tsan blows up on lazy-static #83
Description
evidence:
- exhibit 1
Lines 20 to 27 in 86d96a4
- exhibit 2 https://github.com/rust-lang/rust/blob/5caca6fa0213cadca1584db43dd71fb5f82b41b9/src/libstd/sync/once.rs#L220
- exhibit 3 https://github.com/rust-lang/rust/blob/5caca6fa0213cadca1584db43dd71fb5f82b41b9/src/libstd/sync/once.rs#L317
story:
basically, tsan doesn't see any relationship between the memory barriers in exhibits 2 & 3 and the dereferenced variable in lazy_static's get() in exhibit 1.
WARNING: ThreadSanitizer: data race (pid=30975)
Read of size 8 at 0x55ddb40e5418 by thread T2:
#0 _$LT$lazy_static..lazy..Lazy$LT$T$GT$$GT$::get::hb947a249eaade5b0 /home/t/.cargo/registry/src/github.com-1ecc6299db9ec823/lazy_static-0.2.8/src/lazy.rs:26 (stress+0x279323)
#1 rayon_core::log::{{impl}}::deref::__stability /home/t/src/rsdb/<__lazy_static_internal macros>:20 (stress+0x2a8520)
#2 _$LT$rayon_core..log..LOG_ENV$u20$as$u20$core..ops..deref..Deref$GT$::deref::h995f5b423216fc8c /home/t/src/rsdb/<__lazy_static_internal macros>:21 (stress+0x2a8520)
#3 rayon_core::registry::WorkerThread::wait_until::h14e38df285736ca7 /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:434 (stress+0x2a0ac1)
#4 rayon_core::registry::WorkerThread::wait_until::h14e38df285736ca7 /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:434 (stress+0x2a0ac1)
#5 rayon_core::registry::main_loop::h120d26ee2b06f3e1 /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:559 (stress+0x2a2ba3)
#6 rayon_core::registry::Registry::new::_$u7b$$u7b$closure$u7d$$u7d$::h73e776a16b1aafcd /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:145 (stress+0x2a87fa)
#7 std::sys_common::backtrace::__rust_begin_short_backtrace::h70e0fa277eccaded /checkout/src/libstd/sys_common/backtrace.rs:136 (stress+0x274b63)
#8 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h73f1afe39e3f5d92 /checkout/src/libstd/thread/mod.rs:364 (stress+0x2772e9)
#9 _$LT$std..panic..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::h0fef211ea8e53025 /checkout/src/libstd/panic.rs:296 (stress+0x269582)
#10 std::panicking::try::do_call::h0164d0443475d14d /checkout/src/libstd/panicking.rs:479 (stress+0x277ab3)
#11 __rust_maybe_catch_panic /checkout/src/libpanic_unwind/lib.rs:98 (stress+0x30999c)
#12 std::panic::catch_unwind::h0f7a13324f48e132 /checkout/src/libstd/panic.rs:361 (stress+0x2761bb)
#13 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::h8fabb47bf4134341 /checkout/src/libstd/thread/mod.rs:363 (stress+0x277091)
#14 _$LT$F$u20$as$u20$alloc..boxed..FnBox$LT$A$GT$$GT$::call_box::h34535139aa115aa0 /checkout/src/liballoc/boxed.rs:652 (stress+0x29081f)
#15 alloc::boxed::{{impl}}::call_once<(),()> /checkout/src/liballoc/boxed.rs:662 (stress+0x30169b)
#16 std::sys_common::thread::start_thread /checkout/src/libstd/sys_common/thread.rs:21 (stress+0x30169b)
#17 std::sys::imp::thread::Thread::new::thread_start::h3eac17b79d7b9487 /checkout/src/libstd/sys/unix/thread.rs:84 (stress+0x30169b)
Previous write of size 8 at 0x55ddb40e5418 by thread T1:
#0 _$LT$lazy_static..lazy..Lazy$LT$T$GT$$GT$::get::_$u7b$$u7b$closure$u7d$$u7d$::he4e15a492cb08e5f /home/t/.cargo/registry/src/github.com-1ecc6299db9ec823/lazy_static-0.2.8/src/lazy.rs:23 (stress+0x27946f)
#1 std::sync::once::Once::call_once::_$u7b$$u7b$closure$u7d$$u7d$::hecb03b941ecc49ae /checkout/src/libstd/sync/once.rs:227 (stress+0x2755f3)
#2 std::sync::once::Once::call_inner::h7a6867e4a5c8eee6 /checkout/src/libstd/sync/once.rs:307 (stress+0x2fbe2c)
#3 _$LT$lazy_static..lazy..Lazy$LT$T$GT$$GT$::get::hb947a249eaade5b0 /home/t/.cargo/registry/src/github.com-1ecc6299db9ec823/lazy_static-0.2.8/src/lazy.rs:22 (stress+0x27930e)
