From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 ABAF513DDB8; Thu, 25 Jul 2024 14:37:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721918255; cv=none; b=tE37Oo5cF8mttBCDIjTJgSDzTNiY5U6jDu1/XylqipaCX1JTIaSw1el80ikQ/CkM1PZ440+HIcjZ3bj9jRH81zDBx0F1pupiWvj/npPivoR54CfmIWqptV14nt1iS+oAgv6FjEUmDSJAQK5LPC+h5cxhzuixNikkdC6UGk5259I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721918255; c=relaxed/simple; bh=jsKLe1xfJkO7kNI862YjLgzfKiNT8Bh+4bl/90ow/D0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nn1jZMjGbLqc+dXUZRecRQ0B0P4+HnaPooPc/cejT6oEyS2ZJQ4W5K2lwT5a5BadtRw0rdgrZ5JWA2TBxO/UjG9poHp9Wmj7yLbMCjrptH+w4eIruFLtF+2wE97GZ+9Odt+FWLc0NNPDDifUoqZm5N+PVjVXy/7XoC2AAGuyhgQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Rmmqq1Ci; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Rmmqq1Ci" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=L7B4J3xfdz2Y6tZKoIVkSSXHyah9IYkeN+4fghJY3iE=; b=Rmmqq1CiqxGeNspuQMxERRfFPc OTR5qILQnYfTfksJ6bzZAIR3nKtqysigmp2T/k/YC6vkAaL9+HNhGQTQvCDKTCx9mKJOgN7OfX1ve ebin00wmz2oSg8PLZJJtfeu8xEM6GtEwaPE2y2gk8rcl8970cMd7qTF1riN1uZ4mGPV2fS1Hom9FV 8PrhpUtOZYRHRyt8FqYG21dYJFOQufMAY0T1+Y7qoBBgKEUeW9Sp/qbFZ/QtWMGMMdd6bc0ahYBed gBJOUgLTq3deARf0t4MlOP/HadV00aoqgG43YJakBS4NHTwt3DcoyowogJBPHjwVFs2eb+IOKCUeP wRJjO5sA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sWzam-0000000914G-2mCn; Thu, 25 Jul 2024 14:37:16 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 939F630037B; Thu, 25 Jul 2024 16:37:14 +0200 (CEST) Date: Thu, 25 Jul 2024 16:37:14 +0200 From: Peter Zijlstra To: Alice Ryhl Cc: Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alexander Viro , Christian Brauner , Greg Kroah-Hartman , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Todd Kjos , Martijn Coenen , Joel Fernandes , Carlos Llamas , Suren Baghdasaryan , Dan Williams , Matthew Wilcox , Thomas Gleixner , Daniel Xu , Martin Rodriguez Reboredo , Trevor Gross , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-fsdevel@vger.kernel.org, Kees Cook Subject: Re: [PATCH v8 1/8] rust: types: add `NotThreadSafe` Message-ID: <20240725143714.GI13387@noisy.programming.kicks-ass.net> References: <20240725-alice-file-v8-0-55a2e80deaa8@google.com> <20240725-alice-file-v8-1-55a2e80deaa8@google.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240725-alice-file-v8-1-55a2e80deaa8@google.com> On Thu, Jul 25, 2024 at 02:27:34PM +0000, Alice Ryhl wrote: > This introduces a new marker type for types that shouldn't be thread > safe. By adding a field of this type to a struct, it becomes non-Send > and non-Sync, which means that it cannot be accessed in any way from > threads other than the one it was created on. > > This is useful for APIs that require globals such as `current` to remain > constant while the value exists. > > We update two existing users in the Kernel to use this helper: > > * `Task::current()` - moving the return type of this value to a > different thread would not be safe as you can no longer be guaranteed > that the `current` pointer remains valid. > * Lock guards. Mutexes and spinlocks should be unlocked on the same > thread as where they were locked, so we enforce this using the Send > trait. > > There