From mboxrd@z Thu Jan 1 00:00:00 1970 From: f.fainelli@gmail.com (Florian Fainelli) Date: Thu, 27 Jul 2017 13:07:00 -0700 Subject: halting the kernel does not stop the CPU cores? In-Reply-To: References: Message-ID: <26ccb0f7-0f78-27cd-cead-ddd810f4a33e@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 07/27/2017 07:38 AM, Heinz Wrobel wrote: > Hi, > > I noticed that when halting the kernel (intentionally or not), the cores effectively go into a while(1) loop and power consumption on larger devices really jumps up significantly to the point where, e.g., a ?crash? turns into ?crash and burn?. > > I would assume that if a system is halted, you don?t want to dissipate more power than on a running system but go as silent as low power as reasonable. > > Is there any specific reason why the cores would not go into a wfi loop like they do on idle? > The patch to fix this seems to be easy at first glance, but is there a good reason *NOT* to do such a patch and to leave the plain while(1)? In fact, if your platform supports CPU_HOTPLUG, I am not clear why smp_send_stop() + ipi_send_stop() is not calling platform_cpu_kill() which would be smp_ops.cpu_kill() but instead cpu_relax() was chosen? The CPU is dead anyway so as you say, so it's not like there is a remote chance to resume execution on these secondary cores? -- Florian