Hi all-
AFAICT something got rather screwed up in i915 land for 4.5.
$ git log --oneline --grep='Pretend cursor is always on' v4.5 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
$ git log --oneline --grep='Pretend cursor is always on' v4.6-rc1 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2) b2435692dbb7 drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
The two patches there are almost, but not quite, the same thing, which makes me wonder how they both ended up in Linus' tree without an obvious merge conflict.
I have no idea what caused this. However, I think (on very little inspection, but it's consistent with problems I have with 4.5 on my laptop) that the first one is an *incorrect* fix for a regression in 4.5 and the second is a correct fix for the same regression. 4.6-rc1 seems okay.
I reported the regression and everyone involved has known about it for weeks. Nonetheless, 4.5 final is busted.
Can you please:
a) figure out what happened and send a backport of whatever needs to be backported to stable@vger.kernel.org.
b) do whatever needs to be done so this doesn't happen again
c) teach the i915 CI system to test Linus' tree as-is in addition to the development trees. Linus' tree and the versions of i915 in actual released versions of Linux are supposed to work.
I hate to nag, but this is at least the third time I've noticed weird release management issues in i915. I tripped on a regression a few releases ago that was known to the i915 team and fixed but the fix wasn't actually queued up for the current release. Before that, I tripped on a regression caused by an intentional behavior change that was folded in to a merge commit, making it essentially impossible to bisect and making it pointlessly hard to understand what was going on even once I found the offending code.
Thanks, Andy
On Tue, Mar 29, 2016 at 4:39 AM, Andy Lutomirski luto@amacapital.net wrote:
AFAICT something got rather screwed up in i915 land for 4.5.
$ git log --oneline --grep='Pretend cursor is always on' v4.5 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
$ git log --oneline --grep='Pretend cursor is always on' v4.6-rc1 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2) b2435692dbb7 drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
The two patches there are almost, but not quite, the same thing, which makes me wonder how they both ended up in Linus' tree without an obvious merge conflict.
I have no idea what caused this. However, I think (on very little inspection, but it's consistent with problems I have with 4.5 on my laptop) that the first one is an *incorrect* fix for a regression in 4.5 and the second is a correct fix for the same regression. 4.6-rc1 seems okay.
I reported the regression and everyone involved has known about it for weeks. Nonetheless, 4.5 final is busted.
Quoting from e2e407dc093f
"(cherry picked from commit b2435692dbb709d4c8ff3b2f2815c9b8423b72bb)"
i.e. this is intentionally twice in the history. We started to soak bugfixes in -next and then cherry pick them because we had too much fun with things blowing up, and also too much fun with really messy conflicts. It's not a botched patch in 4.5 or anything else nefarious at all.
Which just means that there's another bugfix in 4.6-rc1 that needs to be backported to 4.5 but hasn't arrived in there yet. Two possible cases: - Greg is too slow with cc: stable patches - especially around releases we occasionally put the patch into the wrong branch at first, or it simply misses the last pull. 4.6 closes for drm drivers already at 4.5-rc5, so there's a sizeable overlap where placing patches correctly requires some juggling.
- We've genuinely failed to cherry-pick a bugfix over. It happens, despite our best efforts (which of course includes running stuff on Linus' tree). Please do a reverse bisect so we know which precise commit fell through the cracks.
Thanks, Daniel
On Tue, Mar 29, 2016 at 12:43 AM, Daniel Vetter daniel.vetter@ffwll.ch wrote:
On Tue, Mar 29, 2016 at 4:39 AM, Andy Lutomirski luto@amacapital.net wrote:
AFAICT something got rather screwed up in i915 land for 4.5.
$ git log --oneline --grep='Pretend cursor is always on' v4.5 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
$ git log --oneline --grep='Pretend cursor is always on' v4.6-rc1 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2) b2435692dbb7 drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
The two patches there are almost, but not quite, the same thing, which makes me wonder how they both ended up in Linus' tree without an obvious merge conflict.
I have no idea what caused this. However, I think (on very little inspection, but it's consistent with problems I have with 4.5 on my laptop) that the first one is an *incorrect* fix for a regression in 4.5 and the second is a correct fix for the same regression. 4.6-rc1 seems okay.
I reported the regression and everyone involved has known about it for weeks. Nonetheless, 4.5 final is busted.
