From: Peter Zijlstra <peterz@infradead.org>
To: Torsten Duwe <duwe@lst.de>
Cc: Tom Musta <tommusta@gmail.com>,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>,
Scott Wood <scottwood@freescale.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] Convert powerpc simple spinlocks into ticket locks
Date: Fri, 7 Feb 2014 11:36:13 +0100 [thread overview]
Message-ID: <20140207103613.GF5126@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <20140207103139.GP5002@laptop.programming.kicks-ass.net>
> So if you have ll/sc on the whole word concurrent with the half-word
> store, you can loose the half-word store like:
>
> lwarx &tickets
> ... sth &tail
> stwcd &tickets
>
>
> The stwcd will over-write the tail store.
Oh wait, that's stupid, it will invalidate the lock and fail the store
and make it try again, so you could try and combine the load, but you'd
need an extra shift instruction instead of an extra load.
Not sure that's a valid trade-off..
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Torsten Duwe <duwe@lst.de>
Cc: Scott Wood <scottwood@freescale.com>,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>, Tom Musta <tommusta@gmail.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] Convert powerpc simple spinlocks into ticket locks
Date: Fri, 7 Feb 2014 11:36:13 +0100 [thread overview]
Message-ID: <20140207103613.GF5126@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <20140207103139.GP5002@laptop.programming.kicks-ass.net>
> So if you have ll/sc on the whole word concurrent with the half-word
> store, you can loose the half-word store like:
>
> lwarx &tickets
> ... sth &tail
> stwcd &tickets
>
>
> The stwcd will over-write the tail store.
Oh wait, that's stupid, it will invalidate the lock and fail the store
and make it try again, so you could try and combine the load, but you'd
need an extra shift instruction instead of an extra load.
Not sure that's a valid trade-off..
next prev parent reply other threads:[~2014-02-07 10:36 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-06 10:37 [PATCH] Convert powerpc simple spinlocks into ticket locks Torsten Duwe
2014-02-06 10:37 ` Torsten Duwe
2014-02-06 15:53 ` Benjamin Herrenschmidt
2014-02-06 15:53 ` Benjamin Herrenschmidt
2014-02-06 16:38 ` Peter Zijlstra
2014-02-06 16:38 ` Peter Zijlstra
2014-02-06 17:37 ` Torsten Duwe
2014-02-06 17:37 ` Torsten Duwe
2014-02-06 18:08 ` Peter Zijlstra
2014-02-06 18:08 ` Peter Zijlstra
2014-02-06 19:28 ` Tom Musta
2014-02-10 2:54 ` Benjamin Herrenschmidt
2014-02-10 2:54 ` Benjamin Herrenschmidt
2014-02-07 8:24 ` Torsten Duwe
2014-02-07 8:24 ` Torsten Duwe
2014-02-06 20:19 ` Scott Wood
2014-02-06 20:19 ` Scott Wood
2014-02-07 9:02 ` Torsten Duwe
2014-02-07 9:02 ` Torsten Duwe
2014-02-07 10:31 ` Peter Zijlstra
2014-02-07 10:31 ` Peter Zijlstra
2014-02-07 10:36 ` Peter Zijlstra [this message]
2014-02-07 10:36 ` Peter Zijlstra
2014-02-07 10:45 ` Peter Zijlstra
2014-02-07 10:45 ` Peter Zijlstra
2014-02-07 11:49 ` Torsten Duwe
2014-02-07 11:49 ` Torsten Duwe
2014-02-07 12:28 ` Peter Zijlstra
2014-02-07 12:28 ` Peter Zijlstra
2014-02-07 15:18 ` Peter Zijlstra
2014-02-07 15:18 ` Peter Zijlstra
2014-02-07 15:43 ` Peter Zijlstra
2014-02-07 15:43 ` Peter Zijlstra
2014-02-07 17:08 ` Torsten Duwe
2014-02-07 17:08 ` Torsten Duwe
2014-02-07 17:19 ` Peter Zijlstra
2014-02-07 17:19 ` Peter Zijlstra
2014-02-07 15:51 ` Kumar Gala
2014-02-07 15:51 ` Kumar Gala
2014-02-07 16:10 ` Peter Zijlstra
2014-02-07 16:10 ` Peter Zijlstra
2014-02-10 3:05 ` Benjamin Herrenschmidt
2014-02-10 3:05 ` Benjamin Herrenschmidt
2014-02-10 3:02 ` Benjamin Herrenschmidt
2014-02-10 3:02 ` Benjamin Herrenschmidt
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