From: Peter Zijlstra <peterz@infradead.org>
To: Will Newton <will.newton@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Jason Baron <jbaron@redhat.com>,
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
hpa@zytor.com, mingo@elte.hu, tglx@linutronix.de,
andi@firstfloor.org, roland@redhat.com, rth@redhat.com,
masami.hiramatsu.pt@hitachi.com, fweisbec@gmail.com,
avi@redhat.com, davem@davemloft.net, sam@ravnborg.org,
ddaney@caviumnetworks.com, michael@ellerman.id.au,
linux-kernel@vger.kernel.org, Mike Frysinger <vapier@gentoo.org>,
Chris Metcalf <cmetcalf@tilera.com>,
dhowells <dhowells@redhat.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
"heiko.carstens" <heiko.carstens@de.ibm.com>,
benh <benh@kernel.crashing.org>
Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates
Date: Mon, 14 Feb 2011 19:04:27 +0100 [thread overview]
Message-ID: <1297706667.5226.165.camel@laptop> (raw)
In-Reply-To: <AANLkTi=jz+mGru--+YA62EeER17Tuq2DocrkKNaU2k+1@mail.gmail.com>
On Mon, 2011-02-14 at 17:50 +0000, Will Newton wrote:
> On Mon, Feb 14, 2011 at 5:43 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Mon, 2011-02-14 at 17:38 +0000, Will Newton wrote:
> >> On Mon, Feb 14, 2011 at 5:27 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> >>
> >> >> So all but a few have basically (as you said on IRC)
> >> >> #define atomic_read(v) ACCESS_ONCE(v)
> >> >
> >> > ACCESS_ONCE(v->counter), but yeah :-)
> >>
> >> I maintain an out-of-tree architecture where that isn't the case
> >> unfortunately [1]. Not expecting any special favours for being
> >> out-of-tree of course, but just thought I would add that data point.
> >>
> >> [1] Our atomic operations go around the cache rather than through it,
> >> so the value of an atomic cannot be read with a normal load
> >> instruction.
> >
> > Cannot how? It would observe a stale value? That is acceptable for
> > atomic_read().
>
> It would observe a stale value, but that value would only be updated
> when the cache line was reloaded from main memory which would have to
> be triggered by either eviction or cache flushing. So it could get
> pretty stale. Whilst that's probably within the spec. of atomic_read I
> suspect it would lead to problems in practice. I could be wrong
> though.
Arguable, finding such cases would be a Good (TM) thing.. but yeah, I
can imagine you're not too keen on being the one finding them.
Luckily it looks like you're in the same boat as blackfin-smp is.
next prev parent reply other threads:[~2011-02-14 18:03 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-05 15:43 [PATCH 0/2] jump label: 2.6.38 updates Jason Baron
2011-01-05 15:43 ` [PATCH 1/2] jump label: make enable/disable o(1) Jason Baron
2011-01-05 17:31 ` Steven Rostedt
2011-01-05 21:19 ` Jason Baron
2011-01-05 15:43 ` [PATCH 2/2] jump label: introduce static_branch() Jason Baron
2011-01-05 17:15 ` Frederic Weisbecker
2011-01-05 17:46 ` Steven Rostedt
2011-01-05 18:52 ` H. Peter Anvin
2011-01-05 21:19 ` Jason Baron
2011-01-05 21:14 ` Jason Baron
2011-01-05 17:32 ` David Daney
2011-01-05 17:43 ` Steven Rostedt
2011-01-05 18:44 ` David Miller
2011-01-05 20:04 ` Steven Rostedt
2011-01-05 18:56 ` H. Peter Anvin
2011-01-05 19:14 ` Ingo Molnar
2011-01-05 19:32 ` David Daney
2011-01-05 19:50 ` Ingo Molnar
2011-01-05 20:07 ` David Daney
2011-01-05 20:08 ` H. Peter Anvin
2011-01-05 20:18 ` Ingo Molnar
2011-01-05 21:16 ` Jason Baron
2011-01-05 17:41 ` Steven Rostedt
2011-01-09 18:48 ` Mathieu Desnoyers
2011-02-11 19:25 ` [PATCH 0/2] jump label: 2.6.38 updates Peter Zijlstra
2011-02-11 21:13 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP101B686C32E10BA346B15F896EF0@phx.gbl>
2011-02-11 21:38 ` Peter Zijlstra
2011-02-11 22:15 ` Jason Baron
2011-02-11 22:19 ` H. Peter Anvin
