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From: Thomas Gleixner <tglx@linutronix.de>
To: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: "Li, Aubrey" <aubrey.li@linux.intel.com>,
	Daniel Drake <drake@endlessm.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Endless Linux Upstreaming Team <linux@endlessm.com>,
	Jiri Slaby <jslaby@suse.cz>
Subject: Re: [PATCH] x86/apic: Handle missing global clockevent gracefully
Date: Fri, 9 Aug 2019 21:40:26 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1908092138520.21433@nanos.tec.linutronix.de> (raw)
In-Reply-To: <d212566c-3ee6-a7c1-98f5-2db5d3c63e44@amd.com>

On Fri, 9 Aug 2019, Lendacky, Thomas wrote:
> On 8/9/19 7:54 AM, Thomas Gleixner wrote:
> > +	local_irq_disable();
> >   	/*
> >   	 * Setup the APIC counter to maximum. There is no way the lapic
> >   	 * can underflow in the 100ms detection time frame
> >   	 */
> >   	__setup_APIC_LVTT(0xffffffff, 0, 0);
> >   
> > -	/* Let the interrupts run */
> > -	local_irq_enable();
> > +	/*
> > +	 * Methods to terminate the calibration loop:
> > +	 *  1) Global clockevent if available (jiffies)
> > +	 *  2) TSC if available and frequency is known
> > +	 */
> > +	jif_start = READ_ONCE(jiffies);
> > +
> > +	if (tsc_khz) {
> > +		tsc_start = rdtsc();
> > +		tsc_perj = div_u64((u64)tsc_khz * 1000, HZ);
> > +	}
> > +
> > +	while (lapic_cal_loops <= LAPIC_CAL_LOOPS) {
> > +		/*
> > +		 * Enable interrupts so the tick can fire, if a global
> > +		 * clockevent device is available
> > +		 */
> > +		local_irq_enable();
> 
> Just a nit, but you end up doing this at the bottom of the loop, so you
> could move this invocation to just before the loop and avoid doing two
> local_irq_enable() calls in succession after the first iteration.

Indeed. Lets see how the reports go. That change is a nobrainer.

Thanks,

	tglx

  reply	other threads:[~2019-08-09 19:40 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01  6:24 setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01  7:16 ` Aubrey Li
2019-08-01  7:35   ` Thomas Gleixner
2019-08-01  7:56     ` Aubrey Li
2019-08-01  8:13       ` Thomas Gleixner
2019-08-01  8:21         ` Li, Aubrey
2019-08-01 10:13           ` Thomas Gleixner
2019-08-01 15:44             ` Lendacky, Thomas
2019-08-08 20:36               ` Thomas Gleixner
2019-08-08 21:01                 ` Lendacky, Thomas
2019-08-08 21:08                   ` Thomas Gleixner
2019-08-08 21:36                     ` Lendacky, Thomas
2019-08-09 12:54                       ` [PATCH] x86/apic: Handle missing global clockevent gracefully Thomas Gleixner
2019-08-09 12:59                         ` Jiri Slaby
2019-08-09 13:58                         ` Lendacky, Thomas
2019-08-09 19:40                           ` Thomas Gleixner [this message]
2019-08-12  6:16                         ` Daniel Drake
2019-08-12  7:03                           ` Jiri Slaby
2019-08-15  5:02                           ` Daniel Drake
2019-08-12  7:46                         ` Li, Aubrey
2019-08-12 12:24                           ` Thomas Gleixner
2019-08-12 12:59                             ` Aubrey Li
2019-08-12 17:11                               ` Thomas Gleixner
2019-08-19 10:37                         ` [tip:x86/urgent] " tip-bot for Thomas Gleixner
2019-08-01  9:00   ` setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01 10:17     ` Thomas Gleixner
2019-08-01  7:27 ` Thomas Gleixner

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