From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <prvs=63144aee1=Bart.VanAssche@wdc.com>
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "ming.lei@redhat.com" <ming.lei@redhat.com>
CC: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"israelr@mellanox.com" <israelr@mellanox.com>, "sagi@grimberg.me"
	<sagi@grimberg.me>, "hch@lst.de" <hch@lst.de>, "stable@vger.kernel.org"
	<stable@vger.kernel.org>, "axboe@kernel.dk" <axboe@kernel.dk>,
	"maxg@mellanox.com" <maxg@mellanox.com>, "tj@kernel.org" <tj@kernel.org>
Subject: Re: [PATCH v4] blk-mq: Fix race conditions in request timeout
 handling
Date: Tue, 10 Apr 2018 12:58:04 +0000
Message-ID: <b36ea1107be4f32fb04fffdde3ee45a2e0fcc36c.camel@wdc.com>
References: <20180410013455.7448-1-bart.vanassche@wdc.com>
	 <20180410084133.GB9133@ming.t460p>
In-Reply-To: <20180410084133.GB9133@ming.t460p>
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
List-ID: <linux-block@vger.kernel.org>

T24gVHVlLCAyMDE4LTA0LTEwIGF0IDE2OjQxICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gT24g
TW9uLCBBcHIgMDksIDIwMTggYXQgMDY6MzQ6NTVQTSAtMDcwMCwgQmFydCBWYW4gQXNzY2hlIHdy
b3RlOg0KPiA+IElmIGEgY29tcGxldGlvbiBvY2N1cnMgYWZ0ZXIgYmxrX21xX3JxX3RpbWVkX291
dCgpIGhhcyByZXNldA0KPiA+IHJxLT5hYm9ydGVkX2dzdGF0ZSBhbmQgdGhlIHJlcXVlc3QgaXMg
YWdhaW4gaW4gZmxpZ2h0IHdoZW4gdGhlIHRpbWVvdXQNCj4gDQo+IEdpdmVuIHJxLT5hYm9ydGVk
X2dzdGF0ZSBpcyByZXNldCBvbmx5IGZvciBCTEtfRUhfUkVTRVRfVElNRVIsIEkNCj4gdGhpbmsg
eW91IGFyZSBhZGRyZXNzaW5nIHRoZSByYWNlIGJldHdlZW4gbm9ybWFsIGNvbXBsZXRpb24gYW5k
DQo+IHRoZSB0aW1lb3V0IG9mIEJMS19FSF9SRVNFVF9USU1FUi4NCg0KWWVzLCB0aGF0J3MgY29y
cmVjdC4gSSB3aWxsIG1ha2UgdGhpcyBtb3JlIGV4cGxpY2l0Lg0KDQo+ID4gZXhwaXJlcyB0aGVu
IGEgcmVxdWVzdCB3aWxsIGJlIGNvbXBsZXRlZCB0d2ljZTogYSBmaXJzdCB0aW1lIGJ5IHRoZQ0K
PiA+IHRpbWVvdXQgaGFuZGxlciBhbmQgYSBzZWNvbmQgdGltZSB3aGVuIHRoZSByZWd1bGFyIGNv
bXBsZXRpb24gb2NjdXJzLg0KPiANCj4gVGhpcyBwYXRjaCBsb29rcyBzaW1wbGVyLCBhbmQgbW9y
ZSBsaWtlIHRoZSBwcmV2aW91cyBtb2RlbCBvZg0KPiB1c2luZyBibGtfbWFya19ycV9jb21wbGV0
ZSgpLg0KDQpUaGF0J3MgYWxzbyBjb3JyZWN0Lg0KDQo+IEkgaGF2ZSBvbmUgcXVlc3Rpb246DQo+
IA0KPiAtIHdpdGggdGhpcyBwYXRjaCwgcnEncyBzdGF0ZSBpcyB1cGRhdGVkIGF0b21pY2FsbHkg
YXMgY21weGNoZy4gU3VwcG9zZQ0KPiBvbmUgcnEgaXMgdGltZWQgb3V0LCB0aGUgcnEncyBzdGF0
ZSBpcyB1cGRhdGVkIGFzIE1RX1JRX0NPTVBMRVRFIGJ5DQo+IGJsa19tcV9jaGVja19leHBpcmVk
KCksIHRoZW4gb3BzLT50aW1lb3V0KCkgaXMgcnVuIGFuZA0KPiBCTEtfRUhfUkVTRVRfVElNRVIg
