+ arm64-rqspinlock-remove-private-copy-of-smp_cond_load_acquire_timewait.patch added to mm-new branch

+ arm64-rqspinlock-remove-private-copy-of-smp_cond_load_acquire_timewait.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: arm64: rqspinlock: remove private copy of smp_cond_load_acquire_timewait()
has been added to the -mm mm-new branch.  Its filename is
     arm64-rqspinlock-remove-private-copy-of-smp_cond_load_acquire_timewait.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-rqspinlock-remove-private-copy-of-smp_cond_load_acquire_timewait.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Ankur Arora <ankur.a.arora@oracle.com>
Subject: arm64: rqspinlock: remove private copy of smp_cond_load_acquire_timewait()
Date: Wed, 8 Apr 2026 17:55:29 +0530

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().

Link: https://lore.kernel.org/20260408122538.3610871-6-ankur.a.arora@oracle.com
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Haris Okanovic <harisokn@amazon.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: David Gow <davidgow@google.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Konrad Dybcio <konradybcio@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm64/include/asm/rqspinlock.h |   85 --------------------------
 1 file changed, 85 deletions(-)

--- a/arch/arm64/include/asm/rqspinlock.h~arm64-rqspinlock-remove-private-copy-of-smp_cond_load_acquire_timewait
+++ a/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/20250203214911.898276-1-ankur.a.arora@oracle.com
- */
-
-#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 */
_

Patches currently in -mm which might be from ankur.a.arora@oracle.com are

asm-generic-barrier-add-smp_cond_load_relaxed_timeout.patch
arm64-barrier-support-smp_cond_load_relaxed_timeout.patch
arm64-delay-move-some-constants-out-to-a-separate-header.patch
arm64-support-wfet-in-smp_cond_load_relaxed_timeout.patch
arm64-rqspinlock-remove-private-copy-of-smp_cond_load_acquire_timewait.patch
asm-generic-barrier-add-smp_cond_load_acquire_timeout.patch
atomic-add-atomic_cond_read__timeout.patch
locking-atomic-scripts-build-atomic_long_cond_read__timeout.patch
bpf-rqspinlock-switch-check_timeout-to-a-clock-interface.patch
bpf-rqspinlock-use-smp_cond_load_acquire_timeout.patch
sched-add-need-resched-timed-wait-interface.patch
cpuidle-poll_state-wait-for-need-resched-via-tif_need_resched_relaxed_wait.patch
kunit-enable-testing-smp_cond_load_relaxed_timeout.patch
kunit-add-tests-for-smp_cond_load_relaxed_timeout.patch