From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout02.posteo.de (mout02.posteo.de [185.67.36.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 748B4433E61 for ; Thu, 3 Sep 2026 22:03:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.67.36.66 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788473025; cv=none; b=RiwbWNeojEdOQYgVAC5VR4ZTTUQEz6SqiFJgUnEzmeTCxf2s8u8UBH/yiAJhqdNRAU0B1iE1doSf2kgWtgWs9oUJUPcFdWEaEVNlzmJW0qwVZY+FqbOXtHMEouN8w7+Iq0tB+vcl4TrHnRyPZI8OEn1qjWUkrSrHkI3XUzGIOQ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788473025; c=relaxed/simple; bh=GBcmJnaMQpbIfjUTpYg/eaQYX68BPiVFso1vleOF5JQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=aQwnj6bxnz3Edujt80Xyd/JBICWUyTIUtooUUT+q3xyUmbS8BMaI+ox2LS96abAkAE4Naoit7ccaQ0MlNo3AMRTJUoq3+1cBxbJ/TL5+zwVCVlaZeDN2JpHxP6jOa+GrvKvOHpyQWhw36Z2yr2iGeL4Uu4/yI+pgwZ3wj126adc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de; spf=pass smtp.mailfrom=posteo.de; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b=mtvrc02C; arc=none smtp.client-ip=185.67.36.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=posteo.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b="mtvrc02C" Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 5DA8D240106 for ; Fri, 4 Sep 2026 00:03:40 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=1984.8680eb; t=1788473020; bh=t950fm6K9o0wlrR7qcQVGGcoXGuaXBIxlX9nhhQ5wF4=; h=From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:To:Cc:Autocrypt:OpenPGP:From; b=mtvrc02C85jC4poA5pa8BYa+3yGc6lVN3Qiv1YxYCf4fyHgm1aSW7rtqFozp3a+to /C/E10apcOmVApzF/8gjnudexctFIKZMQX7WNa710utup6XMx0mfOys4OqfFYAaaIA BxDBcuEM/1keUsORnTKAzYMo4fv1Swbmd9NFDp5KLOquqCft+WjdAZidbi4XpjyTvc WnAmlau4oLQHWy3XLJfH2unuQSPjDqhT0ZF5BTVfmhpBrjdKGblzzFQFDFBiV9JnnY KfJC0K0veh7jfZpy+suwqjNMK5WSNGJLBDjhV9wijL2UjY9kdDnABx8DN8uMkNqEqN HX2/67jYbPLyQ== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4hbYWq6p5Tz9rxB; Fri, 4 Sep 2026 00:03:35 +0200 (CEST) From: Markus Probst Date: Thu, 03 Sep 2026 22:03:39 +0000 Subject: [PATCH] rust: serdev: Synchronize receive callback before calling unbind Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260904-rust_serdev_ref_mut-v1-1-245db7eb09af@posteo.de> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/y2N2wrCMBBEfyXss5E0aqP9FSkhTVaNkLbmhlD67 67Wx8PMmVkgYfSYoGMLRKw++WkkaHYM7MOMd+TeEYMUshUXceCxpKxJclh1xJsOJfOjk/J8Uqo 12ACZMwX+/Vu99hunMjzR5u/UvxHxVegubzUYTEJupxB87lhVe3qyDfTr+gGS3FeTowAAAA== X-Change-ID: 20260903-rust_serdev_ref_mut-4d2285776ae1 To: Ayush Singh , Johan Hovold , Alex Elder , Greg Kroah-Hartman , Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?utf-8?q?Onur_=C3=96zkan?= , Eric Biggers , Ard Biesheuvel , Lorenzo Stoakes , Vlastimil Babka , "Liam R. 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Provide mutable references in callbacks to avoid the need for locks in the private data. Remove the Sync requirement. Signed-off-by: Markus Probst --- This patch avoids the need for a SpinLock in the patch series https://lore.kernel.org/rust-for-linux/20260827-gb-uart-transport-v2-7-a03bb1f5fbd1@beagleboard.org/ . --- rust/kernel/serdev.rs | 51 ++++++++++++++++++++++---------------- samples/rust/rust_driver_serdev.rs | 2 +- 2 files changed, 31 insertions(+), 22 deletions(-) diff --git a/rust/kernel/serdev.rs b/rust/kernel/serdev.rs index 17ca504b7f8d..44f029ed93fd 100644 --- a/rust/kernel/serdev.rs +++ b/rust/kernel/serdev.rs @@ -106,7 +106,7 @@ pub struct PrivateData<'bound, T: Driver> { /// Whether `receive_buf_callback` is allowed to call `Driver::receive`. /// /// If locked, the receive_buf_callback will be blocked on data reception. - /// This is the case while the driver is being probed or while [`PrivateData`] is being dropped. + /// This is the case while the driver is being probed or removed. /// This is necessary, because we need to open the serdev device before the driver has been /// probed in order to allow it to be configured, which allows `receive_buf_callback` to be /// called. Thus we need to block data until probe completes and the driver data becomes @@ -127,16 +127,6 @@ pub struct PrivateData<'bound, T: Driver> { #[pinned_drop] impl PinnedDrop for PrivateData<'_, T> { fn drop(self: Pin<&mut Self>) { - let mut active = self.active.lock(); - if *active { - // SAFETY: - // - We have exclusive access to `self.driver`. - // - `self.driver` is