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 17:49:25 +0100 Message-ID: <20141127174925.53e9d7a6@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> <20141127164555.4bcebfe8@thinkpad-w530> <063D6719AE5E284EB5DD2968C1650D6D1C9FDDD6@AcuExch.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1C9FDDD6@AcuExch.aculab.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Sender: "Linuxppc-dev" To: David Laight Cc: "linux-arch@vger.kernel.org" , "Michael S. Tsirkin" , Heiko Carstens , "linux-kernel@vger.kernel.org" , "mingo@kernel.org" , Christian Borntraeger , "paulus@samba.org" , "schwidefsky@de.ibm.com" , Thomas Gleixner , "linuxppc-dev@lists.ozlabs.org" , "akpm@linux-foundation.org" List-Id: linux-arch.vger.kernel.org PiBGcm9tOiBEYXZpZCBIaWxkZW5icmFuZCBbbWFpbHRvOmRhaGlAbGludXgudm5ldC5pYm0uY29t XQo+ID4gPiBGcm9tOiBEYXZpZCBIaWxkZW5icmFuZAo+ID4gPiAuLi4KPiA+ID4gPiBBbHRob3Vn aCBpdCBtaWdodCBub3QgYmUgb3B0aW1hbCwgYnV0IGtlZXBpbmcgYSBzZXBhcmF0ZSBjb3VudGVy IGZvcgo+ID4gPiA+IHBhZ2VmYXVsdF9kaXNhYmxlKCkgYXMgcGFydCBvZiB0aGUgcHJlZW1wdGlv biBjb3VudGVyIHNlZW1zIHRvIGJlIHRoZSBvbmx5Cj4gPiA+ID4gZG9hYmxlIHRoaW5nIHJpZ2h0 IG5vdy4gSSBhbSBub3Qgc3VyZSBpZiBhIGNvbXBsZXRlbHkgc2VwYXJhdGVkIGNvdW50ZXIgaXMg ZXZlbgo+ID4gPiA+IHBvc3NpYmxlLCBpbmNyZWFzaW5nIHRoZSBzaXplIG9mIHRocmVhZF9pbmZv Lgo+ID4gPgo+ID4gPiBXaGF0IGFib3V0IGFkZGluZyAoc2F5KSAweDEwMDAwIGZvciB0aGUgbW9y ZSByZXN0cmljdGl2ZSB0ZXN0Pwo+ID4gPgo+ID4gPiAJRGF2aWQKPiA+ID4KPiA+IAo+ID4gWW91 IG1lYW4gYXMgcGFydCBvZiB0aGUgcHJlZW1wdCBjb3VudGVyPwo+ID4gCj4gPiBUaGUgY3VycmVu dCBsYXlvdXQgKG9uIG15IGJyYW5jaCkgaXMKPiA+IAo+ID4gICogUFJFRU1QVF9NQVNLOiAgICAg ICAgMHgwMDAwMDBmZgo+ID4gICogU09GVElSUV9NQVNLOiAgICAgICAgMHgwMDAwZmYwMAo+ID4g ICogSEFSRElSUV9NQVNLOiAgICAgICAgMHgwMDBmMDAwMAo+ID4gICogICAgIE5NSV9NQVNLOiAg ICAgICAgMHgwMDEwMDAwMAo+ID4gICogUFJFRU1QVF9BQ1RJVkU6ICAgICAgMHgwMDIwMDAwMAo+ ID4gCj4gPiBJIHdvdWxkIGhhdmUgYWRkZWQKPiA+ICAqIFBBR0VGQVVMVF9NQVNLOiAgICAgIDB4 MDNDMDAwMDAKPiAKPiBJJ20gbm90IHN1cmUgd2hlcmUgeW91J2QgbmVlZCB0byBhZGQgdGhlIGJp dHMuCj4gCj4gSSB0aGluayB0aGUgYWJvdmUgd29ya3MgYmVjYXVzZSBkaXNhYmxpbmcgJ0hBUkRJ UlEnIGltcGxpY2l0bHkKPiBkaXNhYmxlcyAnU09GVElSUScgYW5kICdQUkVFTVBUJyAoZXRjKSwg c28gaWYgMjU2KyB0aHJlYWRzCj4gZGlzYWJsZSBQUkVFTVBUIGV2ZXJ5dGhpbmcgc3RpbGwgd29y a3MuCgpBRkFJSyAyNTYrIGxldmVscyBvZiBwcmVlbXB0IHdpbGwgYnJlYWsgdGhlIHN5c3RlbSA6 KQoKVGhlcmVmb3JlIHdpdGggQ09ORklHX0RFQlVHX1BSRUVNUFQgd2UgdmVyaWZ5IHRoYXQgd2Ug ZG9uJ3QgaGF2ZSBhbnkKb3Zlci91bmRlcmZsb3dzLgoKQnV0IHN1Y2ggYnVncyBjYW4gb25seSBi ZSBmb3VuZCB3aXRoIENPTkZJR19ERUJVR19QUkVFTVBUIGVuYWJsZWQuCgo+IAo+IFNvIGlmIGRp c2FibGluZyBwYWdlZmF1bHRzIGltcGxpZXMgdGhhdCBwcmUtZW1wdGlvbiBpcyBkaXNhYmxlZAo+ IChidXQgU09GVElSUSBpcyBzdGlsbCBhbGxvd2VkKSB0aGVuIHlvdSBuZWVkIHRvIGluc2VydCB5 b3VyIGJpdChzKQo+IGJldHdlZW4gMHhmZjAwIGFuZCAweDAwZmYuCj4gT1RPSCBpZiBkaXNhYmxp