Commit 3a6bfbc91df04b081a44d419e0260bad54abddf7
Committed by
Ingo Molnar
1 parent
acf5937726
Exists in
ti-lsk-linux-4.1.y
and in
10 other branches
arch, locking: Ciao arch_mutex_cpu_relax()
The arch_mutex_cpu_relax() function, introduced by 34b133f, 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: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Peter 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.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Showing 36 changed files with 51 additions and 25 deletions Side-by-side Diff
- arch/alpha/include/asm/processor.h
- arch/arc/include/asm/processor.h
- arch/arm/include/asm/processor.h
- arch/arm64/include/asm/processor.h
- arch/avr32/include/asm/processor.h
- arch/blackfin/include/asm/processor.h
- arch/c6x/include/asm/processor.h
- arch/cris/include/asm/processor.h
- arch/hexagon/include/asm/processor.h
- arch/ia64/include/asm/processor.h
- arch/m32r/include/asm/processor.h
- arch/m68k/include/asm/processor.h
- arch/metag/include/asm/processor.h
- arch/microblaze/include/asm/processor.h
- arch/mips/include/asm/processor.h
- arch/mn10300/include/asm/processor.h
- arch/openrisc/include/asm/processor.h
- arch/parisc/include/asm/processor.h
- arch/powerpc/include/asm/processor.h
- arch/s390/include/asm/processor.h
- arch/score/include/asm/processor.h
- arch/sh/include/asm/processor.h
- arch/sparc/include/asm/processor_32.h
- arch/sparc/include/asm/processor_64.h
- arch/tile/include/asm/processor.h
- arch/unicore32/include/asm/processor.h
- arch/x86/include/asm/processor.h
- arch/x86/um/asm/processor.h
- arch/xtensa/include/asm/processor.h
- include/linux/mutex.h
- kernel/locking/mcs_spinlock.c
- kernel/locking/mcs_spinlock.h
- kernel/locking/mutex.c
- kernel/locking/qrwlock.c
- kernel/locking/rwsem-xadd.c
- lib/lockref.c
arch/alpha/include/asm/processor.h
arch/arc/include/asm/processor.h
arch/arm/include/asm/processor.h
arch/arm64/include/asm/processor.h
arch/avr32/include/asm/processor.h
arch/blackfin/include/asm/processor.h
... | ... | @@ -99,7 +99,7 @@ |
99 | 99 | #define KSTK_ESP(tsk) ((tsk) == current ? rdusp() : (tsk)->thread.usp) |
100 | 100 | |
101 | 101 | #define cpu_relax() smp_mb() |
102 | - | |
102 | +#define cpu_relax_lowlatency() cpu_relax() | |
103 | 103 | |
104 | 104 | /* Get the Silicon Revision of the chip */ |
105 | 105 | static inline uint32_t __pure bfin_revid(void) |
arch/c6x/include/asm/processor.h
arch/cris/include/asm/processor.h
arch/hexagon/include/asm/processor.h
arch/ia64/include/asm/processor.h
arch/m32r/include/asm/processor.h
arch/m68k/include/asm/processor.h
arch/metag/include/asm/processor.h
arch/microblaze/include/asm/processor.h
arch/mips/include/asm/processor.h
arch/mn10300/include/asm/processor.h
... | ... | @@ -68,7 +68,9 @@ |
68 | 68 | extern void identify_cpu(struct mn10300_cpuinfo *); |
69 | 69 | extern void print_cpu_info(struct mn10300_cpuinfo *); |
70 | 70 | extern void dodgy_tsc(void); |
71 | + | |
71 | 72 | #define cpu_relax() barrier() |
73 | +#define cpu_relax_lowlatency() cpu_relax() | |
