com>
 <20200226211040.GS160988@tassilo.jf.intel.com>
 <20200226212034.GA21102@agluck-desk2.amr.corp.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200226212034.GA21102@agluck-desk2.amr.corp.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Feb 26, 2020 at 01:20:34PM -0800, Luck, Tony wrote:
> On Wed, Feb 26, 2020 at 01:10:40PM -0800, Andi Kleen wrote:
> > On Wed, Feb 26, 2020 at 11:10:58AM -0800, Kyung Min Park wrote:
> > > TPAUSE instructs the processor to enter an implementation-dependent
> > > optimized state. The instruction execution wakes up when the time-stamp
> > > counter reaches or exceeds the implicit EDX:EAX 64-bit input value.
> > > The instruction execution also wakes up due to the expiration of
> > > the operating system time-limit or by an external interrupt
> > 
> > This is actually a behavior change. Today's udelay() will continue
> > after processing the interrupt. Your patches don't
> 
> The instruction level TPAUSE is called inside delay_wait()
> that checks to see of we were interrupted early and loops to issue
> another TPAUSE if needed.

Ah right. It was already solved for mwaitx. Great.

-Andi