guaranteed to be initialized. - unsafe { (*self.driver.get()).assume_init_drop() }; - *active = false; - } - drop(active); - // SAFETY: We have exclusive access to `self.open`. if unsafe { *self.open.get() } { // SAFETY: `self.sdev.as_raw()` is guaranteed to be a pointer to a valid @@ -176,7 +166,20 @@ extern "C" fn probe_callback(sdev: *mut bindings::serdev_device) -> kernel::ffi: let private_data = unsafe { sdev.as_ref().drvdata_borrow::>() }; let private_data = ScopeGuard::new_with_data(private_data, |_| { // SAFETY: We just set drvdata to `PrivateData<'_, T>`. - drop(unsafe { sdev.as_ref().drvdata_obtain::>() }); + let private_data = unsafe { + sdev.as_ref() + .drvdata_obtain::>() + .unwrap_unchecked() + }; + + let mut active = private_data.active.lock(); + if *active { + // SAFETY: + // - We have exclusive access to `private_data.driver`. + // - `private_data.driver` is guaranteed to be initialized. + unsafe { (*private_data.driver.get()).assume_init_drop() }; + *active = false; + } }); let mut active = private_data.active.lock(); @@ -222,15 +225,21 @@ extern "C" fn remove_callback(sdev: *mut bindings::serdev_device) { // and stored a `Pin>>`. let private_data = unsafe { sdev.as_ref().drvdata_borrow::>() }; - // SAFETY: No one has exclusive access to `private_data.driver`. - let data = unsafe { &*private_data.driver.get() }; + let mut active = private_data.active.lock(); + + // SAFETY: We have exclusive access to `private_data.driver`. + let data = unsafe { &mut *private_data.driver.get() }; // SAFETY: // - `private_data.driver` is pinned. // - `remove_callback` is only ever called after a successful call to `probe_callback`, // hence it's guaranteed that `private_data.driver` was initialized. - let data_pinned = unsafe { Pin::new_unchecked(data.assume_init_ref()) }; + let data_pinned = unsafe { Pin::new_unchecked(data.assume_init_mut()) }; T::unbind(sdev, data_pinned); + + // SAFETY: We already established that `data` is guaranteed to be initialized. + unsafe { data.assume_init_drop() }; + *active = false; } extern "C" fn receive_buf_callback( @@ -254,13 +263,13 @@ extern "C" fn receive_buf_callback( return length; } - // SAFETY: No one has exclusive access to `private_data.driver`. - let data = unsafe { &*private_data.driver.get() }; + // SAFETY: We have exclusive access to `private_data.driver`. + let data = unsafe { &mut *private_data.driver.get() }; // SAFETY: // - `private_data.driver` is pinned. // - `receive_buf_callback` is only ever called after a successful call to `probe_callback`, // hence it's guaranteed that `private_data.driver` was initialized. - let data_pinned = unsafe { Pin::new_unchecked(data.assume_init_ref()) }; + let data_pinned = unsafe { Pin::new_unchecked(data.assume_init_mut()) }; // SAFETY: `buf` is guaranteed to be non-null and has the size of `length`. let buf = unsafe { core::slice::from_raw_parts(buf, length) }; @@ -365,7 +374,7 @@ pub trait Driver { type IdInfo: 'static; /// The type of the driver's bus device private data. - type Data<'bound>: Send + Sync + 'bound; + type Data<'bound>: Send + 'bound; /// The table of OF device ids supported by the driver. const OF_ID_TABLE: Option> = None; @@ -391,7 +400,7 @@ fn probe<'bound>( /// `&Device` or `&Device` reference. For instance. /// /// Otherwise, release operations for driver resources should be performed in `Drop`. - fn unbind<'bound>(sdev: &'bound Device>, this: Pin<&Self::Data<'bound>>) { + fn unbind<'bound>(sdev: &'bound Device>, this: Pin<&mut Self::Data<'bound>>) { let _ = (sdev, this); } @@ -402,7 +411,7 @@ fn unbind<'bound>(sdev: &'bound Device>, this: Pin<&Self::Data< /// Returns the number of bytes accepted. fn receive<'bound>( sdev: &'bound Device, - this: Pin<&Self::Data<'bound>>, + this: Pin<&mut Self::Data<'bound>>, data: &[u8], ) -> usize { let _ = (sdev, this, data); diff --git a/samples/rust/rust_driver_serdev.rs b/samples/rust/rust_driver_serdev.rs index 51b4898cd855..d00d547234c8 100644 --- a/samples/rust/rust_driver_serdev.rs +++ b/samples/rust/rust_driver_serdev.rs @@ -63,7 +63,7 @@ fn probe<'bound>( fn receive<'bound>( sdev: &'bound serdev::Device, - _this: Pin<&Self>, + _this: Pin<&mut Self>, data: &[u8], ) -> usize { sdev.write(data).unwrap_or_default() as usize --- base-commit: e5e04726cdd043e309677071ab1b65a4b18f422b change-id: 20260903-rust_serdev_ref_mut-4d2285776ae1