From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f202.google.com (mail-dy1-f202.google.com [74.125.82.202]) (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 69650472784 for ; Mon, 11 May 2026 17:50:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778521812; cv=none; b=qAV5h+5kZf3WU29URkzAddUnAxNKBv+Bdbuq0neNPeHdaABwi/68qxbf0P+Mba+fj2SXsbsMTWgtr2s7VbJn5u4hz4OcEnRHOe0WoW6mUyewdihgLA2lNhhRyoGAduw31kCLMkf010sXQYbp0iPpk9PT3BmSSdnCOaUBuJ1P0D0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778521812; c=relaxed/simple; bh=Oq67dXaTV+BHjGRbysYou0ulHtDM/4BziolaYr9VX4g=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=OGOnA2fc3QL67J3b9wrRBhju7+0ZAF6w3Y+czbeWa6vjzDhTr4YjQeOoksfpcM8EPWh979HGroQHqn0hpVhuxfDdz8CzqGjw7AaZ7iXjB7gpuEuZbAT/tu7Ex983TT+8RMW0TXGNIrereiC54+pz1WGDlieD5+QfZHtjPWMmCeA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--wusamuel.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=FgiouSv6; arc=none smtp.client-ip=74.125.82.202 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--wusamuel.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="FgiouSv6" Received: by mail-dy1-f202.google.com with SMTP id 5a478bee46e88-2f5943ca81aso4307995eec.0 for ; Mon, 11 May 2026 10:50:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778521810; x=1779126610; 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=/Hxl2WZ9OZBQQeGr1zOYQYix9RVHeZZ/4ou1EYE8Zvc=; b=FgiouSv6VjkmVA3VSULStTRpIh/teWFFANtwx6w7HQRmL3GX0faS0yimcSvqmKuG9G EmrmPvTADnb1xcfTxXbnzpvFKW/s+WYx5RAQthf2QhZUnug26v3SoiGrIu1f4ef5+6zM FNkkcMzZYxzR09xPgtsIyiNYs07m4zeWxL77Ufy9tos2C3rCpHUkbDYNQSbvZzFcfTYh DyFvPALODrO35FbuleQRsy2GzovV+SjDQQNXRKWyKZv/+K/KaIgvnmHJ2bg0HQFyD9c0 1mXzCWaSwE16WoG3X9IoMxKS3nlyg+G5YNU9I6gF7qOw1Emn/QxK6KOQorOV+sFjrqoX c7AQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778521810; x=1779126610; 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=/Hxl2WZ9OZBQQeGr1zOYQYix9RVHeZZ/4ou1EYE8Zvc=; b=oOD6pl2jx1MhISylUxFfifsnO0SU9oUup+oY+u2153/9cn2Aqv0jrBkhacbtt1LLdB ZA0OgeVRHQP8w+8ZeFpLPcrQXQP7GFjqnbZPtRHDkO/PRf3axPnZpOZxSPotzW3Fxc3A 5ZNjnPFrHqSUpLmMb8rwb/5RpF9HPUe6L0K1Oaqyy5nawqpEYmQYfGIhCY6MafdhTIHT TLRou/2bZPYtbLGT0j9EOo20bfMvXp4bWiQQzXIbUPO+EPHOQY7fcIy0cpJCJRFfPc6K 029Tss7e/G83Fgta7tTG5IOMI7gGujQe1ElaZ1bpMQvBqsDSkL8+opCNfBI6+VPsqj5i gmNg== X-Forwarded-Encrypted: i=1; AFNElJ9W2L4r4d7FGdcP3R9pQmizhcUXz9AJsai5pWNcWuLILITYZA6hSUpbJ9olWjccckljTO+e90QHKqFdNSI=@vger.kernel.org X-Gm-Message-State: AOJu0YzrS82of42S2ry1PRDunVx55+CkXmtIGx/78erES6pgGw96q+hm 7wP0tG4vgEZvTURcle7ZhPMfZ1D2PAbCt8NwhAD9zusCT0o63FXff6joZNb+huMJbtzPgkSiGX3 nnyK+mRY6YVU0jw== X-Received: from dybkf34.prod.google.com ([2002:a05:7301:3aa2:b0:2f7:1410:b095]) (user=wusamuel job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7301:19a5:b0:2dd:6937:79b8 with SMTP id 5a478bee46e88-2fb3dbf98bamr5182384eec.5.1778521810205; Mon, 11 May 2026 10:50:10 -0700 (PDT) Date: Mon, 11 May 2026 10:45:56 -0700 In-Reply-To: <20260511174559.659782-1-wusamuel@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260511174559.659782-1-wusamuel@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260511174559.659782-2-wusamuel@google.com> Subject: [PATCH v4 1/2] PM: wakeup: Add kfuncs to traverse over wakeup_sources From: Samuel Wu To: "Rafael J. Wysocki" , Pavel Machek , Len Brown , Greg Kroah-Hartman , Danilo Krummrich , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , Shuah Khan Cc: Samuel Wu , kernel-team@android.