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* [musl] Mutexes are not unlocking
@ 2020-11-20  5:25 a
  2020-11-20  5:58 ` Rich Felker
  0 siblings, 1 reply; 20+ messages in thread
From: a @ 2020-11-20  5:25 UTC (permalink / raw)
  To: musl

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Hello, all,
I am experiencing a problem with mutexes in musl-libc. The mutex is not unlocked after calling unlock(), this causes getting stuck on attempt to lock it next time. Example code (C++):

void testMutex(std::mutex &mtx, const char * name) {
fprintf(stderr, "-- testing %s --\n", name);
fprintf(stderr, "lock\n");
mtx.lock();
fprintf(stderr, "unlock\n");
mtx.unlock();
fprintf(stderr, "lock2\n");
mtx.lock();
fprintf(stderr, "unlock2\n");
mtx.unlock();
fprintf(stderr, "done\n");
} The problem can be reproduced only on musl-libc, the same binary works well on the system with glibc.
The problem does not reproduce each time, its reproducibility depends on the phase of moon.
The problem can be reproduced more often it the code calling mutex functions is located in the shared library.

Strace (when the problem is reproduced):
[pid   709] writev(2, [{iov_base="-- testing gsMutex --\n", iov_len=22}, {iov_base=NULL, iov_len=0}], 2-- testing gsMutex -- 
) = 22 
[pid   709] writev(2, [{iov_base="", iov_len=0}, {iov_base="lock\n", iov_len=5}], 2lock 
) = 5 
[pid   709] writev(2, [{iov_base="", iov_len=0}, {iov_base="unlock\n", iov_len=7}], 2unlock 
) = 7 
[pid   709] writev(2, [{iov_base="", iov_len=0}, {iov_base="lock2\n", iov_len=6}], 2lock2 
) = 6 
[pid   709] futex(0x7f3a9733e4a4, FUTEX_WAIT_PRIVATE, 2147483664, NULL

Strace (when the problem is not reproduced):
writev(2, [{iov_base="-- testing hhMutex --\n", iov_len=22}, {iov_base=NULL, iov_len=0}], 2-- testing hhMutex -- 
) = 22 
writev(2, [{iov_base="", iov_len=0}, {iov_base="lock\n", iov_len=5}], 2lock 
) = 5 
writev(2, [{iov_base="", iov_len=0}, {iov_base="unlock\n", iov_len=7}], 2unlock 
) = 7 
writev(2, [{iov_base="", iov_len=0}, {iov_base="lock2\n", iov_len=6}], 2lock2 
) = 6 
writev(2, [{iov_base="", iov_len=0}, {iov_base="unlock2\n", iov_len=8}], 2unlock2 
) = 8 
writev(2, [{iov_base="", iov_len=0}, {iov_base="done\n", iov_len=5}], 2done 
) = 5

Thanks in advance for solving the problem.

—— 
Arseniy

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^ permalink raw reply	[flat|nested] 20+ messages in thread

end of thread, other threads:[~2020-11-23 17:19 UTC | newest]

Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-20  5:25 [musl] Mutexes are not unlocking a
2020-11-20  5:58 ` Rich Felker
2020-11-21  6:46   ` Re[2]: " a
2020-11-21 15:51     ` Rich Felker
2020-11-22 18:43       ` Re[2]: " Арсений
2020-11-22 19:11         ` Rich Felker
2020-11-22 19:23           ` Florian Weimer
2020-11-22 19:28             ` Rich Felker
2020-11-22 19:45               ` Re[2]: " Арсений
2020-11-22 20:05               ` Арсений
2020-11-23 12:24                 ` Jonathan Wakely
2020-11-23 14:56                   ` Rich Felker
2020-11-23 16:58                     ` Jonathan Wakely
2020-11-23 11:41               ` Jonathan Wakely
2020-11-23 14:53                 ` Rich Felker
2020-11-23 16:19                   ` Jonathan Wakely
2020-11-23 16:51                     ` Rich Felker
2020-11-23 17:10                       ` Jonathan Wakely
2020-11-23 17:18                         ` Florian Weimer
2020-11-23 16:59                     ` Florian Weimer

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