From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4A4B58E9.4050407@domain.hid> Date: Wed, 01 Jul 2009 14:39:05 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4A48FB71.6070506@domain.hid> <4A49CD81.4060706@domain.hid> <4A49CFF0.7070202@domain.hid> <1246353623.7803.21.camel@domain.hid> <4A49D935.3060900@domain.hid> <1246353913.7803.24.camel@domain.hid> <4A49DA4E.2020604@domain.hid> <1246354047.7803.25.camel@domain.hid> <4A49DC0A.5000208@domain.hid> <4A4A391B.8000700@domain.hid> <4A4B4ED4.6020208@domain.hid> <4A4B558D.20307@domain.hid> In-Reply-To: <4A4B558D.20307@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] x86: Endless minor faults List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: xenomai-core Gilles Chanteperdrix wrote: > Jan Kiszka wrote: >> Jan Kiszka wrote: >>> It's still unclear what goes on precisely, we are still digging, but the >>> test system that can produce this is highly contended. >> Short update: Further instrumentation revealed that cr3 differs from >> active_mm->pgd while we are looping over that fault, ie. the kernel >> tries to fixup the wrong mm. And that means we have some open race >> window between updating cr3 and active_mm somewhere (isn't switch_mm run >> in a preemptible manner now?). > > Maybe the rsp is wrong and leads you to the wrong active_mm ? > >> As a first shot I disabled CONFIG_IPIPE_DELAYED_ATOMICSW, and we are now >> checking if it makes a difference. Digging deeper into the code in the >> meanwhile... > > As you have found out in the mean time, we do not use unlocked context > switches on x86. > Yes. The last question I asked myself (but couldn't answer yet due to other activity) was: Where are the local_irq_disable/enable_hw around switch_mm for its Linux callers? Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux