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a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1775562521; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BjVuOjI1QhnGNHiP3xYcNfuccyBOIqbuiMz0Wq5xNS4=; b=d+LPaln9yej9Cx+xdt9S0nXeZsSFTpu2HqKODSNOHXu+C+OPrPp7X1DupsRKhOJZYO/Yt1 5IQCpqI3MqLoahDg== To: litaliano00 Cc: palmer@dabbelt.com, pjw@kernel.org, aou@eecs.berkeley.edu, alex@ghiti.fr, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: Add WFI to secondary hart spinwait loop In-Reply-To: References: <20260407074534.59179-1-litaliano00.contact@gmail.com> <20260407084514.syOsks4D@linutronix.de> Date: Tue, 07 Apr 2026 13:48:41 +0200 Message-ID: <87tstnuh2e.fsf@yellow.woof> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable litaliano00 writes: > You are correct to question this. There is no interrupt sent to the > waiting harts in the current spinwait design =E2=80=94 the primary hart s= imply > writes to __cpu_spinwait_stack_pointer and __cpu_spinwait_task_pointer. > A bare WFI would cause secondary harts to sleep indefinitely since no > IPI is issued after those writes. > > The correct fix would require the primary hart to send an IPI to all > waiting harts after populating the pointers, which is a more involved > change. The current patch is insufficient as-is. Yeah, that's also what I would do. > I will send a v2 that reverts this change. Apologies for the noise. There's no need for that, this patch has not been applied. Best regards, Nam