linux-kernel - Re: [PATCH] Revert "x86/tsc: Consolidate init code"

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Date:   Mon, 10 Sep 2018 17:07:10 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Dou Liyang <douly.fnst@...fujitsu.com>,
        Pavel Tatashin <pasha.tatashin@...rosoft.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] Revert "x86/tsc: Consolidate init code"

On Mon, Sep 10, 2018 at 02:48:45PM +0200, Thomas Gleixner wrote:
> Ville,
> 
> On Mon, 10 Sep 2018, Ville Syrjala wrote:
> 
> > From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> > 
> > This reverts commit 608008a45798fe9e2aee04f99b5270ea57c1376f.
> > 
> > It breaks wifi on my pentium 3 Fujitsu-Siemens Lifebook S6010
> > laptop. Scanning for APs doesn't seem to work most of the time,
> > and, even when it manages to find some APs it never manages to
> > authenticate successfully. dmesg is just littered with:
> > "wlan0: send auth to ... (try 1/3)
> >  wlan0: send auth to ... (try 2/3)
> >  wlan0: send auth to ... (try 3/3)
> >  wlan0: authentication with ... timed out"
> 
> I asked for that before and I really do not understand why you do not even
> make an attempt to report an issue first and allow the developers to work
> with you to figure out what exactly is the problem. All you do is to send
> an revert patch with a changelog which describes symptoms and probably
> breaks more than it cures. Not really helpful, really.

You're reading way too much into this. The revert is just a point to
start the conversion. I've found that it's the best way to get the
attention of the relevant developers. Other kind of regression
reports have an unfortunate habit of disappearing into /dev/null.

> 
> It's surely helpful to know that you bisected it to that commit and
> reverting it helps. Can you please provide more detailes information like
> dmesg of an good and a bad boot?

I think the only real difference (apart from the USB noise) is:
- clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1cbd01c4e18, max_idle_ns: 881590491211 ns
- Calibrating delay loop (skipped), value calculated using timer frequency.. 1718674.70 BogoMIPS (lpj=2863311530)
+ clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1cbc55fe3af, max_idle_ns: 881590592998 ns
+ Calibrating delay loop (skipped), value calculated using timer frequency.. 859455.59 BogoMIPS (lpj=1431852151)

Full logs attached.

-- 
Ville Syrjälä
Intel

View attachment "dmesg.bad" of type "text/plain" (48385 bytes)

View attachment "dmesg.good" of type "text/plain" (46922 bytes)