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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
cc: Alexander Lakhin <exclusion@gmail.com>,
 Andres Freund <andres@anarazel.de>,
        pgsql-hackers <pgsql-hackers@postgresql.org>, greg@burd.me
Subject: Re: IO in wrong state on riscv64
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
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Date: Sat, 08 Nov 2025 14:26:14 -0500
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... BTW, I wonder why you did not add pg_compiler_barrier_impl()
to our other use of __atomic_thread_fence:

#if !defined(pg_memory_barrier_impl)
#    if defined(HAVE_GCC__ATOMIC_INT32_CAS)
#        define pg_memory_barrier_impl()        __atomic_thread_fence(__AT=
OMIC_SEQ_CST)
#    elif defined(__GNUC__)
#        define pg_memory_barrier_impl()        __sync_synchronize()
#    endif
#endif /* !defined(pg_memory_barrier_impl) */

If the problem is that Clang doesn't treat __atomic_thread_fence
as a compiler barrier, why is this usage safer than the other two?

			regards, tom lane