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, driver-core@lists.linux.dev, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Iterating through wakeup sources via sysfs or debugfs can be inefficient or restricted. Introduce BPF kfuncs to allow high-performance and safe in-kernel traversal of the wakeup_sources list. There is at least a 30x speedup for walking 150 wakeup sources and all their attributes. The new kfuncs include: - bpf_wakeup_sources_get_head() to obtain the list head. - bpf_wakeup_sources_read_lock/unlock() to manage the SRCU lock. For verifier safety, the underlying SRCU index is wrapped in an opaque 'struct bpf_ws_lock' pointer. This enables the use of KF_ACQUIRE and KF_RELEASE flags, allowing the BPF verifier to strictly enforce paired lock/unlock cycles and prevent resource leaks. Signed-off-by: Samuel Wu --- drivers/base/power/power.h | 7 ++++ drivers/base/power/wakeup.c | 71 +++++++++++++++++++++++++++++++++++-- 2 files changed, 76 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h index 922ed457db19..8823aceeac8b 100644 --- a/drivers/base/power/power.h +++ b/drivers/base/power/power.h @@ -168,3 +168,10 @@ static inline void device_pm_init(struct device *dev) device_pm_sleep_init(dev); pm_runtime_init(dev); } + +#ifdef CONFIG_BPF_SYSCALL +struct bpf_ws_lock { }; +struct bpf_ws_lock *bpf_wakeup_sources_read_lock(void); +void bpf_wakeup_sources_read_unlock(struct bpf_ws_lock *lock); +void *bpf_wakeup_sources_get_head(void); +#endif diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c index b8e48a023bf0..80b497de2deb 100644 --- a/drivers/base/power/wakeup.c +++ b/drivers/base/power/wakeup.c @@ -1168,11 +1168,78 @@ static const struct file_operations wakeup_sources_stats_fops = { .release = seq_release_private, }; -static int __init wakeup_sources_debugfs_init(void) +#ifdef CONFIG_BPF_SYSCALL +#include + +__bpf_kfunc_start_defs(); + +/** + * bpf_wakeup_sources_read_lock - Acquire the SRCU lock for wakeup sources + * + * The underlying SRCU lock returns an integer index. However, the BPF verifier + * requires a pointer (PTR_TO_BTF_ID) to strictly track the state of acquired + * resources using KF_ACQUIRE and KF_RELEASE semantics. We use an opaque + * structure pointer (struct bpf_ws_lock *) to satisfy the verifier while + * safely encoding the integer index within the pointer address itself. + * + * Return: An opaque pointer encoding the SRCU lock index + 1 (to avoid NULL). + */ +__bpf_kfunc struct bpf_ws_lock *bpf_wakeup_sources_read_lock(void) +{ + return (struct bpf_ws_lock *)(long)(wakeup_sources_read_lock() + 1); +} + +/** + * bpf_wakeup_sources_read_unlock - Release the SRCU lock for wakeup sources + * @lock: The opaque pointer returned by bpf_wakeup_sources_read_lock() + * + * The BPF verifier guarantees that @lock is a valid, unreleased pointer from + * the acquire function. We decode the pointer back into the integer SRCU index + * by subtracting 1 and release the lock. + */ +__bpf_kfunc void bpf_wakeup_sources_read_unlock(struct bpf_ws_lock *lock) +{ + wakeup_sources_read_unlock((int)(long)lock - 1); +} + +/** + * bpf_wakeup_sources_get_head - Get the head of the wakeup sources list + * + * Return: The head of the wakeup sources list. + */ +__bpf_kfunc void *bpf_wakeup_sources_get_head(void) +{ + return &wakeup_sources; +} + +__bpf_kfunc_end_defs(); + +BTF_KFUNCS_START(wakeup_source_kfunc_ids) +BTF_ID_FLAGS(func, bpf_wakeup_sources_read_lock, KF_ACQUIRE) +BTF_ID_FLAGS(func, bpf_wakeup_sources_read_unlock, KF_RELEASE) +BTF_ID_FLAGS(func, bpf_wakeup_sources_get_head) +BTF_KFUNCS_END(wakeup_source_kfunc_ids) + +static const struct btf_kfunc_id_set wakeup_source_kfunc_set = { + .set = &wakeup_source_kfunc_ids, +}; + +static void __init wakeup_sources_bpf_init(void) +{ + if (register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &wakeup_source_kfunc_set)) + pm_pr_dbg("Wakeup: failed to register BTF kfuncs\n"); +} +#else +static inline void wakeup_sources_bpf_init(void) {} +#endif /* CONFIG_BPF_SYSCALL */ + +static int __init wakeup_sources_init(void) { debugfs_create_file("wakeup_sources", 0444, NULL, NULL, &wakeup_sources_stats_fops); + wakeup_sources_bpf_init(); + return 0; } -postcore_initcall(wakeup_sources_debugfs_init); +postcore_initcall(wakeup_sources_init); -- 2.54.0.563.g4f69b47b94-goog