Regression on linux-next (next-20260324 )

Regression on linux-next (next-20260324 )

[Borah, Chaitanya Kumar]

Hello Matthew,

Hope you are doing well. I am Chaitanya from the linux graphics team in 
Intel.

This mail is regarding a regression we are seeing in our CI runs[1] on
linux-next repository.

Since the version next-20260324 [2], we are seeing the following regression

`````````````````````````````````````````````````````````````````````````````````
<5>[  157.361977] [IGT] Inactivity timeout exceeded. Killing the current 
test with SIGQUIT.
<6>[  157.362097] sysrq: HELP : loglevel(0-9) reboot(b) crash(c) 
show-all-locks(d) terminate-all-tasks(e) memory-full-oom-kill(f) 
kill-all-tasks(i) thaw-filesystems(j) sak(k) 
show-backtrace-all-active-cpus(l) show-memory-usage(m) 
nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) 
unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(v) 
show-blocked-tasks(w) dump-ftrace-buffer(z) replay-kernel-logs(R)
<6>[  157.399543] sysrq: Show State
<6>[  157.403061] task:systemd         state:S stack:0     pid:1 
tgid:1     ppid:0      task_flags:0x400100 flags:0x00080000
<6>[  157.403067] Call Trace:
<6>[  157.403069]  <TASK>
<6>[  157.403072]  __schedule+0x5d7/0x1ef0
<6>[  157.403078]  ? lock_acquire+0xc4/0x300
<6>[  157.403084]  ? schedule+0x10e/0x180
<6>[  157.403087]  ? lock_release+0xcd/0x2b0
<6>[  157.403092]  schedule+0x3a/0x180
<6>[  157.403094]  schedule_hrtimeout_range_clock+0x112/0x120
<6>[  157.403097]  ? do_epoll_wait+0x3e4/0x5b0
<6>[  157.403102]  ? lock_release+0xcd/0x2b0
<6>[  157.403104]  ? _raw_spin_unlock_irq+0x27/0x70
<6>[  157.403106]  ? do_epoll_wait+0x3e4/0x5b0
<6>[  157.403110]  schedule_hrtimeout_range+0x13/0x30
`````````````````````````````````````````````````````````````````````````````````
Details log can be found in [3].

After bisecting the tree, the following patch [4] seems to be the first 
"bad" commit

`````````````````````````````````````````````````````````````````````````````````````````````````````````
commit 25500ba7e77ce9d3d9b5a1929d41a2ee2e23f6fe
Author: Matthew Wilcox (Oracle) willy@infradead.org
Date:   Thu Mar 5 19:55:43 2026 +0000

     locking/mutex: Remove the list_head from struct mutex
`````````````````````````````````````````````````````````````````````````````````````````````````````````

We could not revert the patch because of merge conflict but resetting to 
the parent of the commit seems to fix the issue.

Could you please check why the patch causes this regression and provide 
a fix if necessary?

Thank you.

Regards

Chaitanya

[1]
https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html?
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20260324
[3]
https://intel-gfx-ci.01.org/tree/linux-next/next-20260326/bat-arlh-2/dmesg0.txt
[4] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20231130&id=f4acfcd4deb158b96595250cc332901b282d15b0

Re: Regression on linux-next (next-20260324 )

[Peter Zijlstra]

On Fri, Mar 27, 2026 at 07:09:26PM +0530, Borah, Chaitanya Kumar wrote:
> Hello Matthew,
> 
> Hope you are doing well. I am Chaitanya from the linux graphics team in
> Intel.
> 
> This mail is regarding a regression we are seeing in our CI runs[1] on
> linux-next repository.
> 
> Since the version next-20260324 [2], we are seeing the following regression
> 
> `````````````````````````````````````````````````````````````````````````````````
> <5>[  157.361977] [IGT] Inactivity timeout exceeded. Killing the current
> test with SIGQUIT.
> <6>[  157.362097] sysrq: HELP : loglevel(0-9) reboot(b) crash(c)
> show-all-locks(d) terminate-all-tasks(e) memory-full-oom-kill(f)
> kill-all-tasks(i) thaw-filesystems(j) sak(k)
> show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n)
> poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s)
> show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w)
> dump-ftrace-buffer(z) replay-kernel-logs(R)
> <6>[  157.399543] sysrq: Show State
> <6>[  157.403061] task:systemd         state:S stack:0     pid:1 tgid:1
> ppid:0      task_flags:0x400100 flags:0x00080000
> <6>[  157.403067] Call Trace:
> <6>[  157.403069]  <TASK>
> <6>[  157.403072]  __schedule+0x5d7/0x1ef0
> <6>[  157.403078]  ? lock_acquire+0xc4/0x300
> <6>[  157.403084]  ? schedule+0x10e/0x180
> <6>[  157.403087]  ? lock_release+0xcd/0x2b0
> <6>[  157.403092]  schedule+0x3a/0x180
> <6>[  157.403094]  schedule_hrtimeout_range_clock+0x112/0x120
> <6>[  157.403097]  ? do_epoll_wait+0x3e4/0x5b0
> <6>[  157.403102]  ? lock_release+0xcd/0x2b0
> <6>[  157.403104]  ? _raw_spin_unlock_irq+0x27/0x70
> <6>[  157.403106]  ? do_epoll_wait+0x3e4/0x5b0
> <6>[  157.403110]  schedule_hrtimeout_range+0x13/0x30
> `````````````````````````````````````````````````````````````````````````````````
> Details log can be found in [3].
> 
> After bisecting the tree, the following patch [4] seems to be the first
> "bad" commit
> 
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> commit 25500ba7e77ce9d3d9b5a1929d41a2ee2e23f6fe
> Author: Matthew Wilcox (Oracle) willy@infradead.org
> Date:   Thu Mar 5 19:55:43 2026 +0000
> 
>     locking/mutex: Remove the list_head from struct mutex
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> 
> We could not revert the patch because of merge conflict but resetting to the
> parent of the commit seems to fix the issue.
> 
> Could you please check why the patch causes this regression and provide a
> fix if necessary?

