From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic Date: Thu, 27 Nov 2014 16:45:55 +0100 Message-ID: <20141127164555.4bcebfe8@thinkpad-w530> References: <20141126151729.GB9612@redhat.com> <20141126152334.GA9648@redhat.com> <20141126163207.63810fcb@thinkpad-w530> <20141126154717.GB10568@redhat.com> <5475FAB1.1000802@de.ibm.com> <20141126163216.GB10850@redhat.com> <547604FC.4030300@de.ibm.com> <20141126170447.GC11202@redhat.com> <20141127070919.GA4390@osiris> <20141127090301.3ddc3077@thinkpad-w530> <20141127120441.GB4390@osiris> <20141127161905.7c6220ee@thinkpad-w530> <063D6719AE5E284EB5DD2968C1650D6D1C9FDD6A@AcuExch.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:49771 "EHLO e06smtp17.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750957AbaK0PqK (ORCPT ); Thu, 27 Nov 2014 10:46:10 -0500 Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Nov 2014 15:46:09 -0000 In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1C9FDD6A@AcuExch.aculab.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Laight Cc: Thomas Gleixner , "linux-arch@vger.kernel.org" , "Michael S. Tsirkin" , Heiko Carstens , "linux-kernel@vger.kernel.org" , Christian Borntraeger , "paulus@samba.org" , "schwidefsky@de.ibm.com" , "akpm@linux-foundation.org" , "linuxppc-dev@lists.ozlabs.org" , "mingo@kernel.org" > From: David Hildenbrand > ... > > Although it might not be optimal, but keeping a separate counter for > > pagefault_disable() as part of the preemption counter seems to be the only > > doable thing right now. I am not sure if a completely separated counter is even > > possible, increasing the size of thread_info. > > What about adding (say) 0x10000 for the more restrictive test? > > David > You mean as part of the preempt counter? The current layout (on my branch) is * PREEMPT_MASK: 0x000000ff * SOFTIRQ_MASK: 0x0000ff00 * HARDIRQ_MASK: 0x000f0000 * NMI_MASK: 0x00100000 * PREEMPT_ACTIVE: 0x00200000 I would have added * PAGEFAULT_MASK: 0x03C00000 So 4 bit == 16 levels (tbd) By implementing scope checks in the debug case like done for the regular preempt_count_inc() preempt_count_dec(), we could catch over/underflows. Thanks, David