• Davidlohr Bueso's avatar
    arch, locking: Ciao arch_mutex_cpu_relax() · 3a6bfbc9
    Davidlohr Bueso authored
    The arch_mutex_cpu_relax() function, introduced by 34b133f8, is
    hacky and ugly. It was added a few years ago to address the fact
    that common cpu_relax() calls include yielding on s390, and thus
    impact the optimistic spinning functionality of mutexes. Nowadays
    we use this function well beyond mutexes: rwsem, qrwlock, mcs and
    lockref. Since the macro that defines the call is in the mutex header,
    any users must include mutex.h and the naming is misleading as well.
    This patch (i) renames the call to cpu_relax_lowlatency  ("relax, but
    only if you can do it with very low latency") and (ii) defines it in
    each arch's asm/processor.h local header, just like for regular cpu_relax
    functions. On all archs, except s390, cpu_relax_lowlatency is simply cpu_relax,
    and thus we can take it out of mutex.h. While this can seem redundant,
    I believe it is a good choice as it allows us to move out arch specific
    logic from generic locking primitives and enables future(?) archs to
    transparently define it, similarly to System Z.
    Signed-off-by: default avatarDavidlohr Bueso <davidlohr@hp.com>
    Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Anton Blanchard <anton@samba.org>
    Cc: Aurelien Jacquiot <a-jacquiot@ti.com>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Bharat Bhushan <r65777@freescale.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Chen Liqin <liqin.linux@gmail.com>
    Cc: Chris Metcalf <cmetcalf@tilera.com>
    Cc: Christian Borntraeger <borntraeger@de.ibm.com>
    Cc: Chris Zankel <chris@zankel.net>
    Cc: David Howells <dhowells@redhat.com>
    Cc: David S. Miller <davem@davemloft.net>
    Cc: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
    Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
    Cc: Fenghua Yu <fenghua.yu@intel.com>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
    Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
    Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Helge Deller <deller@gmx.de>
    Cc: Hirokazu Takata <takata@linux-m32r.org>
    Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    Cc: James E.J. Bottomley <jejb@parisc-linux.org>
    Cc: James Hogan <james.hogan@imgtec.com>
    Cc: Jason Wang <jasowang@redhat.com>
    Cc: Jesper Nilsson <jesper.nilsson@axis.com>
    Cc: Joe Perches <joe@perches.com>
    Cc: Jonas Bonn <jonas@southpole.se>
    Cc: Joseph Myers <joseph@codesourcery.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
    Cc: Lennox Wu <lennox.wu@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mark Salter <msalter@redhat.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Matt Turner <mattst88@gmail.com>
    Cc: Max Filippov <jcmvbkbc@gmail.com>
    Cc: Michael Neuling <mikey@neuling.org>
    Cc: Michal Simek <monstr@monstr.eu>
    Cc: Mikael Starvik <starvik@axis.com>
    Cc: Nicolas Pitre <nico@linaro.org>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Paul Burton <paul.burton@imgtec.com>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Qais Yousef <qais.yousef@imgtec.com>
    Cc: Qiaowei Ren <qiaowei.ren@intel.com>
    Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Richard Henderson <rth@twiddle.net>
    Cc: Richard Kuo <rkuo@codeaurora.org>
    Cc: Russell King <linux@arm.linux.org.uk>
    Cc: Steven Miao <realmz6@gmail.com>
    Cc: Steven Rostedt <srostedt@redhat.com>
    Cc: Stratos Karafotis <stratosk@semaphore.gr>
    Cc: Tim Chen <tim.c.chen@linux.intel.com>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Vasily Kulikov <segoon@openwall.com>
    Cc: Vineet Gupta <vgupta@synopsys.com>
    Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com>
    Cc: Waiman Long <Waiman.Long@hp.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: Wolfram Sang <wsa@the-dreams.de>
    Cc: adi-buildroot-devel@lists.sourceforge.net
    Cc: linux390@de.ibm.com
    Cc: linux-alpha@vger.kernel.org
    Cc: linux-am33-list@redhat.com
    Cc: linux-arm-kernel@lists.infradead.org
    Cc: linux-c6x-dev@linux-c6x.org
    Cc: linux-cris-kernel@axis.com
    Cc: linux-hexagon@vger.kernel.org
    Cc: linux-ia64@vger.kernel.org
    Cc: linux@lists.openrisc.net
    Cc: linux-m32r-ja@ml.linux-m32r.org
    Cc: linux-m32r@ml.linux-m32r.org
    Cc: linux-m68k@lists.linux-m68k.org
    Cc: linux-metag@vger.kernel.org
    Cc: linux-mips@linux-mips.org
    Cc: linux-parisc@vger.kernel.org
    Cc: linuxppc-dev@lists.ozlabs.org
    Cc: linux-s390@vger.kernel.org
    Cc: linux-sh@vger.kernel.org
    Cc: linux-xtensa@linux-xtensa.org
    Cc: sparclinux@vger.kernel.org
    Link: http://lkml.kernel.org/r/1404079773.2619.4.camel@buesod1.americas.hpqcorp.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
lockref.c 3.63 KB