72 | 74 | |
73 | 75 | /* |
74 | 76 | * User space process size: 1.75GB (default). |
arch/openrisc/include/asm/processor.h
arch/parisc/include/asm/processor.h
... | ... | @@ -338,6 +338,7 @@ |
338 | 338 | #define KSTK_ESP(tsk) ((tsk)->thread.regs.gr[30]) |
339 | 339 | |
340 | 340 | #define cpu_relax() barrier() |
341 | +#define cpu_relax_lowlatency() cpu_relax() | |
341 | 342 | |
342 | 343 | /* Used as a macro to identify the combined VIPT/PIPT cached |
343 | 344 | * CPUs which require a guarantee of coherency (no inequivalent |
arch/powerpc/include/asm/processor.h
... | ... | @@ -400,6 +400,8 @@ |
400 | 400 | #define cpu_relax() barrier() |
401 | 401 | #endif |
402 | 402 | |
403 | +#define cpu_relax_lowlatency() cpu_relax() | |
404 | + | |
403 | 405 | /* Check that a certain kernel stack pointer is valid in task_struct p */ |
404 | 406 | int validate_sp(unsigned long sp, struct task_struct *p, |
405 | 407 | unsigned long nbytes); |
arch/s390/include/asm/processor.h
arch/score/include/asm/processor.h
arch/sh/include/asm/processor.h
arch/sparc/include/asm/processor_32.h
arch/sparc/include/asm/processor_64.h
arch/tile/include/asm/processor.h
arch/unicore32/include/asm/processor.h
arch/x86/include/asm/processor.h
arch/x86/um/asm/processor.h
arch/xtensa/include/asm/processor.h
include/linux/mutex.h
kernel/locking/mcs_spinlock.c
1 | - | |
2 | 1 | #include <linux/percpu.h> |
3 | -#include <linux/mutex.h> | |
4 | 2 | #include <linux/sched.h> |
5 | 3 | #include "mcs_spinlock.h" |
6 | 4 | |
... | ... | @@ -79,7 +77,7 @@ |
79 | 77 | break; |
80 | 78 | } |
81 | 79 | |
82 | - arch_mutex_cpu_relax(); | |
80 | + cpu_relax_lowlatency(); | |
83 | 81 | } |
84 | 82 | |
85 | 83 | return next; |
... | ... | @@ -120,7 +118,7 @@ |
120 | 118 | if (need_resched()) |
121 | 119 | goto unqueue; |
122 | 120 | |
123 | - arch_mutex_cpu_relax(); | |
121 | + cpu_relax_lowlatency(); | |
124 | 122 | } |
125 | 123 | return true; |
126 | 124 | |
... | ... | @@ -146,7 +144,7 @@ |
146 | 144 | if (smp_load_acquire(&node->locked)) |
147 | 145 | return true; |
148 | 146 | |
149 | - arch_mutex_cpu_relax(); | |
147 | + cpu_relax_lowlatency(); | |
150 | 148 | |
151 | 149 | /* |
152 | 150 | * Or we race against a concurrent unqueue()'s step-B, in which |
kernel/locking/mcs_spinlock.h
... | ... | @@ -27,7 +27,7 @@ |
27 | 27 | #define arch_mcs_spin_lock_contended(l) \ |
28 | 28 | do { \ |
29 | 29 | while (!(smp_load_acquire(l))) \ |
30 | - arch_mutex_cpu_relax(); \ | |
30 | + cpu_relax_lowlatency(); \ | |
31 | 31 | } while (0) |
32 | 32 | #endif |
33 | 33 | |
... | ... | @@ -104,7 +104,7 @@ |
104 | 104 | return; |
105 | 105 | /* Wait until the next pointer is set */ |
106 | 106 | while (!(next = ACCESS_ONCE(node->next))) |
107 | - arch_mutex_cpu_relax(); | |
107 | + cpu_relax_lowlatency(); | |
108 | 108 | } |
109 | 109 | |
110 | 110 | /* Pass lock to next waiter. */ |
kernel/locking/mutex.c
... | ... | @@ -146,7 +146,7 @@ |
146 | 146 | if (need_resched()) |
147 | 147 | break; |
148 | 148 | |
