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* [Bug c++/103878] New: ThreadSanitizer: false report about data race
@ 2021-12-31 15:28 fchelnokov at gmail dot com
2021-12-31 18:53 ` [Bug c++/103878] " redi at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: fchelnokov at gmail dot com @ 2021-12-31 15:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103878
Bug ID: 103878
Summary: ThreadSanitizer: false report about data race
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fchelnokov at gmail dot com
Target Milestone: ---
The program as follows is valid:
```
#include <atomic>
#include <iostream>
#include <future>
int state = 0;
std::atomic_int a = 0;
void foo(int from, int to)
{
for (int i = 0; i < 10; i++)
{
while (a.load(std::memory_order_relaxed) != from) {}
std::atomic_thread_fence(std::memory_order_acquire);
state++;
a.store(to, std::memory_order_release);
}
}
int main()
{
auto x = std::async(std::launch::async, foo, 0, 1);
auto y = std::async(std::launch::async, foo, 1, 0);
}
```
The access to `state` variable is not a data race, because each thread before
the modification executes `atomic_thread_fence` to see the results of the other
thread, and after the modification executes atomic store with
`memory_order_release`. But the sanitizer erroneously reports data race. Demo:
https://gcc.godbolt.org/z/9cY3aM3cz
Related discussion: https://stackoverflow.com/q/70542993/7325599
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/103878] ThreadSanitizer: false report about data race
2021-12-31 15:28 [Bug c++/103878] New: ThreadSanitizer: false report about data race fchelnokov at gmail dot com
@ 2021-12-31 18:53 ` redi at gcc dot gnu.org
2022-01-01 6:24 ` [Bug sanitizer/103878] " pinskia at gcc dot gnu.org
2022-01-01 6:48 ` fchelnokov at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: redi at gcc dot gnu.org @ 2021-12-31 18:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103878
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Isn't this simply the documented limitation of tsan?
https://gcc.gnu.org/onlinedocs/libstdc++/manual/debug.html#debug.races
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug sanitizer/103878] ThreadSanitizer: false report about data race
2021-12-31 15:28 [Bug c++/103878] New: ThreadSanitizer: false report about data race fchelnokov at gmail dot com
2021-12-31 18:53 ` [Bug c++/103878] " redi at gcc dot gnu.org
@ 2022-01-01 6:24 ` pinskia at gcc dot gnu.org
2022-01-01 6:48 ` fchelnokov at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-01-01 6:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103878
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Since it was reported that clang/LLVM have the same issue, is there a bug
report about that?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug sanitizer/103878] ThreadSanitizer: false report about data race
2021-12-31 15:28 [Bug c++/103878] New: ThreadSanitizer: false report about data race fchelnokov at gmail dot com
2021-12-31 18:53 ` [Bug c++/103878] " redi at gcc dot gnu.org
2022-01-01 6:24 ` [Bug sanitizer/103878] " pinskia at gcc dot gnu.org
@ 2022-01-01 6:48 ` fchelnokov at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: fchelnokov at gmail dot com @ 2022-01-01 6:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103878
--- Comment #3 from Fedor Chelnokov <fchelnokov at gmail dot com> ---
Bugreport for Clang/LLVM: https://github.com/llvm/llvm-project/issues/52942
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-01-01 6:48 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-12-31 15:28 [Bug c++/103878] New: ThreadSanitizer: false report about data race fchelnokov at gmail dot com
2021-12-31 18:53 ` [Bug c++/103878] " redi at gcc dot gnu.org
2022-01-01 6:24 ` [Bug sanitizer/103878] " pinskia at gcc dot gnu.org
2022-01-01 6:48 ` fchelnokov at gmail dot com
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