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Date:   Mon, 8 Apr 2019 19:02:47 -0700
From:   Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@suse.de>,
        Ashok Raj <ashok.raj@intel.com>,
        Andi Kleen <andi.kleen@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        Ricardo Neri <ricardo.neri@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Tony Luck <tony.luck@intel.com>,
        Clemens Ladisch <clemens@ladisch.de>,
        Arnd Bergmann <arnd@arndb.de>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Jan Kiszka <jan.kiszka@siemens.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Nayna Jain <nayna@linux.ibm.com>
Subject: Re: [RFC PATCH v2 12/14] x86/watchdog/hardlockup/hpet: Determine if
 HPET timer caused NMI
Message-ID: <20190409020247.GA7008@ranerica-svr.sc.intel.com>
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On Tue, Mar 26, 2019 at 09:55:35PM +0100, Thomas Gleixner wrote:
> On Wed, 27 Feb 2019, Ricardo Neri wrote:
> > @@ -62,7 +67,18 @@ static inline void set_comparator(struct hpet_hld_data *hdata,
> >  static void kick_timer(struct hpet_hld_data *hdata, bool force)
> >  {
> >  	bool kick_needed = force || !(hdata->flags & HPET_DEV_PERI_CAP);
> > -	unsigned long new_compare, count;
> > +	unsigned long tsc_curr, tsc_delta, new_compare, count;
> > +
> > +	/* Start obtaining the current TSC and HPET counts. */
> > +	tsc_curr = rdtsc();
> > +
> > +	if (kick_needed)
> > +		count = get_count();
> 
> Can you please keep the TSC code in one block and the HPET block in the
> next one? Having this inbetween is really bad to follow.
> 
> It really does not matter whether you read the HPET counter before or after
> the calculation. This is a crystal ball estimation anyway so a few cyles
> more or less are completely irrelevant.

Sure! I will implement this change.

Thanks and BR,
Ricardo

> 
> > +	tsc_delta = (unsigned long)watchdog_thresh * (unsigned long)tsc_khz
> > +		    * 1000L;
> > +	hdata->tsc_next = tsc_curr + tsc_delta;
> > +	hdata->tsc_next_error = tsc_delta >> 6;
> 
> Thanks,
> 
> 	tglx