149 | - arch_mutex_cpu_relax(); | |
149 | + cpu_relax_lowlatency(); | |
150 | 150 | } |
151 | 151 | rcu_read_unlock(); |
152 | 152 | |
... | ... | @@ -464,7 +464,7 @@ |
464 | 464 | * memory barriers as we'll eventually observe the right |
465 | 465 | * values at the cost of a few extra spins. |
466 | 466 | */ |
467 | - arch_mutex_cpu_relax(); | |
467 | + cpu_relax_lowlatency(); | |
468 | 468 | } |
469 | 469 | osq_unlock(&lock->osq); |
470 | 470 | slowpath: |
kernel/locking/qrwlock.c
... | ... | @@ -20,7 +20,6 @@ |
20 | 20 | #include <linux/cpumask.h> |
21 | 21 | #include <linux/percpu.h> |
22 | 22 | #include <linux/hardirq.h> |
23 | -#include <linux/mutex.h> | |
24 | 23 | #include <asm/qrwlock.h> |
25 | 24 | |
26 | 25 | /** |
... | ... | @@ -35,7 +34,7 @@ |
35 | 34 | rspin_until_writer_unlock(struct qrwlock *lock, u32 cnts) |
36 | 35 | { |
37 | 36 | while ((cnts & _QW_WMASK) == _QW_LOCKED) { |
38 | - arch_mutex_cpu_relax(); | |
37 | + cpu_relax_lowlatency(); | |
39 | 38 | cnts = smp_load_acquire((u32 *)&lock->cnts); |
40 | 39 | } |
41 | 40 | } |
... | ... | @@ -75,7 +74,7 @@ |
75 | 74 | * to make sure that the write lock isn't taken. |
76 | 75 | */ |
77 | 76 | while (atomic_read(&lock->cnts) & _QW_WMASK) |
78 | - arch_mutex_cpu_relax(); | |
77 | + cpu_relax_lowlatency(); | |
79 | 78 | |
80 | 79 | cnts = atomic_add_return(_QR_BIAS, &lock->cnts) - _QR_BIAS; |
81 | 80 | rspin_until_writer_unlock(lock, cnts); |
... | ... | @@ -114,7 +113,7 @@ |
114 | 113 | cnts | _QW_WAITING) == cnts)) |
115 | 114 | break; |
116 | 115 | |
117 | - arch_mutex_cpu_relax(); | |
116 | + cpu_relax_lowlatency(); | |
118 | 117 | } |
119 | 118 | |
120 | 119 | /* When no more readers, set the locked flag */ |
... | ... | @@ -125,7 +124,7 @@ |
125 | 124 | _QW_LOCKED) == _QW_WAITING)) |
126 | 125 | break; |
127 | 126 | |
128 | - arch_mutex_cpu_relax(); | |
127 | + cpu_relax_lowlatency(); | |
129 | 128 | } |
130 | 129 | unlock: |
131 | 130 | arch_spin_unlock(&lock->lock); |
kernel/locking/rwsem-xadd.c
... | ... | @@ -329,7 +329,7 @@ |
329 | 329 | if (need_resched()) |
330 | 330 | break; |
331 | 331 | |
332 | - arch_mutex_cpu_relax(); | |
332 | + cpu_relax_lowlatency(); | |
333 | 333 | } |
334 | 334 | rcu_read_unlock(); |
335 | 335 | |
... | ... | @@ -381,7 +381,7 @@ |
381 | 381 | * memory barriers as we'll eventually observe the right |
382 | 382 | * values at the cost of a few extra spins. |
383 | 383 | */ |
384 | - arch_mutex_cpu_relax(); | |
384 | + cpu_relax_lowlatency(); | |
385 | 385 | } |
386 | 386 | osq_unlock(&sem->osq); |
387 | 387 | done: |
lib/lockref.c
1 | 1 | #include <linux/export.h> |
2 | 2 | #include <linux/lockref.h> |
3 | -#include <linux/mutex.h> | |
4 | 3 | |
5 | 4 | #if USE_CMPXCHG_LOCKREF |
6 | 5 | |
... | ... | @@ -29,7 +28,7 @@ |
29 | 28 | if (likely(old.lock_count == prev.lock_count)) { \ |
30 | 29 | SUCCESS; \ |
31 | 30 | } \ |
32 | - arch_mutex_cpu_relax(); \ | |
31 | + cpu_relax_lowlatency(); \ | |
33 | 32 | } \ |
34 | 33 | } while (0) |
35 | 34 |
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