linux-kernel - Re: [PATCH RFC cmpxchg 2/8] sparc: Emulate one-byte and two-byte cmpxchg

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Date: Tue, 2 Apr 2024 05:11:38 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com,
	"David S. Miller" <davem@...emloft.net>,
	Andreas Larsson <andreas@...sler.com>,
	Palmer Dabbelt <palmer@...osinc.com>, Arnd Bergmann <arnd@...db.de>,
	Marco Elver <elver@...gle.com>
Subject: Re: [PATCH RFC cmpxchg 2/8] sparc: Emulate one-byte and two-byte
 cmpxchg

On Tue, Apr 02, 2024 at 04:37:53AM +0100, Al Viro wrote:
> On Tue, Apr 02, 2024 at 01:07:58AM +0100, Al Viro wrote:
> 
> > It does, IIRC.
> > 
> > > Would you like to do that patch?  If so, I would be happy to drop mine
> > > in favor of yours.  If not, could I please have your Signed-off-by so
> > > I can do the Co-developed-by dance?
> > 
> > Will do once I dig my way from under the pile of mail (sick for a week
> > and subscribed to l-k, among other lists)...
> 
> FWIW, parisc is in the same situation - atomics-by-cached-spinlocks.
> 've a candidate branch, will post if it survives build...

Seems to survive.  See
git://git.kernel.org:/pub/scm/linux/kernel/git/viro/vfs.git misc.cmpxchg

Completely untested; builds on several configs, but that's it.
Al Viro (8):
      sparc32: make __cmpxchg_u32() return u32
      sparc32: make the first argument of __cmpxchg_u64() volatile u64 *
      sparc32: unify __cmpxchg_u{32,64}
      sparc32: add __cmpxchg_u{8,16}() and teach __cmpxchg() to handle those sizes
      parisc: __cmpxchg_u32(): lift conversion into the callers
      parisc: unify implementations of __cmpxchg_u{8,32,64}
      parisc: add missing export of __cmpxchg_u8()
      parisc: add u16 support to cmpxchg()

 arch/parisc/include/asm/cmpxchg.h   | 16 ++++++------
 arch/parisc/kernel/parisc_ksyms.c   |  2 ++
 arch/parisc/lib/bitops.c            | 52 ++++++++++++-------------------------
 arch/sparc/include/asm/cmpxchg_32.h | 11 +++++---
 arch/sparc/lib/atomic32.c           | 45 ++++++++++++++------------------
 5 files changed, 55 insertions(+), 71 deletions(-)

Individual patches in followups.