From: Andi Kleen <andi@firstfloor.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>,
Waiman Long <Waiman.Long@hp.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Arnd Bergmann <arnd@arndb.de>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michel Lespinasse <walken@google.com>,
Rik van Riel <riel@redhat.com>,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
George Spelvin <linux@horizon.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Aswin Chandramouleeswaran <aswin@hp.com>,
Scott J Norton <scott.norton@hp.com>
Subject: Re: [PATCH v7 1/4] qrwlock: A queue read/write lock implementation
Date: Wed, 18 Dec 2013 11:38:29 -0800 [thread overview]
Message-ID: <878uvilzka.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <CA+55aFzNSZCKnuEm+CDWUN2G4bfrN+HafX8r13NcfT2tJ4h-jw@mail.gmail.com> (Linus Torvalds's message of "Tue, 17 Dec 2013 11:27:29 -0800")
Linus Torvalds <torvalds@linux-foundation.org> writes:
>
> In this case, we seem to want the xadd() semantics. I guess we can use
> "atomic_add_return(val,&atomic)-val" and just assume that the compiler
> gets it right (with the addition and the subtraction cancelling out).
It can't, as we use inline assembler.
In theory it could with __sync_* or __atomic_* intrinsics but we
traditionally don't use them as they don't support patchable LOCK
(maybe it would be time to get rid of the patchable LOCK though?)
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2013-12-18 19:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-22 19:04 [PATCH v7 0/4] qrwlock: Introducing a queue read/write lock implementation Waiman Long
2013-11-22 19:04 ` [PATCH v7 1/4] qrwlock: A " Waiman Long
2013-11-22 19:14 ` Linus Torvalds
2013-11-22 20:35 ` Waiman Long
2013-11-22 21:14 ` Linus Torvalds
2013-12-17 19:21 ` Paul E. McKenney
2013-12-17 19:27 ` Linus Torvalds
2013-12-17 19:49 ` Paul E. McKenney
2013-12-18 18:51 ` Waiman Long
2013-12-18 19:38 ` Andi Kleen [this message]
2013-12-18 19:42 ` Andi Kleen
2013-12-18 19:46 ` Peter Zijlstra
2013-12-18 20:16 ` Andi Kleen
2013-12-18 18:45 ` Waiman Long
2013-12-18 18:45 ` Waiman Long
2013-12-18 18:59 ` Paul E. McKenney
2013-12-18 18:59 ` Paul E. McKenney
2013-12-18 19:16 ` Peter Zijlstra
2013-12-18 19:16 ` Peter Zijlstra
2013-11-22 19:04 ` [PATCH v7 2/4] qrwlock x86: Enable x86 to use queue read/write lock Waiman Long
2013-11-22 19:04 ` Waiman Long
2013-12-17 19:22 ` Paul E. McKenney
2013-11-22 19:04 ` [PATCH v7 3/4] qrwlock: Use the mcs_spinlock helper functions for MCS queuing Waiman Long
2013-12-17 19:23 ` Paul E. McKenney
2013-11-22 19:04 ` [PATCH v7 4/4] qrwlock: Use smp_store_release() in write_unlock() Waiman Long
2013-12-17 19:24 ` Paul E. McKenney
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