From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Brodkin Subject: Re: Do we need to disable preemption in flush_tlb_range()? Date: Fri, 16 Mar 2018 15:01:22 +0000 Message-ID: <1521212481.4805.2.camel@synopsys.com> References: <1519917189.13866.6.camel@synopsys.com> <5a5c67c1-9f45-f908-2c8d-0914cd616a18@synopsys.com> <20180315082720.GT4064@hirez.programming.kicks-ass.net> <1521106770.11552.70.camel@synopsys.com> <20180316101124.GB4064@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20180316101124.GB4064@hirez.programming.kicks-ass.net> Content-Language: en-US Content-ID: <44DB983CB1008B4F89AD99B8A38C0138@internal.synopsys.com> Sender: linux-kernel-owner@vger.kernel.org To: "peterz@infradead.org" Cc: "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Vineet.Gupta1@synopsys.com" , "linux-snps-arc@lists.infradead.org" List-Id: linux-arch.vger.kernel.org SGkgUGV0ZXIsDQoNCk9uIEZyaSwgMjAxOC0wMy0xNiBhdCAxMToxMSArMDEwMCwgUGV0ZXIgWmlq bHN0cmEgd3JvdGU6DQo+IE9uIFRodSwgTWFyIDE1LCAyMDE4IGF0IDA5OjM5OjMxQU0gKzAwMDAs IEFsZXhleSBCcm9ka2luIHdyb3RlOg0KPiA+IEhpIFBldGVyLA0KPiA+IA0KPiA+IE9uIFRodSwg MjAxOC0wMy0xNSBhdCAwOToyNyArMDEwMCwgUGV0ZXIgWmlqbHN0cmEgd3JvdGU6DQo+ID4gPiBP biBXZWQsIE1hciAxNCwgMjAxOCBhdCAwMToxOTowMVBNIC0wNzAwLCBWaW5lZXQgR3VwdGEgd3Jv dGU6DQo+ID4gPiA+ICtDQyBQZXRlciBzaW5jZSB3ZSBoYXZlIGhpcyBhdHRlbnRpb24gOy0pDQo+ ID4gPiANCj4gPiA+IFllYWgsIHRpbWV6b25lIGNvbGxpc2lvbiB0aGVyZSwgSSB0eXBpY2FsbHkg c2xlZXAgYXQgMWFtIDstKQ0KPiA+ID4gDQo+ID4gPiA+IE9uIDAzLzAxLzIwMTggMDc6MTMgQU0s IEFsZXhleSBCcm9ka2luIHdyb3RlOg0KPiA+ID4gPiA+IEhpIFZpbmVldCwNCj4gPiA+ID4gPiAN Cj4gPiA+ID4gPiBKdXN0IG5vdGljZWQgdGhhdCBpbiBjb21tZW50cyBmb3Igc21wX2NhbGxfZnVu Y3Rpb25fbWFueSgpIGl0IGlzIHNhaWQgdGhhdA0KPiA+ID4gPiA+IHByZWVtcHRpb24gbXVzdCBi ZSBkaXNhYmxlZCBkdXJpbmcgaXRzIGV4ZWN1dGlvbi4gQW5kIHRoYXQgZnVuY3Rpb24gZ2V0cyBl eGVjdXRlZA0KPiA+ID4gPiA+IGFtb25nIG90aGVyIHdheXMgbGlrZSB0aGF0Og0KPiA+ID4gPiA+ IC0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tPjgtLS0tLS0tLS0tLS0tLS0tLS0tLS0tLQ0KPiA+ ID4gPiA+ICAgIGZsdXNoX3RsYl9yYW5nZSgpDQo+ID4gPiA+ID4gICAgICAtPiBvbl9lYWNoX2Nw dV9tYXNrKCkNCj4gPiA+ID4gPiAgICAgICAgICAgLT4gc21wX2NhbGxfZnVuY3Rpb25fbWFueSgp DQo+ID4gPiA+ID4gLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0+OC0tLS0tLS0tLS0tLS0tLS0t LS0tLS0tDQo+ID4gPiA+IA0KPiA+ID4gPiBJbiBnZW5lcmFsIEkgcHJlZmVyIG5vdCB0byAtIFBl dGVyIHdoYXQgc2F5IHlvdSA/DQo+ID4gPiANCj4gPiA+IFRoZSBjb21tZW50IHdpdGggc21wX2Nh bGxfZnVuY3Rpb25fbWFueSgpIGlzIGNvcnJlY3QsIGl0IHJlbGllcyBvbg0KPiA+ID4gcHJlZW1w dGlvbiBiZWluZyBkaXNhYmxlZCBpbiBhIG51bWJlciBvZiB3YXlzLiBJIHdvdWxkIGV4cGVjdA0K