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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nptl/24774] pthread_rwlock_timedwrlock stalls on ARM
Date: Wed, 08 Sep 2021 06:19:54 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D24774

--- Comment #4 from Florian Weimer <fweimer at redhat dot com> ---
This looks like a bug in our atomics, as reported here:

Glibc pthread_rwlock_timed*() Optimization Bug
https://sourceware.org/pipermail/libc-help/2021-September/006004.html

include/atomic.h has:

# ifndef atomic_load_relaxed
#  define atomic_load_relaxed(mem) \
   ({ __typeof ((__typeof (*(mem))) *(mem)) __atg100_val;                  =
   \
   __asm ("" : "=3Dr" (__atg100_val) : "0" (*(mem)));                      =
     \
   __atg100_val; })
# endif

The expression *(mem) does not necessary read from the memory location.

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