aXMgcmV0dXJuZWQsIHNvIGJsa19tcV9hZGRfdGltZXIocmVxLCBNUV9SUV9DT01QTEVURSwNCj4g
TVFfUlFfSU5fRkxJR0hUKSBpcyBjYWxsZWQgdG8gdXBkYXRlIHJxJ3Mgc3RhdGUgaW50byBNUV9S
UV9JTl9GTElHSFQuDQo+IA0KPiBOb3cgdGhlIG9yaWdpbmFsIG5vcm1hbCBjb21wbGV0aW9uIHN0
aWxsIG1heSBvY2N1ciBhZnRlciBycSdzIHN0YXRlDQo+IGJlY29tZXMgTVFfUlFfSU5fRkxJR0hU
LCBhbmQgc2VlbXMgdGhlcmUgaXMgc3RpbGwgdGhlIGRvdWJsZSBjb21wbGV0aW9uDQo+IHdpdGgg
dGhpcyBwYXRjaD8gTWF5YmUgSSBhbSB3cm9uZywgcGxlYXNlIGV4cGxhaW4gYSBiaXQuDQoNClRo
YXQgc2NlbmFyaW8gd29uJ3QgcmVzdWx0IGluIGEgZG91YmxlIGNvbXBsZXRpb24uIEFmdGVyIHRo
ZSB0aW1lciBoYXMNCmJlZW4gcmVzZXQgdGhlIGJsb2NrIGRyaXZlciBibGtfbXFfY29tcGxldGVf
cmVxdWVzdCgpIGNhbGwgd2lsbCBjaGFuZ2UNCnRoZSByZXF1ZXN0IHN0YXRlIGZyb20gTVFfUlFf
SU5fRkxJR0hUIGludG8gTVFfUlFfQ09NUExFVEUuIFRoZSBuZXh0DQp0aW1lIGJsa19tcV9jaGVj
a19leHBpcmVkKCkgaXMgY2FsbGVkIGl0IHdpbGwgZXhlY3V0ZSB0aGUgZm9sbG93aW5nIGNvZGU6
DQoNCglibGtfbXFfY2hhbmdlX3JxX3N0YXRlKHJxLCBNUV9SUV9JTl9GTElHSFQsIE1RX1JRX0NP
TVBMRVRFKTsNCg0KVGhhdCBmdW5jdGlvbiBjYWxsIG9ubHkgY2hhbmdlcyB0aGUgcmVxdWVzdCBz
dGF0ZSBpZiB0aGUgY3VycmVudCBzdGF0ZSBpcw0KSU5fRkxJR0hULiBIb3dldmVyLCB0aGUgYmxr
X21xX2NvbXBsZXRlX3JlcXVlc3QoKSBjYWxsIGNoYW5nZWQgdGhlIHJlcXVlc3QNCnN0YXRlIGlu
dG8gQ09NUExFVEUuIEhlbmNlLCB0aGUgYWJvdmUgYmxrX21xX2NoYW5nZV9ycV9zdGF0ZSgpIGNh
bGwgd2lsbA0KcmV0dXJuIGZhbHNlIGFuZCB0aGUgYmxrLW1xIHRpbWVvdXQgY29kZSB3aWxsIHNr
aXAgdGhpcyByZXF1ZXN0LiBJZiB0aGUNCnJlcXVlc3Qgd291bGQgYWxyZWFkeSBoYXZlIGJlZW4g
cmV1c2VkIGFuZCB3b3VsZCBoYXZlIGJlZW4gbWFya2VkIGFnYWluIGFzDQpJTl9GTElHSFQgdGhl
biBpdHMgZGVhZGxpbmUgd2lsbCBhbHNvIGhhdmUgYmVlbiB1cGRhdGVkIGFuZCB0aGUgcmVxdWVz
dA0Kd2lsbCBiZSBza2lwcGVkIGJ5IHRoZSB0aW1lb3V0IGNvZGUgYmVjYXVzZSBpdHMgZGVhZGxp
bmUgaGFzIG5vdCB5ZXQNCmV4cGlyZWQuDQoNCj4gQW5kIHN5bmNocm9uaXplX3JjdSgpIGlzIG5l
ZWRlZCBieSBUZWp1bidzIGFwcHJvYWNoIGJldHdlZW4gbWFya2luZw0KPiBDT01QTEVURSBhbmQg
aGFuZGxpbmcgdGhpcyBycSdzIHRpbWVvdXQsIGFuZCB0aGUgdGltZSBjYW4gYmUgcXVpdGUgbG9u
ZywNCj4gSSBndWVzcyBpdCBtaWdodCBiZSBlYXNpZXIgdG8gdHJpZ2dlcj8NCg0KSSBoYXZlIGRv
bmUgd2hhdCBJIGNvdWxkIHRvIHRyaWdnZXIgcmFjZXMgYmV0d2VlbiB0aGUgcmVndWxhciBjb21w
bGV0aW9uDQpwYXRoIGFuZCB0aGUgdGltZW91dCBjb2RlIGluIG15IHRlc3RzLiBXaXRob3V0IHRo
aXMgcGF0Y2ggaWYgSSBydW4gdGhlDQpzcnAtdGVzdCBzb2Z0d2FyZSBJIHNlZSBjcmFzaGVzIGJl
aW5nIHJlcG9ydGVkIGluIHRoZSByZG1hX3J4ZSBkcml2ZXIgYnV0DQp3aXRoIHRoaXMgcGF0Y2gg
YXBwbGllZCBJIGRvbid0IHNlZSBhbnkgY3Jhc2hlcyB3aXRoIG15IHRlc3RzLg0KDQpCYXJ0Lg0K
DQoNCg==