From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.fireflyinternet.com ([109.228.58.192]:60949 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752097AbdC0LAT (ORCPT ); Mon, 27 Mar 2017 07:00:19 -0400 Date: Mon, 27 Mar 2017 12:00:04 +0100 From: Chris Wilson To: Mika Kuoppala Cc: intel-gfx@lists.freedesktop.org, "# v4 . 10+" Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: Wrap tail pointer after reset tweaking Message-ID: <20170327110004.GF10606@nuc-i3427.alporthouse.com> References: <20170327032815.19504-1-chris@chris-wilson.co.uk> <87fuhzxamn.fsf@gaia.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87fuhzxamn.fsf@gaia.fi.intel.com> Sender: stable-owner@vger.kernel.org List-ID: On Mon, Mar 27, 2017 at 01:44:00PM +0300, Mika Kuoppala wrote: > Chris Wilson writes: > > > If the request->wa_tail is 0 (because it landed exactly on the end of > > the ringbuffer), when we reconstruct request->tail following a reset we > > fill in an illegal value (-8 or 0x001ffff8). As a result, RING_HEAD is > > never able to catch up with RING_TAIL and the GPU spins endlessly. If > > the ring contains a couple of breadcrumbs, even our hangcheck is unable > > to catch the busy-looping as the ACTHD and seqno continually advance. > > Tail is past ring size (on hw) and the ring contents has seqno writes. > So we will replay the ring contents over and over and seqno advances > and wraps back to the first breadcrumbs in ring? Yup. It was most confusing to watch. The execlist_port[] was static, RING_START was static, yet the seqno kept changing. I felt like I was hallucinating. That or insomnia. -Chris -- Chris Wilson, Intel Open Source Technology Centre From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wilson Subject: Re: [PATCH 1/2] drm/i915/execlists: Wrap tail pointer after reset tweaking Date: Mon, 27 Mar 2017 12:00:04 +0100 Message-ID: <20170327110004.GF10606@nuc-i3427.alporthouse.com> References: <20170327032815.19504-1-chris@chris-wilson.co.uk> <87fuhzxamn.fsf@gaia.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id B0C486E1AB for ; Mon, 27 Mar 2017 11:00:21 +0000 (UTC) Content-Disposition: inline In-Reply-To: <87fuhzxamn.fsf@gaia.fi.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Mika Kuoppala Cc: intel-gfx@lists.freedesktop.org, "# v4 . 10+" List-Id: intel-gfx@lists.freedesktop.org T24gTW9uLCBNYXIgMjcsIDIwMTcgYXQgMDE6NDQ6MDBQTSArMDMwMCwgTWlrYSBLdW9wcGFsYSB3 cm90ZToKPiBDaHJpcyBXaWxzb24gPGNocmlzQGNocmlzLXdpbHNvbi5jby51az4gd3JpdGVzOgo+ IAo+ID4gSWYgdGhlIHJlcXVlc3QtPndhX3RhaWwgaXMgMCAoYmVjYXVzZSBpdCBsYW5kZWQgZXhh Y3RseSBvbiB0aGUgZW5kIG9mCj4gPiB0aGUgcmluZ2J1ZmZlciksIHdoZW4gd2UgcmVjb25zdHJ1 Y3QgcmVxdWVzdC0+dGFpbCBmb2xsb3dpbmcgYSByZXNldCB3ZQo+ID4gZmlsbCBpbiBhbiBpbGxl Z2FsIHZhbHVlICgtOCBvciAweDAwMWZmZmY4KS4gQXMgYSByZXN1bHQsIFJJTkdfSEVBRCBpcwo+ ID4gbmV2ZXIgYWJsZSB0byBjYXRjaCB1cCB3aXRoIFJJTkdfVEFJTCBhbmQgdGhlIEdQVSBzcGlu cyBlbmRsZXNzbHkuIElmCj4gPiB0aGUgcmluZyBjb250YWlucyBhIGNvdXBsZSBvZiBicmVhZGNy dW1icywgZXZlbiBvdXIgaGFuZ2NoZWNrIGlzIHVuYWJsZQo+ID4gdG8gY2F0Y2ggdGhlIGJ1c3kt bG9vcGluZyBhcyB0aGUgQUNUSEQgYW5kIHNlcW5vIGNvbnRpbnVhbGx5IGFkdmFuY2UuCj4gCj4g VGFpbCBpcyBwYXN0IHJpbmcgc2l6ZSAob24gaHcpIGFuZCB0aGUgcmluZyBjb250ZW50cyBoYXMg c2Vxbm8gd3JpdGVzLgo+IFNvIHdlIHdpbGwgcmVwbGF5IHRoZSByaW5nIGNvbnRlbnRzIG92ZXIg YW5kIG92ZXIgYW5kIHNlcW5vIGFkdmFuY2VzCj4gYW5kIHdyYXBzIGJhY2sgdG8gdGhlIGZpcnN0 IGJyZWFkY3J1bWJzIGluIHJpbmc/CgpZdXAuIEl0IHdhcyBtb3N0IGNvbmZ1c2luZyB0byB3YXRj aC4gVGhlIGV4ZWNsaXN0X3BvcnRbXSB3YXMgc3RhdGljLApSSU5HX1NUQVJUIHdhcyBzdGF0aWMs IHlldCB0aGUgc2Vxbm8ga2VwdCBjaGFuZ2luZy4gSSBmZWx0IGxpa2UgSSB3YXMKaGFsbHVjaW5h dGluZy4gVGhhdCBvciBpbnNvbW5pYS4KLUNocmlzCgotLSAKQ2hyaXMgV2lsc29uLCBJbnRlbCBP cGVuIFNvdXJjZSBUZWNobm9sb2d5IENlbnRyZQpfX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fXwpJbnRlbC1nZnggbWFpbGluZyBsaXN0CkludGVsLWdmeEBsaXN0 cy5mcmVlZGVza3RvcC5vcmcKaHR0cHM6Ly9saXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9s aXN0aW5mby9pbnRlbC1nZngK