bmcgcHJlLWVtcHRpb24gaW1wbGllcyB0aGF0IHBhZ2VmYXVsdHMgYXJlIGRpc2FibGVkCj4gdGhl biB5b3UnZCBuZWVkIHRvIHVzZSB0aGUgbHNiIGFuZCBjaGFuZ2UgYWxsIHRoZSBhYm92ZSB2YWx1 ZXMuCj4gCj4gV2hpY2ggbWFrZXMgbWUgdGhpbmsgdGhhdCAnUFJFRU1QVF9BQ1RJVkUnIGlzbid0 IHJpZ2h0IGF0IGFsbC4KPiBUd28gdGhyZWFkcyBkaXNhYmxpbmcgTk1JcyAob3IgMzIgIGRpc2Fi bGluZyBIQVJESVJRKSB3b24ndCBEVFJULgoKV2l0aCB0aHJlYWRzIHlvdSBtZWFuIGxldmVscz8g VGhpcyBpcyBhIHBlciB0aHJlYWQgaW5mb3JtYXRpb24uCgo+IAo+IE9UT0ggSSdtIG9ubHkgZ3Vl c3NpbmcgYXQgaG93IHRoaXMgaXMgdXNlZC4KPiAKPiAJRGF2aWQKPiAKPiAKPiAKCl9fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCkxpbnV4cHBjLWRldiBtYWls aW5nIGxpc3QKTGludXhwcGMtZGV2QGxpc3RzLm96bGFicy5vcmcKaHR0cHM6Ly9saXN0cy5vemxh YnMub3JnL2xpc3RpbmZvL2xpbnV4cHBjLWRldg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:54700 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751490AbaK0Qt5 (ORCPT ); Thu, 27 Nov 2014 11:49:57 -0500 Received: from /spool/local by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Nov 2014 16:49:55 -0000 Date: Thu, 27 Nov 2014 17:49:25 +0100 From: David Hildenbrand Subject: Re: [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic Message-ID: <20141127174925.53e9d7a6@thinkpad-w530> In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1C9FDDD6@AcuExch.aculab.com> 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> <20141127164555.4bcebfe8@thinkpad-w530> <063D6719AE5E284EB5DD2968C1650D6D1C9FDDD6@AcuExch.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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" Message-ID: <20141127164925.cxvCz_TTmWhPlMNJXOks5WdiNR2AhITIiO42PaNLvwU@z> > From: David Hildenbrand [mailto:dahi@linux.vnet.ibm.com] > > > 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 > > I'm not sure where you'd need to add the bits. > > I think the above works because disabling 'HARDIRQ' implicitly > disables 'SOFTIRQ' and 'PREEMPT' (etc), so if 256+ threads > disable PREEMPT everything still works. AFAIK 256+ levels of preempt will break the system :) Therefore with CONFIG_DEBUG_PREEMPT we verify that we don't have any over/underflows. But such bugs can only be found with CONFIG_DEBUG_PREEMPT enabled. > > So if disabling pagefaults implies that pre-emption is disabled > (but SOFTIRQ is still allowed) then you need to insert your bit(s) > between 0xff00 and 0x00ff. > OTOH if disabling pre-emption implies that pagefaults are disabled > then you'd need to use the lsb and change all the above values. > > Which makes me think that 'PREEMPT_ACTIVE' isn't right at all. > Two threads disabling NMIs (or 32 disabling HARDIRQ) won't DTRT. With threads you mean levels? This is a per thread information. > > OTOH I'm only guessing at how this is used. > > David > > >