arm64: rqspinlock: Remove private copy of smp_cond_load_acquire_timewait()

In preparation for defining smp_cond_load_acquire_timeout(), remove
the private copy. Lacking this, the rqspinlock code falls back to using
smp_cond_load_acquire().

Cc: Kumar Kartikeya Dwivedi <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Reviewed-by: Haris Okanovic <[email protected]>
Signed-off-by: Ankur Arora <[email protected]>

Author: terminus

arch/arm64/include/asm/rqspinlock.h

@@ -3,91 +3,6 @@
 #define _ASM_RQSPINLOCK_H
 
 #include <asm/barrier.h>
-
-/*
- * Hardcode res_smp_cond_load_acquire implementations for arm64 to a custom
- * version based on [0]. In rqspinlock code, our conditional expression involves
- * checking the value _and_ additionally a timeout. However, on arm64, the
- * WFE-based implementation may never spin again if no stores occur to the
- * locked byte in the lock word. As such, we may be stuck forever if
- * event-stream based unblocking is not available on the platform for WFE spin
- * loops (arch_timer_evtstrm_available).
- *
- * Once support for smp_cond_load_acquire_timewait [0] lands, we can drop this
- * copy-paste.
- *
- * While we rely on the implementation to amortize the cost of sampling
- * cond_expr for us, it will not happen when event stream support is
- * unavailable, time_expr check is amortized. This is not the common case, and
- * it would be difficult to fit our logic in the time_expr_ns >= time_limit_ns
- * comparison, hence just let it be. In case of event-stream, the loop is woken
- * up at microsecond granularity.
- *
- * [0]: https://lore.kernel.org/lkml/[email protected]
- */
-
-#ifndef smp_cond_load_acquire_timewait
-
-#define smp_cond_time_check_count	200
-
-#define __smp_cond_load_relaxed_spinwait(ptr, cond_expr, time_expr_ns,	\
-					 time_limit_ns) ({		\
-	typeof(ptr) __PTR = (ptr);					\
-	__unqual_scalar_typeof(*ptr) VAL;				\
-	unsigned int __count = 0;					\
-	for (;;) {							\
-		VAL = READ_ONCE(*__PTR);				\
-		if (cond_expr)						\
-			break;						\
-		cpu_relax();						\
-		if (__count++ < smp_cond_time_check_count)		\
-			continue;					\
-		if ((time_expr_ns) >= (time_limit_ns))			\
-			break;						\
-		__count = 0;						\
-	}								\
-	(typeof(*ptr))VAL;						\
-})
-
-#define __smp_cond_load_acquire_timewait(ptr, cond_expr,		\
-					 time_expr_ns, time_limit_ns)	\
-({									\
-	typeof(ptr) __PTR = (ptr);					\
-	__unqual_scalar_typeof(*ptr) VAL;				\
-	for (;;) {							\
-		VAL = smp_load_acquire(__PTR);				\
-		if (cond_expr)						\
-			break;						\
-		__cmpwait_relaxed(__PTR, VAL);				\
-		if ((time_expr_ns) >= (time_limit_ns))			\
-			break;						\
-	}								\
-	(typeof(*ptr))VAL;						\
-})
-
-#define smp_cond_load_acquire_timewait(ptr, cond_expr,			\
-				      time_expr_ns, time_limit_ns)	\
-({									\
-	__unqual_scalar_typeof(*ptr) _val;				\
-	int __wfe = arch_timer_evtstrm_available();			\
-									\
-	if (likely(__wfe)) {						\
-		_val = __smp_cond_load_acquire_timewait(ptr, cond_expr,	\
-							time_expr_ns,	\
-							time_limit_ns);	\
-	} else {							\
-		_val = __smp_cond_load_relaxed_spinwait(ptr, cond_expr,	\
-							time_expr_ns,	\
-							time_limit_ns);	\
-		smp_acquire__after_ctrl_dep();				\
-	}								\
-	(typeof(*ptr))_val;						\
-})
-
-#endif
-
-#define res_smp_cond_load_acquire(v, c) smp_cond_load_acquire_timewait(v, c, 0, 1)
-
 #include <asm-generic/rqspinlock.h>
 
 #endif /* _ASM_RQSPINLOCK_H */