linux-kernel - [PATCH v8 2/6] ww_mutex: add `ww

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Message-ID: <20251201102855.4413-3-work@onurozkan.dev>
Date: Mon,  1 Dec 2025 13:28:51 +0300
From: Onur Özkan <work@...rozkan.dev>
To: rust-for-linux@...r.kernel.org
Cc: lossin@...nel.org,
	lyude@...hat.com,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	dakr@...nel.org,
	peterz@...radead.org,
	mingo@...hat.com,
	will@...nel.org,
	longman@...hat.com,
	felipe_life@...e.com,
	daniel@...lak.dev,
	daniel.almeida@...labora.com,
	thomas.hellstrom@...ux.intel.com,
	linux-kernel@...r.kernel.org,
	Onur Özkan <work@...rozkan.dev>
Subject: [PATCH v8 2/6] ww_mutex: add `ww_class` field unconditionally

Removes `DEBUG_WW_MUTEXES` guard on ww_class field
from ww_acquire_ctx and ww_mutex.

This helps us to write much safer Rust abstraction
in very simple way.

Link: https://lore.kernel.org/all/ECC0425A-8B18-4626-8EA8-2F843C45E0A1@collabora.com/
Signed-off-by: Onur Özkan <work@...rozkan.dev>
---
 include/linux/ww_mutex.h | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index 45ff6f7a872b..c9835035b6d6 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -47,9 +47,7 @@ struct ww_class {
 struct ww_mutex {
 	struct WW_MUTEX_BASE base;
 	struct ww_acquire_ctx *ctx;
-#ifdef DEBUG_WW_MUTEXES
 	struct ww_class *ww_class;
-#endif
 };
 
 struct ww_acquire_ctx {
@@ -58,9 +56,9 @@ struct ww_acquire_ctx {
 	unsigned int acquired;
 	unsigned short wounded;
 	unsigned short is_wait_die;
+	struct ww_class *ww_class;
 #ifdef DEBUG_WW_MUTEXES
 	unsigned int done_acquire;
-	struct ww_class *ww_class;
 	void *contending_lock;
 #endif
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -110,9 +108,7 @@ static inline void ww_mutex_init(struct ww_mutex *lock,
 {
 	ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key);
 	lock->ctx = NULL;
-#ifdef DEBUG_WW_MUTEXES
 	lock->ww_class = ww_class;
-#endif
 }
 
 /**
@@ -147,8 +143,8 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
 	ctx->acquired = 0;
 	ctx->wounded = false;
 	ctx->is_wait_die = ww_class->is_wait_die;
-#ifdef DEBUG_WW_MUTEXES
 	ctx->ww_class = ww_class;
+#ifdef DEBUG_WW_MUTEXES
 	ctx->done_acquire = 0;
 	ctx->contending_lock = NULL;
 #endif
-- 
2.51.2