are also additional users in later patches of this patchset. See > [1] and [2] for the discussion that led to the introduction of this > patch. > > Link: https://lore.kernel.org/all/nFDPJFnzE9Q5cqY7FwSMByRH2OAn_BpI4H53NQfWIlN6I2qfmAqnkp2wRqn0XjMO65OyZY4h6P4K2nAGKJpAOSzksYXaiAK_FoH_8QbgBI4=@proton.me/ [1] > Link: https://lore.kernel.org/all/nFDPJFnzE9Q5cqY7FwSMByRH2OAn_BpI4H53NQfWIlN6I2qfmAqnkp2wRqn0XjMO65OyZY4h6P4K2nAGKJpAOSzksYXaiAK_FoH_8QbgBI4=@proton.me/ [2] > Suggested-by: Benno Lossin > Reviewed-by: Benno Lossin > Reviewed-by: Trevor Gross > Reviewed-by: Martin Rodriguez Reboredo > Reviewed-by: Björn Roy Baron > Signed-off-by: Alice Ryhl > --- > rust/kernel/sync/lock.rs | 13 +++++++++---- > rust/kernel/task.rs | 10 ++++++---- > rust/kernel/types.rs | 21 +++++++++++++++++++++ > 3 files changed, 36 insertions(+), 8 deletions(-) > > diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs > index f6c34ca4d819..d6e9bab114b8 100644 > --- a/rust/kernel/sync/lock.rs > +++ b/rust/kernel/sync/lock.rs > @@ -6,8 +6,13 @@ > //! spinlocks, raw spinlocks) to be provided with minimal effort. > > use super::LockClassKey; > -use crate::{init::PinInit, pin_init, str::CStr, types::Opaque, types::ScopeGuard}; > -use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned}; > +use crate::{ > + init::PinInit, > + pin_init, > + str::CStr, > + types::{NotThreadSafe, Opaque, ScopeGuard}, > +}; > +use core::{cell::UnsafeCell, marker::PhantomPinned}; > use macros::pin_data; > > pub mod mutex; > @@ -139,7 +144,7 @@ pub fn lock(&self) -> Guard<'_, T, B> { > pub struct Guard<'a, T: ?Sized, B: Backend> { > pub(crate) lock: &'a Lock, > pub(crate) state: B::GuardState, > - _not_send: PhantomData<*mut ()>, > + _not_send: NotThreadSafe, > } > > // SAFETY: `Guard` is sync when the data protected by the lock is also sync. > @@ -191,7 +196,7 @@ pub(crate) unsafe fn new(lock: &'a Lock, state: B::GuardState) -> Self { > Self { > lock, > state, > - _not_send: PhantomData, > + _not_send: NotThreadSafe, > } > } > } > diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs > index 55dff7e088bf..278c623de0c6 100644 > --- a/rust/kernel/task.rs > +++ b/rust/kernel/task.rs > @@ -4,10 +4,12 @@ > //! > //! C header: [`include/linux/sched.h`](srctree/include/linux/sched.h). > > -use crate::types::Opaque; > +use crate::{ > + bindings, > + types::{NotThreadSafe, Opaque}, > +}; > use core::{ > ffi::{c_int, c_long, c_uint}, > - marker::PhantomData, > ops::Deref, > ptr, > }; > @@ -106,7 +108,7 @@ impl Task { > pub unsafe fn current() -> impl Deref { > struct TaskRef<'a> { > task: &'a Task, > - _not_send: PhantomData<*mut ()>, > + _not_send: NotThreadSafe, > } > > impl Deref for TaskRef<'_> { > @@ -125,7 +127,7 @@ fn deref(&self) -> &Self::Target { > // that `TaskRef` is not `Send`, we know it cannot be transferred to another thread > // (where it could potentially outlive the caller). > task: unsafe { &*ptr.cast() }, > - _not_send: PhantomData, > + _not_send: NotThreadSafe, > } > } As per always for not being able to read rust; how does this extend to get_task_struct()? Once you've taken a reference on current, you should be free to pass it along to whomever.