From nobody Sat Feb 7 21:20:36 2026 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CD75E1AD9D4 for ; Tue, 13 Aug 2024 23:57:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723593470; cv=none; b=iW+db4HKPJod7MVktTmQRqM3QKc0ey3+3THhdvadP7oE74IE0K01EwC55hMWXsXrZNqzGvNbkcPQVkEkAhp8S1OtYmErlFYjc0KfkR+JFUPHmaQg17NqnWx3Qp/G6lhbyD++gNd0Bjf31HeIQZ9EsUwu0OHQem/gcQnE2NVMMKA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723593470; c=relaxed/simple; bh=Hx7qT79zV3diP9nx80oNpiGlO7TpIuO5gTbeRUzmgV4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=V9uPKbGcKd6MTH1fGpRC6DCw1+tpb1N/crVLhn/sdQ77KAz8y9c6bbWmtafMJUatAbjx6LFJUFCxqzMSzxd8GQL6Ld9NuYjgxj/uovmuxzzUNBb3Y1o4L4IMk7hX+yErvmm7LsNpRRVSjSDmEkeSYgGMR4cQxzkDRfZpJChvygU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=sW/Rt03q; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jstultz.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="sW/Rt03q" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-70d14709555so5161783b3a.2 for ; Tue, 13 Aug 2024 16:57:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1723593468; x=1724198268; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=R/92V8zxLqTBZSee0wU+b7QjFoMd91sCzJfYaFAS4N4=; b=sW/Rt03qxjjfCD88v/6n/FX7nmyeIDuS1sp9GLQaKzMsy/xKJpgMmaZoHe/u1b2x+e 0kKgn0mFbC6iYrxhWmj9dCfFq6kppuP/l8z7kIj387eXRx+ZpwCR7rkMnebz1GAh0AWc B9Nk7rn2B1Lp3Vw827R+9AnJ23TFqW0TasFivonpiR4mwTW0sdfHErfpQH8Ct5mQVmZi SLsKNthZt04BkHvE7+QWoa5jFReU7K8I+SkGx0ewoA6Bc61KBNUsfReFdyO9zIklNV2f T5N/KeCEK8pTgPm2VHaj+JyQI+6a+VQJmpjEHF9pATkYPFN1k4+OgWxPq/Drvxvib87O PuJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723593468; x=1724198268; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=R/92V8zxLqTBZSee0wU+b7QjFoMd91sCzJfYaFAS4N4=; b=jNsl7ftH17UMX92wXfJLmiImGKL+WO03S//bfQp6lJ6FSnaTxVXfVkdmUm782VQsWj EMLM8J/TWn+rOsoKj8acIj7fVI5ErbM8LrA8EVjVyEhKF4TAiSY4d0fFslCO8Y1EcihU dw4ynCLMXojjmYVtbLPKhSoT2C+2ktkXlef8OSi45eM1hmM8ShP8wONNBWcS5CiOHzZ1 Pzw9+o9Q50J22LkfLVKNjI9QPT7GCS05t3uMLibIrRTLGbVelkjEWGbcHJzkndHrMMEP r8tfxu38Yb10oljdRKuueVVDijLmDZhWxhKJliFbKH463hZ1hIlvi3zucWTR0eNk8Ufy ohDA== X-Gm-Message-State: AOJu0YxnzKz1L0xFaRO7W1AAw6RXONerOtOy1S0q0VFRTNxyzDJ33+nR K1ZMUZswIA7lCCjhCbqasGiZ7jFqC5SdW4ZPsmOUNdIE0SYqksSoHUSuzmhehAlyP1iFv+3sDdp XAvyPRNFuCLomYeCUwD3emdq4TNdVmR3vRZvLRvnZRS9PjVINslWb0B44ZpTH95BGTOY7qzB9aQ TvDYhRXxCROXQQz2Ke78lVC6ZSo56GFEPQTkk3iLk+nOhk X-Google-Smtp-Source: AGHT+IHlhSZeCl5hPJDIJzN1hSPE1054K78MmKqSDqxGvVBQMouJu0iQa9f9cFXg2YZbDYK2mIo903pbxU/s X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a05:6a00:3e29:b0:710:5798:44de with SMTP id d2e1a72fcca58-712671036abmr14557b3a.2.1723593466656; Tue, 13 Aug 2024 16:57:46 -0700 (PDT) Date: Tue, 13 Aug 2024 16:57:23 -0700 In-Reply-To: <20240813235736.1744280-1-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240813235736.1744280-1-jstultz@google.com> X-Mailer: git-send-email 2.46.0.76.ge559c4bf1a-goog Message-ID: <20240813235736.1744280-4-jstultz@google.com> Subject: [PATCH v12 3/7] locking/mutex: Expose __mutex_owner() From: John Stultz To: LKML Cc: Juri Lelli , Joel Fernandes , Qais Yousef , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Mel Gorman , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , Daniel Lezcano , kernel-team@android.com, Metin Kaya , Valentin Schneider , "Connor O'Brien" , John Stultz Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Juri Lelli Implementing proxy execution requires that scheduler code be able to identify the current owner of a mutex. Expose __mutex_owner() for this purpose (alone!). Includes a null mutex check, so that users