From patchwork Thu Apr 6 21:56:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Almeida X-Patchwork-Id: 13204270 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50CAAC77B71 for ; Thu, 6 Apr 2023 21:58:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235839AbjDFV5i (ORCPT ); Thu, 6 Apr 2023 17:57:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238783AbjDFV5N (ORCPT ); Thu, 6 Apr 2023 17:57:13 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62F12B453; Thu, 6 Apr 2023 14:56:37 -0700 (PDT) Received: from localhost.localdomain (unknown [IPv6:2804:14d:72b4:8284:32a8:8167:f815:2895]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dwlsalmeida) by madras.collabora.co.uk (Postfix) with ESMTPSA id B759766031D9; Thu, 6 Apr 2023 22:56:33 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1680818196; bh=Z1mWh6lO7+hdoozjzHbSbRzBrAE3llpM//4UJUMybns=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QAQepvs3Zbpe0+7Y9i4iiyVuHrSwrwPxURN0SnPqlGdXKKV2xwAcxDJo/g7rthf6F tKTIaCLdCWpceHIn/aD/e2JtpmxEJNGtLOdAsZiA7JxNK0cBxGsFj5+LVQq6+t7cLP cO2vM1NDzL5Cf93rZ/tHahn8YVzTJgGYBf1QcjiaqVgFi+5lqYNu7VHmeLfEZIZ5UD OJEvHEtuYBWTyx/nslLupNS5l+EEkWXRvBy/id14oXNfTExAsgV2Fqf+KFxzPD+1Ow wpTVW+O5X4Kzaykh/HAxMQt+Cp8AlxWHTJb8b0KY3Qzc3RB1D+2aCHESAzurWihORA Olef4SVXq8PYQ== From: Daniel Almeida To: wedsonaf@gmail.com, ojeda@kernel.org, mchehab@kernel.org, hverkuil@xs4all.nl Cc: Daniel Almeida , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, kernel@collabora.com Subject: [PATCH 3/6] rust: sync: introduce FfiMutex Date: Thu, 6 Apr 2023 18:56:12 -0300 Message-Id: <20230406215615.122099-4-daniel.almeida@collabora.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230406215615.122099-1-daniel.almeida@collabora.com> References: <20230406215615.122099-1-daniel.almeida@collabora.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Introduce an owned mutex that can be passed as bindings::mutex when initializing C data structures. The kernel will be locking it without user intervention so there is no data to protect and no guard type. Signed-off-by: Daniel Almeida --- rust/kernel/sync.rs | 1 + rust/kernel/sync/ffi_mutex.rs | 70 +++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+) create mode 100644 rust/kernel/sync/ffi_mutex.rs diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index b07db83972ac..1415062be34d 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -26,6 +26,7 @@ use core::{cell::UnsafeCell, mem::MaybeUninit, pin::Pin}; mod arc; mod condvar; +pub mod ffi_mutex; mod guard; mod locked_by; mod mutex; diff --git a/rust/kernel/sync/ffi_mutex.rs b/rust/kernel/sync/ffi_mutex.rs new file mode 100644 index 000000000000..e615ec4059f6 --- /dev/null +++ b/rust/kernel/sync/ffi_mutex.rs @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! An owned mutex that can be passed as bindings::mutex when initializing C +//! data structures. The kernel will be locking it without user intervention so +//! there is no data to protect and no guard type. + +#![allow(dead_code)] + +use crate::prelude::*; +use crate::sync::{LockClassKey, LockIniter}; +use core::marker::PhantomPinned; +use core::pin::Pin; + +use crate::Opaque; + +/// An owned mutex that can be passed as bindings::mutex when initializing C +/// data structures. The kernel will be locking it without user intervention so +/// there is no data to protect and no guard type. +pub struct FfiMutex { + mutex: Opaque, + _pin: PhantomPinned, +} + +impl FfiMutex { + /// Constructs a new Mutex for FFI purposes. + /// + /// # Safety + /// + /// The caller must call [`FfiMutex::init_lock`] before using the raw Mutex. + pub const unsafe fn new() -> Self { + Self { + mutex: Opaque::uninit(), + _pin: PhantomPinned, + } + } + + /// Returns the inner bindings::mutex + /// + /// # Safety + /// + /// The caller must call [`FfiMutex::init_lock`] before using the raw Mutex. + pub(crate) unsafe fn raw(self: &mut Pin<&mut Self>) -> *mut bindings::mutex { + let this = self.as_mut(); + // SAFETY: mutex is pinned when Lock is. The argument to the function is not moved. + let this = unsafe { this.map_unchecked_mut(|x| &mut x.mutex) }; + // This does not move from the field. + this.get() + } +} + +impl LockIniter for FfiMutex { + fn init_lock(self: Pin<&mut Self>, name: &'static CStr, key: &'static LockClassKey) { + unsafe { bindings::__mutex_init(self.mutex.get(), name.as_char_ptr(), key.get()) }; + } +} + +// SAFETY: the underlying bindings::mutex can be used from any thread. +unsafe impl Send for FfiMutex {} +// SAFETY: two threads can try locking the underlying bindings::mutex at the +// same thread without issues. +unsafe impl Sync for FfiMutex {} + +/// Safely initialises a [`FfiMutex`] with the given name, generating a new lock +/// class. +#[macro_export] +macro_rules! ffi_mutex_init { + ($mutex:expr, $name:literal) => { + $crate::init_with_lockdep!($mutex, $name); + }; +}