PiA+ID4gdGhpc19jcHVfcHRyKCkgZm9yIGV4YW1wbGUgdG8gY29tcGxhaW4gd2hlbiB1c2VkIHdp dGggcHJlZW1wdGlvbg0KPiA+ID4gZW5hYmxlZCAoQ09ORklHX0RFQlVHX1BSRUVNUFQpLg0KPiAN Cj4gU28gb25fZWFjaF9jcHVfbWFzaygpIGFscmVhZHkgZGlzYWJsZXMgcHJlZW1wdGlvbiBhcm91 bmQgY2FsbGluZw0KPiBzbXBfY2FsbF9mdW5jdGlvbl9tYW55KCkuDQoNClJpZ2h0IHRoYXQgaGFw cGVucyBpbiBnZXRfY3B1KCkgc28gdGhlbiB3ZSdyZSBnb2xkZW4gaGVyZS4NClRoYW5rcyBmb3Ig cG9pbnRpbmcgb3V0IC0gd2FzIG5vdCBjbGVhciBpbW1lZGlhdGVseSBmcm9tIHRoZSBjb2RlIDop DQoNCi1BbGV4ZXk= From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey.Brodkin@synopsys.com (Alexey Brodkin) Date: Fri, 16 Mar 2018 15:01:22 +0000 Subject: Do we need to disable preemption in flush_tlb_range()? In-Reply-To: <20180316101124.GB4064@hirez.programming.kicks-ass.net> References: <1519917189.13866.6.camel@synopsys.com> <5a5c67c1-9f45-f908-2c8d-0914cd616a18@synopsys.com> <20180315082720.GT4064@hirez.programming.kicks-ass.net> <1521106770.11552.70.camel@synopsys.com> <20180316101124.GB4064@hirez.programming.kicks-ass.net> List-ID: Message-ID: <1521212481.4805.2.camel@synopsys.com> To: linux-snps-arc@lists.infradead.org Hi Peter, On Fri, 2018-03-16@11:11 +0100, Peter Zijlstra wrote: > On Thu, Mar 15, 2018@09:39:31AM +0000, Alexey Brodkin wrote: > > Hi Peter, > > > > On Thu, 2018-03-15@09:27 +0100, Peter Zijlstra wrote: > > > On Wed, Mar 14, 2018@01:19:01PM -0700, Vineet Gupta wrote: > > > > +CC Peter since we have his attention ;-) > > > > > > Yeah, timezone collision there, I typically sleep at 1am ;-) > > > > > > > On 03/01/2018 07:13 AM, Alexey Brodkin wrote: > > > > > Hi Vineet, > > > > > > > > > > Just noticed that in comments for smp_call_function_many() it is said that > > > > > preemption must be disabled during its execution. And that function gets executed > > > > > among other ways like that: > > > > > -------------------------->8----------------------- > > > > > flush_tlb_range() > > > > > -> on_each_cpu_mask() > > > > > -> smp_call_function_many() > > > > > -------------------------->8----------------------- > > > > > > > > In general I prefer not to - Peter what say you ? > > > > > > The comment with smp_call_function_many() is correct, it relies on > > > preemption being disabled in a number of ways. I would expect > > > this_cpu_ptr() for example to complain when used with preemption > > > enabled (CONFIG_DEBUG_PREEMPT). > > So on_each_cpu_mask() already disables preemption around calling > smp_call_function_many(). Right that happens in get_cpu() so then we're golden here. Thanks for pointing out - was not clear immediately from the code :) -Alexey