From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 3/4] sparc64: convert spinlock_t to raw_spinlock_t in
 mmu_context_t
Date: Tue, 04 Mar 2014 23:52:07 -0500 (EST)
Message-ID: <20140304.235207.1428291234888893240.davem@davemloft.net>
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Cc: tkhai@yandex.ru, linux-rt-users@vger.kernel.org,
	sparclinux@vger.kernel.org, bigeasy@linutronix.de
To: allen.pais@oracle.com
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From: Allen Pais <allen.pais@oracle.com>
Date: Wed, 05 Mar 2014 10:04:56 +0530

> On Wednesday 05 March 2014 01:31 AM, David Miller wrote:
>> From: Allen Pais <allen.pais@oracle.com>
>> Date: Wed, 19 Feb 2014 09:23:46 +0530
>> 
>>>  I realized locking in tsb is very tricky. My attempts to try and get hackbench run
>>> without causing a stall failed. So here's what I tried to fix it, am not sure if it's
>>> an appropriate fix, I would love to get comments. I have tested this fix for over 24 hours
>>> with hackbench and dd, the system did not stall :)
>> 
>> If using a local lock fixes your problem, it just means we're being
>> preempted during flush_tsb_user() which is absolutely not allowed.
> 
> David, Its my bad, I realized my mistake of using local locks.
> Am still looking into the tsb flush code. It's left me sleepless. :)

So let's do a simple test, in flush_tlb_user() assert to make sure we
cannot be preempted by the -rt kernel.