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[174.21.71.127]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21da414c483sm85530395ad.159.2025.01.28.11.44.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Jan 2025 11:44:06 -0800 (PST) Message-ID: Date: Tue, 28 Jan 2025 11:44:04 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/9] accel/tcg: Simplify use of &first_cpu in rr_cpu_thread_fn() To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Cc: Peter Maydell , Yanan Wang , Eduardo Habkost , Harsh Prateek Bora , kvm@vger.kernel.org, Zhao Liu , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Markus Armbruster , Igor Mammedov , Marcel Apfelbaum , Peter Xu , Paolo Bonzini References: <20250128142152.9889-1-philmd@linaro.org> <20250128142152.9889-2-philmd@linaro.org> Content-Language: en-US From: Richard Henderson In-Reply-To: <20250128142152.9889-2-philmd@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::632; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x632.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, 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 1/28/25 06:21, Philippe Mathieu-Daudé wrote: > Let vCPUs wait for themselves being ready first, then other ones. > This allows the first thread to starts without the global vcpu > queue (thus &first_cpu) being populated. > > Signed-off-by: Philippe Mathieu-Daudé > --- > accel/tcg/tcg-accel-ops-rr.c | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/accel/tcg/tcg-accel-ops-rr.c b/accel/tcg/tcg-accel-ops-rr.c > index 028b385af9a..5ad3d617bce 100644 > --- a/accel/tcg/tcg-accel-ops-rr.c > +++ b/accel/tcg/tcg-accel-ops-rr.c > @@ -197,20 +197,21 @@ static void *rr_cpu_thread_fn(void *arg) > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > /* wait for initial kick-off after machine start */ > - while (first_cpu->stopped) { > - qemu_cond_wait_bql(first_cpu->halt_cond); > + while (cpu->stopped) { > + CPUState *iter_cpu; > + > + qemu_cond_wait_bql(cpu->halt_cond); > > /* process any pending work */ > - CPU_FOREACH(cpu) { > - current_cpu = cpu; > - qemu_wait_io_event_common(cpu); > + CPU_FOREACH(iter_cpu) { > + current_cpu = iter_cpu; > + qemu_wait_io_event_common(iter_cpu); > } > } > > + g_assert(first_cpu); > rr_start_kick_timer(); > > - cpu = first_cpu; This final line seems to be unrelated. I'm not saying it's wrong, but it's certainly a change in behaviour. We no longer execute from first_cpu first. r~