of the function can be simplified. Cc: Joel Fernandes Cc: Qais Yousef Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Valentin Schneider Cc: Steven Rostedt Cc: Ben Segall Cc: Zimuzo Ezeozue Cc: Mel Gorman Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Cc: Metin Kaya Cc: Xuewen Yan Cc: K Prateek Nayak Cc: Thomas Gleixner Cc: Daniel Lezcano Cc: kernel-team@android.com Tested-by: K Prateek Nayak Tested-by: Metin Kaya Reviewed-by: Metin Kaya Reviewed-by: Valentin Schneider Signed-off-by: Juri Lelli [Removed the EXPORT_SYMBOL] Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien [jstultz: Reworked per Peter's suggestions] Signed-off-by: John Stultz --- v4: * Move __mutex_owner() to kernel/locking/mutex.h instead of adding a new globally available accessor function to keep the exposure of this low, along with keeping it an inline function, as suggested by PeterZ v10: * Handle null lock ptr, to simplify later code, as suggested by Metin Kaya v11: * Tweak commit message suggested by Metin Kaya --- kernel/locking/mutex.c | 25 ------------------------- kernel/locking/mutex.h | 27 +++++++++++++++++++++++++++ 2 files changed, 27 insertions(+), 25 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index cd248d1767eb3..3302e52f0c967 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -56,31 +56,6 @@ __mutex_init(struct mutex *lock, const char *name, struc= t lock_class_key *key) } EXPORT_SYMBOL(__mutex_init); =20 -/* - * @owner: contains: 'struct task_struct *' to the current lock owner, - * NULL means not owned. Since task_struct pointers are aligned at - * at least L1_CACHE_BYTES, we have low bits to store extra state. - * - * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. - * Bit1 indicates unlock needs to hand the lock to the top-waiter - * Bit2 indicates handoff has been done and we're waiting for pickup. - */ -#define MUTEX_FLAG_WAITERS 0x01 -#define MUTEX_FLAG_HANDOFF 0x02 -#define MUTEX_FLAG_PICKUP 0x04 - -#define MUTEX_FLAGS 0x07 - -/* - * Internal helper function; C doesn't allow us to hide it :/ - * - * DO NOT USE (outside of mutex code). - */ -static inline struct task_struct *__mutex_owner(struct mutex *lock) -{ - return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLA= GS); -} - static inline struct task_struct *__owner_task(unsigned long owner) { return (struct task_struct *)(owner & ~MUTEX_FLAGS); diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h index 0b2a79c4013bd..cbff35b9b7ae3 100644 --- a/kernel/locking/mutex.h +++ b/kernel/locking/mutex.h @@ -20,6 +20,33 @@ struct mutex_waiter { #endif }; =20 +/* + * @owner: contains: 'struct task_struct *' to the current lock owner, + * NULL means not owned. Since task_struct pointers are aligned at + * at least L1_CACHE_BYTES, we have low bits to store extra state. + * + * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. + * Bit1 indicates unlock needs to hand the lock to the top-waiter + * Bit2 indicates handoff has been done and we're waiting for pickup. + */ +#define MUTEX_FLAG_WAITERS 0x01 +#define MUTEX_FLAG_HANDOFF 0x02 +#define MUTEX_FLAG_PICKUP 0x04 + +#define MUTEX_FLAGS 0x07 + +/* + * Internal helper function; C doesn't allow us to hide it :/ + * + * DO NOT USE (outside of mutex & scheduler code). + */ +static inline struct task_struct *__mutex_owner(struct mutex *lock) +{ + if (!lock) + return NULL; + return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLA= GS); +} + #ifdef CONFIG_DEBUG_MUTEXES extern void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter); --=20 2.46.0.76.ge559c4bf1a-goog