From: Finn Thain <fthain@telegraphics.com.au>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: "Peter Zijlstra" <peterz@infradead.org>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Ingo Molnar" <mingo@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Will Deacon" <will.deacon@arm.com>,
"Paul McKenney" <paulmck@linux.vnet.ibm.com>,
boqun.feng@gmail.com, waiman.long@hpe.com,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"linux-kernel\\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux-Arch <linux-arch@vger.kernel.org>,
"Richard Henderson" <rth@twiddle.net>,
"Vineet Gupta" <vgupta@synopsys.com>,
"Russell King" <linux@arm.linux.org.uk>,
"Hans-Christian Noren Egtvedt" <egtvedt@samfundet.no>,
"Miao Steven" <realmz6@gmail.com>,
"Yoshinori Sato" <ysato@users.sourceforge.jp>,
"Richard Kuo" <rkuo@codeaurora.org>,
"Tony Luck" <tony.luck@intel.com>,
"James Hogan" <james.hogan@imgtec.com>,
"Ralf Baechle" <ralf@linux-mips.org>,
"David Howells" <dhowells@redhat.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Martin Schwidefsky" <schwidefsky@de.ibm.com>,
"Rich Felker" <dalias@libc.org>,
"David S. Miller" <davem@davemloft.net>,
cmetcalf@mellanox.com, "Max Filippov" <jcmvbkbc@gmail.com>,
"Arnd Bergmann" <arnd@arndb.de>,
dbueso@suse.de, "Wu Fengguang" <fengguang.wu@intel.com>,
linux-m68k <linux-m68k@vger.kernel.org>
Subject: Re: [PATCH -v2 14/33] locking,m68k: Implement atomic_fetch_{add,sub,and,or,xor}()
Date: Tue, 21 Jun 2016 14:27:22 +1000 (AEST) [thread overview]
Message-ID: <alpine.LNX.2.00.1606211350360.26385@nippy.intranet> (raw)
In-Reply-To: <87twgniwh7.fsf@linux-m68k.org>
On Mon, 20 Jun 2016, Andreas Schwab wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > Could either of you comment on the below patch?
> >
> > All atomic functions that return a value should imply full memory
> > barrier semantics -- this very much includes a compiler barrier /
> > memory clobber.
>
> I wonder if it is possible to find a case where this makes a real
> difference, ie. where the compiler erroneously reused a value due to the
> missing barrier.
What the compiler does erroneously is a compiler bug by definition. But I
think that was not what you meant.
Perhaps you're asking whether gcc in particular does what you expect,
despite ambiguous source code. But what about other tools like static
analyzers?
Ambiguous code is likely to attract patches like this for as long as it
remains ambiguous. That's a waste of everyone's time, if patches like this
could be written and reviewed just once.
--
>
> Andreas.
>
>
next prev parent reply other threads:[~2016-06-21 4:35 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-31 10:19 [PATCH -v2 00/33] implement atomic_fetch_$op Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 01/33] locking,alpha: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 02/33] locking,arc: Implement atomic_fetch_{add,sub,and,andnot,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 03/33] locking,arm: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 04/33] locking,arm64: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 05/33] arm64: atomic: generate LSE non-return cases using common macros Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 06/33] locking,arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() for LSE instructions Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 07/33] locking,avr32: Implement atomic_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 08/33] locking,blackfin: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 09/33] locking,frv: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 10/33] locking,h8300: Implement atomic_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 11/33] locking,hexagon: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 12/33] locking,ia64: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 13/33] locking,m32r: Implement atomic_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 14/33] locking,m68k: " Peter Zijlstra
2016-06-16 10:08 ` Geert Uytterhoeven
2016-06-16 10:13 ` Peter Zijlstra
2016-06-16 12:43 ` Andreas Schwab
2016-06-16 12:49 ` Peter Zijlstra
2016-06-16 12:53 ` Andreas Schwab
2016-06-16 14:35 ` Peter Zijlstra
2016-06-16 14:37 ` Andreas Schwab
2016-06-16 14:56 ` Peter Zijlstra
2016-06-16 15:04 ` Andreas Schwab
2016-06-16 17:44 ` Peter Zijlstra
2016-06-16 19:18 ` Andreas Schwab
2016-06-16 19:55 ` Geert Uytterhoeven
2016-06-17 15:40 ` Peter Zijlstra
2016-06-20 17:47 ` Andreas Schwab
2016-06-21 4:27 ` Finn Thain [this message]
2016-05-31 10:19 ` [PATCH -v2 15/33] locking,metag: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 16/33] locking,mips: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 17/33] locking,mn10300: Implement atomic_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 18/33] locking,parisc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 19/33] locking,powerpc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}{,_relaxed,_acquire,_release}() Peter Zijlstra
2016-06-01 3:11 ` Boqun Feng
2016-06-01 6:10 ` Boqun Feng
2016-06-01 8:46 ` Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 20/33] locking,s390: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 21/33] locking,sh: Implement atomic_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 22/33] locking,sparc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 17:50 ` David Miller
2016-05-31 10:19 ` [PATCH -v2 23/33] locking,tile: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 24/33] locking,x86: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 25/33] locking,xtensa: Implement atomic_fetch_{add,sub,and,or,xor}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 26/33] locking: Fix atomic64_relaxed bits Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 27/33] locking: Implement atomic{,64,_long}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 28/33] locking: Remove linux/atomic.h:atomic_fetch_or Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 29/33] locking: Remove the deprecated atomic_{set,clear}_mask() functions Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 30/33] locking,alpha: Convert to _relaxed atomics Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 31/33] locking,mips: " Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 32/33] locking,qrwlock: Employ atomic_fetch_add_acquire() Peter Zijlstra
2016-05-31 10:19 ` [PATCH -v2 33/33] locking,rwsem: Employ atomic_long_fetch_add() Peter Zijlstra
2016-06-01 14:06 ` [PATCH -v2 00/33] implement atomic_fetch_$op Will Deacon
2016-06-02 9:27 ` Vineet Gupta
2016-06-02 9:33 ` Peter Zijlstra
2016-06-08 12:43 ` Peter Zijlstra
2016-06-08 12:55 ` Ingo Molnar
2016-06-08 13:32 ` Peter Zijlstra
2016-06-08 14:24 ` Vineet Gupta
2016-06-08 14:38 ` Peter Zijlstra
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