From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Bart Van Assche To: "joseph.qi@linux.alibaba.com" , "axboe@kernel.dk" CC: "gavin.dg@linux.alibaba.com" , "linux-block@vger.kernel.org" Subject: Re: [RFC] hard LOCKUP caused by race between blk_init_queue_node and blkcg_print_blkgs Date: Tue, 30 Jan 2018 21:19:30 +0000 Message-ID: <1517347168.2589.56.camel@wdc.com> References: <5ac9562b-b20a-9f5a-90c5-2187552b6f09@linux.alibaba.com> In-Reply-To: <5ac9562b-b20a-9f5a-90c5-2187552b6f09@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 List-ID: T24gVHVlLCAyMDE4LTAxLTMwIGF0IDE5OjIxICswODAwLCBKb3NlcGggUWkgd3JvdGU6DQo+IEhp IEplbnMgYW5kIEZvbGtzLA0KPiANCj4gUmVjZW50bHkgd2UndmUgZ290dGVuIGEgaGFyZCBMT0NL VVAgaXNzdWUuIEFmdGVyIGludmVzdGlnYXRpbmcgdGhlIGlzc3VlDQo+IHdlJ3ZlIGZvdW5kIGEg cmFjZSBiZXR3ZWVuIGJsa19pbml0X3F1ZXVlX25vZGUgYW5kIGJsa2NnX3ByaW50X2Jsa2dzLg0K PiBUaGUgcmFjZSBpcyBkZXNjcmliZWQgYmVsb3cuDQo+IA0KPiBibGtfaW5pdF9xdWV1ZV9ub2Rl ICAgICAgICAgICAgICAgICBibGtjZ19wcmludF9ibGtncw0KPiAgIGJsa19hbGxvY19xdWV1ZV9u b2RlICgxKQ0KPiAgICAgcS0+cXVldWVfbG9jayA9ICZxLT5fX3F1ZXVlX2xvY2sgKDIpDQo+ICAg ICBibGtjZ19pbml0X3F1ZXVlKHEpICgzKQ0KPiAgICAgICAgICAgICAgICAgICAgICAgICAgICAg ICAgICAgICBzcGluX2xvY2tfaXJxKGJsa2ctPnEtPnF1ZXVlX2xvY2spICg0KQ0KPiAgIHEtPnF1 ZXVlX2xvY2sgPSBsb2NrICg1KQ0KPiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAg ICBzcGluX3VubG9ja19pcnEoYmxrZy0+cS0+cXVldWVfbG9jaykgKDYpDQo+IA0KPiAoMSkgYWxs b2NhdGUgYW4gdW5pbml0aWFsaXplZCBxdWV1ZTsNCj4gKDIpIGluaXRpYWxpemUgcXVldWVfbG9j ayB0byBpdHMgZGVmYXVsdCBpbnRlcm5hbCBsb2NrOw0KPiAoMykgaW5pdGlhbGl6ZSBibGtjZyBw YXJ0IG9mIHJlcXVlc3QgcXVldWUsIHdoaWNoIHdpbGwgY3JlYXRlIGJsa2cgYW5kDQo+IHRoZW4g aW5zZXJ0IGl0IHRvIGJsa2dfbGlzdDsNCj4gKDQpIHRyYXZlcnNlIGJsa2dfbGlzdCBhbmQgZmlu ZCB0aGUgY3JlYXRlZCBibGtnLCBhbmQgdGhlbiB0YWtlIGl0cw0KPiBxdWV1ZSBsb2NrLCBoZXJl IGl0IGlzIHRoZSBkZWZhdWx0ICppbnRlcm5hbCBsb2NrKjsNCj4gKDUpICpyYWNlIHdpbmRvdyos