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From: Mike Galbraith <gleep@gmx.de>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] x86: UV: raw_spinlock conversion
Date: Tue, 22 May 2018 10:24:22 +0200	[thread overview]
Message-ID: <1526977462.6491.1.camel@gmx.de> (raw)
In-Reply-To: <20180522065051.xy42nwvcxz2nekti@linutronix.de>

On Tue, 2018-05-22 at 08:50 +0200, Sebastian Andrzej Siewior wrote:
> 
> Regarding the preempt_disable() in the original patch in uv_read_rtc():
> This looks essential for PREEMPT configs. Is it possible to get this
> tested by someone or else get rid of the UV code? It looks broken for
> "uv_get_min_hub_revision_id() != 1".

I suspect SGI cares not one whit about PREEMPT.

> Why does PREEMPT_RT require migrate_disable() but PREEMPT only is fine
> as-is? This does not look right.

UV is not ok with a PREEMPT config, it's just that for RT it's dirt
simple to shut it up, whereas for PREEMPT, preempt_disable() across
uv_bau_init() doesn't cut it due to allocations, and whatever else I
would have met before ending the whack-a-mole game.

If I were in your shoes, I think I'd just stop caring about UV until a
real user appears.  AFAIK, I'm the only guy who ever ran RT on UV, and
I only did so because SUSE asked me to look into it.. years ago now.

	-Mike

  reply	other threads:[~2018-05-22  8:24 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-04 11:14 [PATCH] x86: Convert mce timer to hrtimer Sebastian Andrzej Siewior
2018-05-04 11:14 ` Sebastian Andrzej Siewior
2018-05-04 11:14 ` [PATCH] x86: UV: raw_spinlock conversion Sebastian Andrzej Siewior
2018-05-06 10:26   ` Thomas Gleixner
2018-05-06 10:59     ` Mike Galbraith
2018-05-07  7:39       ` Sebastian Andrzej Siewior
2018-05-07  7:59         ` Mike Galbraith
2018-05-19 14:09         ` Mike Galbraith
2018-05-22  6:50           ` Sebastian Andrzej Siewior
2018-05-22  8:24             ` Mike Galbraith [this message]
2018-05-22  9:14               ` Sebastian Andrzej Siewior
2018-05-22  9:46                 ` Mike Galbraith
2018-05-22 12:48                   ` Mike Galbraith
2018-05-07  9:04 ` [PATCH] x86: Convert mce timer to hrtimer Sebastian Andrzej Siewior
2018-05-07  9:04   ` Sebastian Andrzej Siewior

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