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authorPeter Zijlstra <peterz@infradead.org>2016-06-01 13:23:54 -0400
committerIngo Molnar <mingo@kernel.org>2016-06-14 05:55:14 -0400
commit7cb45c0fe9858f92cc264f6bf9d2f6a0e7d3b249 (patch)
treef429581d6b993e303a297a461d06cd0dad58ea68
parent33ac279677dcc2441cb93d8cb9cf7a74df62814d (diff)
locking/barriers: Move smp_cond_load_acquire() to asm-generic/barrier.h
Since all asm/barrier.h should/must include asm-generic/barrier.h the latter is a good place for generic infrastructure like this. This also allows archs to override the new smp_acquire__after_ctrl_dep(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--include/asm-generic/barrier.h39
-rw-r--r--include/linux/compiler.h37
2 files changed, 39 insertions, 37 deletions
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 1cceca146905..ab7b0bd7d4dd 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -207,5 +207,44 @@ do { \
207#define virt_store_release(p, v) __smp_store_release(p, v) 207#define virt_store_release(p, v) __smp_store_release(p, v)
208#define virt_load_acquire(p) __smp_load_acquire(p) 208#define virt_load_acquire(p) __smp_load_acquire(p)
209 209
210/**
211 * smp_acquire__after_ctrl_dep() - Provide ACQUIRE ordering after a control dependency
212 *
213 * A control dependency provides a LOAD->STORE order, the additional RMB
214 * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order,
215 * aka. (load)-ACQUIRE.
216 *
217 * Architectures that do not do load speculation can have this be barrier().
218 */
219#ifndef smp_acquire__after_ctrl_dep
220#define smp_acquire__after_ctrl_dep() smp_rmb()
221#endif
222
223/**
224 * smp_cond_load_acquire() - (Spin) wait for cond with ACQUIRE ordering
225 * @ptr: pointer to the variable to wait on
226 * @cond: boolean expression to wait for
227 *
228 * Equivalent to using smp_load_acquire() on the condition variable but employs
229 * the control dependency of the wait to reduce the barrier on many platforms.
230 *
231 * Due to C lacking lambda expressions we load the value of *ptr into a
232 * pre-named variable @VAL to be used in @cond.
233 */
234#ifndef smp_cond_load_acquire
235#define smp_cond_load_acquire(ptr, cond_expr) ({ \
236 typeof(ptr) __PTR = (ptr); \
237 typeof(*ptr) VAL; \
238 for (;;) { \
239 VAL = READ_ONCE(*__PTR); \
240 if (cond_expr) \
241 break; \
242 cpu_relax(); \
243 } \
244 smp_acquire__after_ctrl_dep(); \
245 VAL; \
246})
247#endif
248
210#endif /* !__ASSEMBLY__ */ 249#endif /* !__ASSEMBLY__ */
211#endif /* __ASM_GENERIC_BARRIER_H */ 250#endif /* __ASM_GENERIC_BARRIER_H */
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 59a7004fc7dd..2e853b679a5d 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -304,43 +304,6 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
304 __u.__val; \ 304 __u.__val; \
305}) 305})
306 306
307/**
308 * smp_acquire__after_ctrl_dep() - Provide ACQUIRE ordering after a control dependency
309 *
310 * A control dependency provides a LOAD->STORE order, the additional RMB
311 * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order,
312 * aka. (load)-ACQUIRE.
313 *
314 * Architectures that do not do load speculation can have this be barrier().
315 */
316#define smp_acquire__after_ctrl_dep() smp_rmb()
317
318/**
319 * smp_cond_load_acquire() - (Spin) wait for cond with ACQUIRE ordering
320 * @ptr: pointer to the variable to wait on
321 * @cond: boolean expression to wait for
322 *
323 * Equivalent to using smp_load_acquire() on the condition variable but employs
324 * the control dependency of the wait to reduce the barrier on many platforms.
325 *
326 * Due to C lacking lambda expressions we load the value of *ptr into a
327 * pre-named variable @VAL to be used in @cond.
328 */
329#ifndef smp_cond_load_acquire
330#define smp_cond_load_acquire(ptr, cond_expr) ({ \
331 typeof(ptr) __PTR = (ptr); \
332 typeof(*ptr) VAL; \
333 for (;;) { \
334 VAL = READ_ONCE(*__PTR); \
335 if (cond_expr) \
336 break; \
337 cpu_relax(); \
338 } \
339 smp_acquire__after_ctrl_dep(); \
340 VAL; \
341})
342#endif
343
344#endif /* __KERNEL__ */ 307#endif /* __KERNEL__ */
345 308
346#endif /* __ASSEMBLY__ */ 309#endif /* __ASSEMBLY__ */