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[174.21.142.130]) by smtp.gmail.com with ESMTPSA id x23-20020a63fe57000000b0036490068f12sm14544413pgj.90.2022.03.13.21.36.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 13 Mar 2022 21:36:57 -0700 (PDT) Message-ID: Date: Sun, 13 Mar 2022 21:36:55 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: Question about atomics Content-Language: en-US To: Warner Losh References: <5bb620d4-96f0-cf7f-5530-af529a32c78d@linaro.org> <45371f77-cae6-bf96-802d-6a3e70d5e334@linaro.org> From: Richard Henderson In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::1029 (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::1029; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x1029.google.com X-Spam_score_int: -6 X-Spam_score: -0.7 X-Spam_bar: / X-Spam_report: (-0.7 / 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=-0.001, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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: , Cc: Paolo Bonzini , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/13/22 21:09, Warner Losh wrote: > Oh? Out of paranoia, how can I verify that this is the case when compiled on FreeBSD? > Perhaps the atomic sequence FreeBSD uses differs a little from Linux and we don't trigger > that code? $ objdump -dr libqemu-arm-*-user.fa.p/accel_tcg_user-exec.c.o 0000000000001490 : ... 14b7: e8 04 ec ff ff callq c0 14bc: 48 89 c2 mov %rax,%rdx 14bf: 44 89 e0 mov %r12d,%eax 14c2: f0 44 0f b1 32 lock cmpxchg %r14d,(%rdx) r~