From: comex <comexk@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Kent Overstreet" <kent.overstreet@linux.dev>,
"Boqun Feng" <boqun.feng@gmail.com>,
rust-for-linux <rust-for-linux@vger.kernel.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
llvm@lists.linux.dev, "Miguel Ojeda" <ojeda@kernel.org>,
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"Wedson Almeida Filho" <wedsonaf@gmail.com>,
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"Daniel Lustig" <dlustig@nvidia.com>,
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linux-fsdevel@vger.kernel.org
Subject: Re: [WIP 0/3] Memory model and atomic API in Rust
Date: Sat, 23 Mar 2024 17:40:23 -0400 [thread overview]
Message-ID: <C85BE4F4-5847-45B4-A973-76B184B35EDE@gmail.com> (raw)
In-Reply-To: <CAHk-=whY5A=S=bLwCFL=043DoR0TTgSDUmfPDx2rXhkk3KANPQ@mail.gmail.com>
> On Mar 22, 2024, at 8:12 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> And when the compiler itself is fundamentally buggy, you're kind of
> screwed. When you roll your own, you can work around the bugs in
> compilers.
That may be true, but the LLVM issue you cited isn’t a good example. In that issue, the function being miscompiled doesn’t actually use any barriers or atomics itself; only the scaffolding around it does. The same issue would happen even if the scaffolding used LKMM atomics.
For anyone curious: The problematic optimization involves an allocation (‘p’) that is initially private to the function, but is returned at the end of the function. LLVM moves a non-atomic store to that allocation across an external function call (to ‘foo’). This reordering would be blatantly invalid if any other code could observe the contents of the allocation, but is valid if the allocation is private to the function. LLVM assumes the latter: after all, the pointer to it hasn’t escaped. Yet. Except that in a weak memory model, the escape can ‘time travel’...
next prev parent reply other threads:[~2024-03-23 21:40 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-22 23:38 Boqun Feng
2024-03-22 23:38 ` [WIP 1/3] rust: Introduce atomic module Boqun Feng
2024-03-22 23:52 ` Andrew Lunn
2024-03-23 0:03 ` Boqun Feng
2024-03-23 19:13 ` Miguel Ojeda
2024-03-23 19:30 ` Boqun Feng
2024-03-23 9:58 ` Alice Ryhl
2024-03-23 14:10 ` Andrew Lunn
2024-03-23 19:09 ` Miguel Ojeda
2024-03-26 5:56 ` Trevor Gross
2024-03-22 23:38 ` [WIP 2/3] rust: atomic: Add ARM64 fetch_add_relaxed() Boqun Feng
2024-03-22 23:38 ` [WIP 3/3] rust: atomic: Add fetch_sub_release() Boqun Feng
2024-03-22 23:57 ` [WIP 0/3] Memory model and atomic API in Rust Kent Overstreet
2024-03-23 0:12 ` Linus Torvalds
2024-03-23 0:21 ` Kent Overstreet
2024-03-23 0:36 ` Linus Torvalds
2024-03-23 2:07 ` Kent Overstreet
2024-03-23 2:26 ` Boqun Feng
2024-03-23 2:33 ` Kent Overstreet
2024-03-23 2:57 ` Boqun Feng
2024-03-23 3:10 ` Kent Overstreet
2024-03-23 3:51 ` Boqun Feng
2024-03-23 4:16 ` Kent Overstreet
2024-03-25 13:56 ` Philipp Stanner
2024-03-25 17:44 ` Linus Torvalds
2024-03-25 18:59 ` Kent Overstreet
2024-03-25 19:44 ` Linus Torvalds
2024-03-25 21:14 ` Kent Overstreet
2024-03-25 21:37 ` Boqun Feng
2024-03-25 22:09 ` Kent Overstreet
2024-03-25 22:38 ` Boqun Feng
2024-03-25 23:02 ` Kent Overstreet
2024-03-25 23:41 ` Boqun Feng
2024-03-26 0:05 ` Dr. David Alan Gilbert
2024-03-26 0:36 ` Kent Overstreet
2024-03-26 1:35 ` Dr. David Alan Gilbert
2024-03-26 3:28 ` Kent Overstreet
2024-03-26 2:51 ` Boqun Feng
2024-03-26 3:49 ` Linus Torvalds
2024-03-26 14:35 ` Dr. David Alan Gilbert
2024-03-27 16:16 ` comex
2024-03-27 18:50 ` Kent Overstreet
2024-03-27 19:07 ` Linus Torvalds
2024-03-27 19:41 ` Kent Overstreet
2024-03-27 20:45 ` Linus Torvalds
2024-03-27 21:41 ` Kent Overstreet
2024-03-27 22:57 ` Linus Torvalds
2024-03-27 23:35 ` Kent Overstreet
2024-03-27 21:21 ` Boqun Feng
2024-03-27 21:49 ` Kent Overstreet
2024-03-27 22:26 ` Boqun Feng
2024-03-27 21:56 ` comex
2024-03-27 22:02 ` comex
2024-04-05 17:13 ` Philipp Stanner
2024-04-08 16:02 ` Matthew Wilcox
2024-04-08 16:55 ` Paul E. McKenney
2024-04-08 17:03 ` Matthew Wilcox
2024-04-08 18:47 ` Paul E. McKenney
2024-04-09 0:58 ` Kent Overstreet
2024-04-09 4:47 ` Paul E. McKenney
2024-04-08 17:01 ` Linus Torvalds
2024-04-08 18:14 ` Al Viro
2024-04-08 20:05 ` Linus Torvalds
2024-03-23 21:40 ` comex [this message]
2024-03-24 15:22 ` Alan Stern
2024-03-24 17:37 ` comex
2024-03-23 0:15 ` Boqun Feng
2024-03-23 0:49 ` Boqun Feng
2024-03-23 1:42 ` Kent Overstreet
2024-03-23 14:29 ` Andrew Lunn
2024-03-23 14:41 ` Boqun Feng
2024-03-23 14:55 ` Boqun Feng
2024-03-25 10:44 ` Mark Rutland
2024-03-25 20:59 ` Boqun Feng
2024-04-09 10:50 ` Peter Zijlstra
2024-04-16 18:12 ` Boqun Feng
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