lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <27240C0AC20F114CBF8149A2696CBE4A01E5B762@SHSMSX101.ccr.corp.intel.com> Date: Thu, 14 Aug 2014 14:26:38 +0000 From: "Liu, Chuansheng" <chuansheng.liu@...el.com> To: Daniel Lezcano <daniel.lezcano@...aro.org>, Peter Zijlstra <peterz@...radead.org> CC: "Rafael J. Wysocki" <rjw@...ysocki.net>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, "Liu, Changcheng" <changcheng.liu@...el.com>, "Wang, Xiaoming" <xiaoming.wang@...el.com>, "Chakravarty, Souvik K" <souvik.k.chakravarty@...el.com> Subject: RE: [PATCH] cpuidle: Fix the CPU stuck at C0 for 2-3s after PM_QOS back to DEFAULT > -----Original Message----- > From: Daniel Lezcano [mailto:daniel.lezcano@...aro.org] > Sent: Thursday, August 14, 2014 10:17 PM > To: Liu, Chuansheng; Peter Zijlstra > Cc: Rafael J. Wysocki; linux-pm@...r.kernel.org; LKML; Liu, Changcheng; > Wang, Xiaoming; Chakravarty, Souvik K > Subject: Re: [PATCH] cpuidle: Fix the CPU stuck at C0 for 2-3s after PM_QOS > back to DEFAULT > > On 08/14/2014 04:10 PM, Liu, Chuansheng wrote: > > > > > >> -----Original Message----- > >> From: Peter Zijlstra [mailto:peterz@...radead.org] > >> Sent: Thursday, August 14, 2014 9:13 PM > >> To: Liu, Chuansheng > >> Cc: Daniel Lezcano; Rafael J. Wysocki; linux-pm@...r.kernel.org; LKML; Liu, > >> Changcheng; Wang, Xiaoming; Chakravarty, Souvik K > >> Subject: Re: [PATCH] cpuidle: Fix the CPU stuck at C0 for 2-3s after PM_QOS > >> back to DEFAULT > >> > >> On Thu, Aug 14, 2014 at 11:24:06AM +0000, Liu, Chuansheng wrote: > >>> If inspecting the polling flag, we can not fix the race between poll_idle and > >> smp_callback, > >>> since in poll_idle(), before set polling flag, if the smp_callback come in, then > >> no resched bit set, > >>> after that, poll_idle() will do the polling action, without reselection > >> immediately, it will bring power > >>> regression here. > >> > >> -ENOPARSE. Is there a question there? > > > > Lezcano suggest to inspect the polling flag, then code is like below: > > smp_callback() { > > if (polling_flag) > > set_resched_bit; > > } > > > > And the poll_idle code is like below: > > static int poll_idle(struct cpuidle_device *dev, > > struct cpuidle_driver *drv, int index) > > { > > local_irq_enable(); > > if (!current_set_polling_and_test()) { > > while (!need_resched()) > > Or alternatively, something like: > > while (!need_resched() || kickme) { > ... > } > > > smp_callback() > { > kickme = 1; > } > > kickme is a percpu variable and set to zero when exiting the 'enter' > callback. > > So we don't mess with the polling flag, which is already a bit tricky. > > This patch is very straightforward to illustrate the idea. > > > cpu_relax(); > > } > > current_clr_polling(); > > > > return index; > > } > > Thanks Lezcano, the new flag kickme sounds making things simple, will try to send one new patch to review:)
Powered by blists - more mailing lists