From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Dmitry Vyukov <dvyukov@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH RFC] locking: Add volatile to arch_spinlock_t structures
Date: Thu, 4 Dec 2014 14:06:57 -0800 [thread overview]
Message-ID: <20141204220657.GB25340@linux.vnet.ibm.com> (raw)
In-Reply-To: <20141204214546.76b7b7cd@lxorguk.ukuu.org.uk>
On Thu, Dec 04, 2014 at 09:45:46PM +0000, One Thousand Gnomes wrote:
> > anywhere in that translation unit. After all, any non-static function
> > in that translation unit might be called from some other translation
> > unit that -did- use locking or whatever.
> >
> > I will let you know how it goes. ;-)
>
> It breaks DEC10 ;-)
To say nothing of CDC 6600 systems lacking the compare-move unit. ;-)
> If there is kickback over things like optimisation perhaps the gcc
> maintainers could at least consider something like
>
> int __attribute((threadsafe)) fred;
>
> ??
Not needed for recent gcc versions -- both the C11 and C++11 standards
require that different threads be permitted to independently access
different variables, where "different" means "no bits of the two variables
residing in the same byte". From what I can see, this would mean that
a conforming pre-EV56 Alpha C11 compiler would need to use LDL_L and
STL_C to carry out 8-bit and 16-bit stores. ;-)
Thanx, Paul
prev parent reply other threads:[~2014-12-04 22:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-04 6:20 [PATCH RFC] locking: Add volatile to arch_spinlock_t structures Paul E. McKenney
[not found] ` <CA+55aFzn-6asfWHB8SAvz4GJWz7uEriujgVLfaqoo_VPtNBLuA@mail.gmail.com>
2014-12-04 6:57 ` Paul E. McKenney
[not found] ` <CA+55aFxGCxQNE4HzRP_Uk2FmFDn_+Hfm6GBz75S+5+SDeODVJQ@mail.gmail.com>
2014-12-04 7:02 ` Paul E. McKenney
2014-12-04 18:02 ` Linus Torvalds
2014-12-04 18:02 ` Linus Torvalds
2014-12-04 18:36 ` Paul E. McKenney
2014-12-04 19:18 ` Linus Torvalds
2014-12-04 20:00 ` Paul E. McKenney
2014-12-04 20:12 ` Paul E. McKenney
2014-12-04 21:45 ` One Thousand Gnomes
2014-12-04 22:06 ` Paul E. McKenney [this message]
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