#4 rayon_core::log::{{impl}}::deref::__stability /home/t/src/rsdb/<__lazy_static_internal macros>:20 (stress+0x2a8520)
#5 _$LT$rayon_core..log..LOG_ENV$u20$as$u20$core..ops..deref..Deref$GT$::deref::h995f5b423216fc8c /home/t/src/rsdb/<__lazy_static_internal macros>:21 (stress+0x2a8520)
#6 rayon_core::registry::WorkerThread::wait_until::h14e38df285736ca7 /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:434 (stress+0x2a0ac1)
#7 rayon_core::registry::WorkerThread::wait_until::h14e38df285736ca7 /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:434 (stress+0x2a0ac1)
#8 rayon_core::registry::main_loop::h120d26ee2b06f3e1 /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:559 (stress+0x2a2ba3)
#9 rayon_core::registry::Registry::new::_$u7b$$u7b$closure$u7d$$u7d$::h73e776a16b1aafcd /home/t/src/rsdb/rayon/rayon-core/src/registry.rs:145 (stress+0x2a87fa)
#10 std::sys_common::backtrace::__rust_begin_short_backtrace::h70e0fa277eccaded /checkout/src/libstd/sys_common/backtrace.rs:136 (stress+0x274b63)
#11 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h73f1afe39e3f5d92 /checkout/src/libstd/thread/mod.rs:364 (stress+0x2772e9)
#12 _$LT$std..panic..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::h0fef211ea8e53025 /checkout/src/libstd/panic.rs:296 (stress+0x269582)
#13 std::panicking::try::do_call::h0164d0443475d14d /checkout/src/libstd/panicking.rs:479 (stress+0x277ab3)
#14 __rust_maybe_catch_panic /checkout/src/libpanic_unwind/lib.rs:98 (stress+0x30999c)
#15 std::panic::catch_unwind::h0f7a13324f48e132 /checkout/src/libstd/panic.rs:361 (stress+0x2761bb)
#16 std::thread::Builder::spawn::_$u7b$$u7b$closure$u7d$$u7d$::h8fabb47bf4134341 /checkout/src/libstd/thread/mod.rs:363 (stress+0x277091)
#17 _$LT$F$u20$as$u20$alloc..boxed..FnBox$LT$A$GT$$GT$::call_box::h34535139aa115aa0 /checkout/src/liballoc/boxed.rs:652 (stress+0x29081f)
#18 alloc::boxed::{{impl}}::call_once<(),()> /checkout/src/liballoc/boxed.rs:662 (stress+0x30169b)
#19 std::sys_common::thread::start_thread /checkout/src/libstd/sys_common/thread.rs:21 (stress+0x30169b)
#20 std::sys::imp::thread::Thread::new::thread_start::h3eac17b79d7b9487 /checkout/src/libstd/sys/unix/thread.rs:84 (stress+0x30169b)
Location is global '_$LT$rayon_core..log..LOG_ENV$u20$as$u20$core..ops..deref..Deref$GT$::deref::__stability::LAZY::h79a6f8f41963a1dd' of size 16 at 0x55ddb40e5418 (stress+0x0000013d5418)
Making sure that get uses proper memory barriers on the specific addresses calms its nerves.
// Copyright 2016 lazy-static.rs Developers
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.
extern crate std;
use self::std::prelude::v1::*;
use self::std::sync::atomic::{AtomicPtr, Ordering};
pub struct Lazy<T: Sync>(pub AtomicPtr<T>);
impl<T: Sync> Lazy<T> {
#[inline(always)]
pub fn get<F>(&'static mut self, f: F) -> &T
where F: FnOnce() -> T
{
let initial = 0 as *mut T;
let running = std::usize::MAX as *mut T;
let mut f = Some(f);
loop {
match self.0.load(Ordering::Acquire) {
p if p == initial => {
let res = self.0.compare_and_swap(initial, running, Ordering::Relaxed);
if res == initial {
let res = f.take().unwrap()();
let ptr = Box::into_raw(Box::new(res));
self.0.store(ptr, Ordering::Release);
}
}
p if p == running => {}
initialized => return unsafe { &*initialized },
}
}
}
}
unsafe impl<T: Sync> Sync for Lazy<T> {}
#[macro_export]
#[doc(hidden)]
macro_rules! __lazy_static_create {
($NAME:ident, $T:ty) => {
use std::sync::atomic::AtomicPtr;
static mut $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy(AtomicPtr::new(0 as *mut $T));
}
}It would be nice if I could use lazy_static in multithreaded systems that I'm working on, and require passing tsan!