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* [Bug locale/28206] New: Data race in implementation of glibc functions newlocale() and/or freelocale()
@ 2021-08-07 13:48 kristian.spangsege at gmail dot com
2021-08-07 13:52 ` [Bug locale/28206] " kristian.spangsege at gmail dot com
2021-08-07 13:55 ` kristian.spangsege at gmail dot com
0 siblings, 2 replies; 3+ messages in thread
From: kristian.spangsege at gmail dot com @ 2021-08-07 13:48 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28206
Bug ID: 28206
Summary: Data race in implementation of glibc functions
newlocale() and/or freelocale()
Product: glibc
Version: 2.31
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: locale
Assignee: unassigned at sourceware dot org
Reporter: kristian.spangsege at gmail dot com
Target Milestone: ---
Created attachment 13597
--> https://sourceware.org/bugzilla/attachment.cgi?id=13597&action=edit
Demonstrate using C, then C++
According to the thread sanitizer, there is a data race in the implementation
of newlocale() and/or freelocale() in glibc 2.31 (Linux Mint 20).
As demonstrated by the attached C program (locale_1.c), when more than one
thread creates and destroys a locale using locale name `C.UTF-8`, the program
will sometimes crash.
Here is the first part of the output from the thread sanitizer:
==================
WARNING: ThreadSanitizer: data race (pid=165699)
Write of size 8 at 0x7b0400000000 by thread T2:
#0 free ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:711
(libtsan.so.0+0x37ab8)
#1 <null> <null> (libc.so.6+0x34f0c)
#2 thread <null> (a.out+0x12ea)
Previous write of size 8 at 0x7b0400000000 by thread T1:
[failed to restore the stack]
Thread T2 (tid=165702, running) created by main thread at:
#0 pthread_create
../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:969
(libtsan.so.0+0x605f8)
#1 main <null> (a.out+0x1366)
Thread T1 (tid=165701, running) created by main thread at:
#0 pthread_create
../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:969
(libtsan.so.0+0x605f8)
#1 main <null> (a.out+0x1366)
SUMMARY: ThreadSanitizer: data race (/lib/x86_64-linux-gnu/libc.so.6+0x34f0c)
==================
Presumable, the C++ locale system is built on top of newlocale() and
freelocale(), and therefore, as expected, similar reports of data races occur
when using the C++ locale system. This is demonstrated by the attached C++
program (locale_2.cpp).
Compilation:
gcc -pthread -D_XOPEN_SOURCE=700 -fsanitize=thread locale_1.c
g++ -pthread -std=c++17 -fsanitize=thread locale_2.cpp
I also tried with GCC 7 and GCC 11 specifically, but that didn't change
anything.
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* [Bug locale/28206] Data race in implementation of glibc functions newlocale() and/or freelocale()
2021-08-07 13:48 [Bug locale/28206] New: Data race in implementation of glibc functions newlocale() and/or freelocale() kristian.spangsege at gmail dot com
@ 2021-08-07 13:52 ` kristian.spangsege at gmail dot com
2021-08-07 13:55 ` kristian.spangsege at gmail dot com
1 sibling, 0 replies; 3+ messages in thread
From: kristian.spangsege at gmail dot com @ 2021-08-07 13:52 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28206
--- Comment #1 from kristian.spangsege at gmail dot com <kristian.spangsege at gmail dot com> ---
(In reply to kristian.spangsege@gmail.com from comment #0)
>
> As demonstrated by the attached C program (locale_1.c), when more than one
> thread creates and destroys a locale using locale name `C.UTF-8`, the
> program will sometimes crash.
Oops, I mean to say, "data races will be reported" rather than "the program
will sometimes crash". It doesn't seem to ever crash. Sorry about the
confusion.
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* [Bug locale/28206] Data race in implementation of glibc functions newlocale() and/or freelocale()
2021-08-07 13:48 [Bug locale/28206] New: Data race in implementation of glibc functions newlocale() and/or freelocale() kristian.spangsege at gmail dot com
2021-08-07 13:52 ` [Bug locale/28206] " kristian.spangsege at gmail dot com
@ 2021-08-07 13:55 ` kristian.spangsege at gmail dot com
1 sibling, 0 replies; 3+ messages in thread
From: kristian.spangsege at gmail dot com @ 2021-08-07 13:55 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28206
--- Comment #2 from kristian.spangsege at gmail dot com <kristian.spangsege at gmail dot com> ---
By the way, here is a godbolt link that demonstrates the problem:
https://godbolt.org/z/bxW8E7oTx
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2021-08-07 13:48 [Bug locale/28206] New: Data race in implementation of glibc functions newlocale() and/or freelocale() kristian.spangsege at gmail dot com
2021-08-07 13:52 ` [Bug locale/28206] " kristian.spangsege at gmail dot com
2021-08-07 13:55 ` kristian.spangsege at gmail dot com
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