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([2602:ae:1598:4c01:86cc:4482:68db:2c0f]) by smtp.gmail.com with ESMTPSA id n6-20020a170902e54600b001afa7040a70sm3413086plf.276.2023.05.26.08.55.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 May 2023 08:55:33 -0700 (PDT) Message-ID: <3e797413-a8ee-ecd3-8775-b22107cd0418@linaro.org> Date: Fri, 26 May 2023 08:55:31 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH] atomics: eliminate mb_read/mb_set Content-Language: en-US To: Paolo Bonzini , qemu-devel@nongnu.org References: <20230526081810.423315-1-pbonzini@redhat.com> From: Richard Henderson In-Reply-To: <20230526081810.423315-1-pbonzini@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::536; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x536.google.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.092, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 5/26/23 01:18, Paolo Bonzini wrote: > qatomic_mb_read and qatomic_mb_set were the very first atomic primitives > introduced for QEMU; their semantics are unclear and they provide a false > sense of safety. > > The last use of qatomic_mb_read() has been removed, so delete it. > qatomic_mb_set() instead can survive as an optimized > qatomic_set()+smp_mb(), similar to Linux's smp_store_mb(), but > rename it to qatomic_set_mb() to match the order of the two > operations. > > Signed-off-by: Paolo Bonzini > --- > accel/tcg/cpu-exec.c | 2 +- > accel/tcg/tcg-accel-ops-mttcg.c | 2 +- > accel/tcg/tcg-accel-ops-rr.c | 4 ++-- > docs/devel/atomics.rst | 27 ++++----------------------- > include/qemu/atomic.h | 4 ++-- > monitor/qmp.c | 2 +- > softmmu/cpus.c | 2 +- > softmmu/physmem.c | 2 +- > target/arm/hvf/hvf.c | 2 +- > tests/unit/test-aio-multithread.c | 2 +- > util/qemu-coroutine-lock.c | 4 ++-- > 11 files changed, 17 insertions(+), 36 deletions(-) Reviewed-by: Richard Henderson r~