IG5vdyBxdWV1ZV9sb2NrIGlzIG92ZXJyaWRkZW4gd2l0aCAqZHJpdmVyIHNwZWNpZmllZA0KPiBs b2NrKjsNCj4gKDYpIG5vdyB1bmxvY2sgKmRyaXZlciBzcGVjaWZpZWQgbG9jayosIG5vdCB0aGUg bG9ja2VkICppbnRlcm5hbCBsb2NrKiwNCj4gdW5sb2NrIGJhbGFuY2UgYnJlYWtzLg0KPiANCj4g Rm9yIHRoZSBpc3N1ZSBhYm92ZSwgSSB0aGluayBibGtjZ19pbml0X3F1ZXVlIGlzIGEgYml0IGVh cmxpZXIuIFdlDQo+IGNhbid0IGFsbG93IGEgZnVydGhlciB1c2UgYmVmb3JlIHJlcXVlc3QgcXVl dWUgaXMgZnVsbHkgaW5pdGlhbGl6ZWQuDQo+IFNpbmNlIGJsa19pbml0X3F1ZXVlX25vZGUgaXMg YSByZWFsbHkgY29tbW9uIHBhdGggYW5kIGl0IGFsbG93cyBkcml2ZXINCj4gdG8gb3ZlcnJpZGUg dGhlIGRlZmF1bHQgaW50ZXJuYWwgbG9jaywgSSdtIGFmcmFpZCBzZXZlcmFsIG90aGVyIHBsYWNl cw0KPiBtYXkgYWxzbyBoYXZlIHRoZSBzYW1lIGlzc3VlLg0KPiBBbSBJIG1pc3Npbmcgc29tZXRo aW5nIGhlcmU/DQoNCldoYXQgY29kZSB0cmlnZ2VyZWQgdGhlIGJsa2NnX3ByaW50X2Jsa2dzKCkg Y2FsbD8gV2FzIGl0IHBlcmhhcHMgYSBmdW5jdGlvbg0KcmVsYXRlZCB0byB0aHJvdHRsaW5nPyBJ ZiBzbywgSSB0aGluayB0aGVyZSBhcmUgdHdvIHBvc3NpYmxlIHdheXMgdG8gZml4IHRoaXMNCnJh Y2U6DQoxLiBNb3ZpbmcgdGhlIC5xdWV1ZV9sb2NrIGluaXRpYWxpemF0aW9uIGZyb20gYmxrX2lu aXRfcXVldWVfbm9kZSgpIGludG8NCiAgIGJsa19hbGxvY19xdWV1ZV9ub2RlKCkgc3VjaCB0aGF0 IGl0IGhhcHBlbnMgYmVmb3JlIHRoZSBibGtjZ19pbml0X3F1ZXVlKCkNCiAgIGNhbGwuIFRoaXMg aG93ZXZlciB3aWxsIHJlcXVpcmUgYSB0cmVlLXdpZGUgY2hhbmdlIG9mIHRoZSBibGtfYWxsb2Nf cXVldWUoKQ0KICAgYW5kIGFsbCBibGtfYWxsb2NfcXVldWVfbm9kZSgpIGNhbGxzIGluIGFsbCBi bG9jayBkcml2ZXJzLg0KMi4gU3BsaXR0aW5nIHRoZSBibGtfdGhyb3RsX2luaXQoKSBmdW5jdGlv biBzdWNoIHRoYXQgdGhlIGJsa2NnX2FjdGl2YXRlX3BvbGljeSgpDQogICBjYWxsIGNhbiBvY2N1 ciBhZnRlciB0aGUgLnF1ZXVlX2xvY2sgcG9pbnRlciBoYXMgYmVlbiBpbml0aWFsaXplZCwgZS5n LiBmcm9tDQogICBpbnNpZGUgYmxrX2luaXRfYWxsb2NhdGVkX3F1ZXVlKCkgb3IgZnJvbSBpbnNp ZGUgYmxrX3JlZ2lzdGVyX3F1ZXVlKCkgaW5zdGVhZA0KICAgb2YgZnJvbSBpbnNpZGUgYmxrY2df aW5pdF9xdWV1ZSgpLg0KDQpJJ20gbm90IHN1cmUgd2hhdCB0aGUgYmVzdCBhcHByb2FjaCBpcy4g TWF5YmUgdGhlcmUgaXMgZXZlbiBhIHRoaXJkIGFwcHJvYWNoDQp0aGF0IGlzIGJldHRlciB0aGFu IHRoZSB0d28gYXBwcm9hY2hlcyBtZW50aW9uZWQgYWJvdmUuDQoNCkJhcnQu