Quoting from e2e407dc093f
"(cherry picked from commit b2435692dbb709d4c8ff3b2f2815c9b8423b72bb)"
i.e. this is intentionally twice in the history. We started to soak bugfixes in -next and then cherry pick them because we had too much fun with things blowing up, and also too much fun with really messy conflicts. It's not a botched patch in 4.5 or anything else nefarious at all.
Bah, sorry, I read it wrong. They have the same final state but they were on different bases. I somehow reversed this in my head and thought they had the same initial state and different final states.
- We've genuinely failed to cherry-pick a bugfix over. It happens,
despite our best efforts (which of course includes running stuff on Linus' tree). Please do a reverse bisect so we know which precise commit fell through the cracks.
If I find some time, I'll try. I've already failed miserably at bisecting this thing once.
--Andy
On Tue, Mar 29, 2016 at 12:49 AM, Andy Lutomirski luto@amacapital.net wrote:
On Tue, Mar 29, 2016 at 12:43 AM, Daniel Vetter daniel.vetter@ffwll.ch wrote:
On Tue, Mar 29, 2016 at 4:39 AM, Andy Lutomirski luto@amacapital.net wrote:
AFAICT something got rather screwed up in i915 land for 4.5.
$ git log --oneline --grep='Pretend cursor is always on' v4.5 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
$ git log --oneline --grep='Pretend cursor is always on' v4.6-rc1 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2) b2435692dbb7 drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
The two patches there are almost, but not quite, the same thing, which makes me wonder how they both ended up in Linus' tree without an obvious merge conflict.
I have no idea what caused this. However, I think (on very little inspection, but it's consistent with problems I have with 4.5 on my laptop) that the first one is an *incorrect* fix for a regression in 4.5 and the second is a correct fix for the same regression. 4.6-rc1 seems okay.
I reported the regression and everyone involved has known about it for weeks. Nonetheless, 4.5 final is busted.
Quoting from e2e407dc093f
"(cherry picked from commit b2435692dbb709d4c8ff3b2f2815c9b8423b72bb)"
i.e. this is intentionally twice in the history. We started to soak bugfixes in -next and then cherry pick them because we had too much fun with things blowing up, and also too much fun with really messy conflicts. It's not a botched patch in 4.5 or anything else nefarious at all.
Bah, sorry, I read it wrong. They have the same final state but they were on different bases. I somehow reversed this in my head and thought they had the same initial state and different final states.
Also, sorry for the excessive diatribe. I plead sleepiness and mis-reading of code.
--Andy
On Tue, Mar 29, 2016 at 6:16 PM, Andy Lutomirski luto@amacapital.net wrote:
On Tue, Mar 29, 2016 at 12:49 AM, Andy Lutomirski luto@amacapital.net wrote:
On Tue, Mar 29, 2016 at 12:43 AM, Daniel Vetter daniel.vetter@ffwll.ch wrote:
On Tue, Mar 29, 2016 at 4:39 AM, Andy Lutomirski luto@amacapital.net wrote:
AFAICT something got rather screwed up in i915 land for 4.5.
$ git log --oneline --grep='Pretend cursor is always on' v4.5 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
$ git log --oneline --grep='Pretend cursor is always on' v4.6-rc1 drivers/gpu/drm/i915/ e2e407dc093f drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2) b2435692dbb7 drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)
The two patches there are almost, but not quite, the same thing, which makes me wonder how they both ended up in Linus' tree without an obvious merge conflict.
I have no idea what caused this. However, I think (on very little inspection, but it's consistent with problems I have with 4.5 on my laptop) that the first one is an *incorrect* fix for a regression in 4.5 and the second is a correct fix for the same regression. 4.6-rc1 seems okay.
I reported the regression and everyone involved has known about it for weeks. Nonetheless, 4.5 final is busted.
Quoting from e2e407dc093f
"(cherry picked from commit b2435692dbb709d4c8ff3b2f2815c9b8423b72bb)"
i.e. this is intentionally twice in the history. We started to soak bugfixes in -next and then cherry pick them because we had too much fun with things blowing up, and also too much fun with really messy conflicts. It's not a botched patch in 4.5 or anything else nefarious at all.
Bah, sorry, I read it wrong. They have the same final state but they were on different bases. I somehow reversed this in my head and thought they had the same initial state and different final states.
Also, sorry for the excessive diatribe. I plead sleepiness and mis-reading of code.
Thanks. We really appreciate friendly discussions here on intel-gfx, the technical challenges are hard enough as is. -Daniel
dri-devel@lists.freedesktop.org
-
Andy Lutomirski -
Daniel Vetter