2011-02-11 22:30 ` Mathieu Desnoyers
2011-02-11 22:20 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP8562BA758CF8AAE5323AE296EF0@phx.gbl>
2011-02-11 22:27 ` Jason Baron
2011-02-11 22:32 ` Mathieu Desnoyers
2011-02-12 18:47 ` Peter Zijlstra
2011-02-14 12:27 ` Ingo Molnar
2011-02-14 15:51 ` Jason Baron
2011-02-14 15:57 ` Peter Zijlstra
2011-02-14 16:04 ` Jason Baron
2011-02-14 16:14 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP4069A1A89F06CDFF9B28F896D00@phx.gbl>
2011-02-14 16:25 ` Peter Zijlstra
2011-02-14 16:29 ` Jason Baron
2011-02-14 16:37 ` Peter Zijlstra
2011-02-14 16:43 ` Mathieu Desnoyers
2011-02-14 16:46 ` Steven Rostedt
2011-02-14 16:53 ` Peter Zijlstra
2011-02-14 17:18 ` Steven Rostedt
2011-02-14 17:23 ` Mike Frysinger
2011-02-14 17:27 ` Peter Zijlstra
2011-02-14 17:29 ` Mike Frysinger
2011-02-14 17:38 ` Peter Zijlstra
2011-02-14 17:45 ` Mike Frysinger
2011-02-14 17:38 ` Will Newton
2011-02-14 17:43 ` Peter Zijlstra
2011-02-14 17:50 ` Will Newton
2011-02-14 18:04 ` Peter Zijlstra [this message]
2011-02-14 18:24 ` Peter Zijlstra
2011-02-14 18:53 ` Mathieu Desnoyers
2011-02-14 21:29 ` Steven Rostedt
2011-02-14 21:39 ` Steven Rostedt
2011-02-14 21:46 ` David Miller
2011-02-14 22:20 ` Steven Rostedt
2011-02-14 22:21 ` Steven Rostedt
2011-02-14 22:21 ` H. Peter Anvin
2011-02-14 22:29 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP98BFCC52FD41661DD9CC1E96D00@phx.gbl>
2011-02-14 22:33 ` David Miller
2011-02-14 22:33 ` David Miller
2011-02-14 22:37 ` Matt Fleming
2011-02-14 23:03 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP166A8555C791786059B0FF96D00@phx.gbl>
2011-02-14 23:09 ` Paul E. McKenney
2011-02-14 23:29 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP4599FAAD7330498472B87396D00@phx.gbl>
2011-02-15 0:19 ` Segher Boessenkool
2011-02-15 0:48 ` Mathieu Desnoyers
2011-02-15 1:29 ` Steven Rostedt
[not found] ` <BLU0-SMTP984E876DBDFBC13F4C86F896D00@phx.gbl>
2011-02-15 0:42 ` Paul E. McKenney
2011-02-15 0:51 ` Mathieu Desnoyers
2011-02-15 11:53 ` Will Newton
2011-02-18 19:03 ` Paul E. McKenney
2011-02-14 23:19 ` H. Peter Anvin
2011-02-15 11:01 ` Will Newton
2011-02-15 13:31 ` H. Peter Anvin
2011-02-15 13:49 ` Steven Rostedt
2011-02-15 14:04 ` Will Newton
2011-02-15 21:11 ` Will Simoneau
2011-02-15 21:27 ` David Miller
2011-02-15 21:56 ` Will Simoneau
2011-02-16 10:15 ` Will Newton
2011-02-16 12:18 ` Steven Rostedt
2011-02-16 12:41 ` Will Newton
2011-02-16 13:24 ` Mathieu Desnoyers
2011-02-16 22:51 ` Will Simoneau
2011-02-17 0:53 ` Please watch your cc lists Andi Kleen
2011-02-17 0:56 ` David Miller
2011-02-17 1:04 ` Michael Witten
2011-02-17 10:55 ` [PATCH 0/2] jump label: 2.6.38 updates Will Newton
[not found] ` <BLU0-SMTP80F56386E7E060A3B2020B96D20@phx.gbl>
2011-02-17 1:55 ` Masami Hiramatsu
2011-02-17 3:19 ` H. Peter Anvin
2011-02-17 16:03 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP71BCB155CBAE79997EE08D96D20@phx.gbl>
2011-02-17 3:36 ` Steven Rostedt
2011-02-17 16:13 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP51D40A5B1DACA8883D6AB596D50@phx.gbl>
2011-02-17 20:09 ` Steven Rostedt
2011-02-15 22:20 ` Benjamin Herrenschmidt
2011-02-16 8:35 ` Ingo Molnar
2011-02-17 1:04 ` H. Peter Anvin
2011-02-17 12:51 ` Ingo Molnar
[not found] ` <BLU0-SMTP637B2E9372CFBF3A0B5B0996D00@phx.gbl>
2011-02-14 23:25 ` David Miller
2011-02-14 23:34 ` Mathieu Desnoyers
[not found] ` <20110214233405.GC17432@Krystal>
2011-02-14 23:52 ` Mathieu Desnoyers
2011-02-14 22:15 ` Matt Fleming
2011-02-15 15:20 ` Heiko Carstens
[not found] ` <BLU0-SMTP64371A838030ED92A7CCB696D00@phx.gbl>
2011-02-14 18:54 ` Jason Baron
2011-02-14 19:20 ` Peter Zijlstra
2011-02-14 19:48 ` Mathieu Desnoyers
2011-02-14 16:11 ` Mathieu Desnoyers
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