Does this help?

---
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -40,10 +40,10 @@ __ww_waiter_last(struct mutex *lock)
 	__must_hold(&lock->wait_lock)
 {
 	struct mutex_waiter *w = lock->first_waiter;
+	if (!w)
+		return NULL;
 
-	if (w)
-		w = list_prev_entry(w, list);
-	return w;
+	return __ww_waiter_prev(lock, w);
 }
 
 static inline void

Re: Regression on linux-next (next-20260324 )

[Peter Zijlstra]

On Fri, Mar 27, 2026 at 05:31:00PM +0100, Peter Zijlstra wrote:
> On Fri, Mar 27, 2026 at 07:09:26PM +0530, Borah, Chaitanya Kumar wrote:
> > Hello Matthew,
> > 
> > Hope you are doing well. I am Chaitanya from the linux graphics team in
> > Intel.
> > 
> > This mail is regarding a regression we are seeing in our CI runs[1] on
> > linux-next repository.
> > 
> > Since the version next-20260324 [2], we are seeing the following regression
> > 
> > `````````````````````````````````````````````````````````````````````````````````
> > <5>[  157.361977] [IGT] Inactivity timeout exceeded. Killing the current
> > test with SIGQUIT.
> > <6>[  157.362097] sysrq: HELP : loglevel(0-9) reboot(b) crash(c)
> > show-all-locks(d) terminate-all-tasks(e) memory-full-oom-kill(f)
> > kill-all-tasks(i) thaw-filesystems(j) sak(k)
> > show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n)
> > poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s)
> > show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w)
> > dump-ftrace-buffer(z) replay-kernel-logs(R)
> > <6>[  157.399543] sysrq: Show State
> > <6>[  157.403061] task:systemd         state:S stack:0     pid:1 tgid:1
> > ppid:0      task_flags:0x400100 flags:0x00080000
> > <6>[  157.403067] Call Trace:
> > <6>[  157.403069]  <TASK>
> > <6>[  157.403072]  __schedule+0x5d7/0x1ef0
> > <6>[  157.403078]  ? lock_acquire+0xc4/0x300
> > <6>[  157.403084]  ? schedule+0x10e/0x180
> > <6>[  157.403087]  ? lock_release+0xcd/0x2b0
> > <6>[  157.403092]  schedule+0x3a/0x180
> > <6>[  157.403094]  schedule_hrtimeout_range_clock+0x112/0x120
> > <6>[  157.403097]  ? do_epoll_wait+0x3e4/0x5b0
> > <6>[  157.403102]  ? lock_release+0xcd/0x2b0
> > <6>[  157.403104]  ? _raw_spin_unlock_irq+0x27/0x70
> > <6>[  157.403106]  ? do_epoll_wait+0x3e4/0x5b0
> > <6>[  157.403110]  schedule_hrtimeout_range+0x13/0x30
> > `````````````````````````````````````````````````````````````````````````````````
> > Details log can be found in [3].
> > 
> > After bisecting the tree, the following patch [4] seems to be the first
> > "bad" commit
> > 
> > `````````````````````````````````````````````````````````````````````````````````````````````````````````
> > commit 25500ba7e77ce9d3d9b5a1929d41a2ee2e23f6fe
> > Author: Matthew Wilcox (Oracle) willy@infradead.org
> > Date:   Thu Mar 5 19:55:43 2026 +0000
> > 
> >     locking/mutex: Remove the list_head from struct mutex
> > `````````````````````````````````````````````````````````````````````````````````````````````````````````
> > 
> > We could not revert the patch because of merge conflict but resetting to the
> > parent of the commit seems to fix the issue.
> > 
> > Could you please check why the patch causes this regression and provide a
> > fix if necessary?
> 
> Does this help?

More tidy version of the same...

---
diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
index b1834ab7e782..bb8b410779d4 100644
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -42,7 +42,7 @@ __ww_waiter_last(struct mutex *lock)
 	struct mutex_waiter *w = lock->first_waiter;
 
 	if (w)
-		w = list_prev_entry(w, list);
+		w = __ww_waiter_prev(lock, w);
 	return w;
 }
 

Re: Regression on linux-next (next-20260324 )

[Borah, Chaitanya Kumar]

On 3/27/2026 10:13 PM, Peter Zijlstra wrote:
> On Fri, Mar 27, 2026 at 05:31:00PM +0100, Peter Zijlstra wrote:
>> On Fri, Mar 27, 2026 at 07:09:26PM +0530, Borah, Chaitanya Kumar wrote:
>>> Hello Matthew,
>>>
>>> Hope you are doing well. I am Chaitanya from the linux graphics team in
>>> Intel.
>>>
>>> This mail is regarding a regression we are seeing in our CI runs[1] on
>>> linux-next repository.
>>>
>>> Since the version next-20260324 [2], we are seeing the following regression
>>>
>>> `````````````````````````````````````````````````````````````````````````````````
>>> <5>[  157.361977] [IGT] Inactivity timeout exceeded. Killing the current
>>> test with SIGQUIT.
>>> <6>[  157.362097] sysrq: HELP : loglevel(0-9) reboot(b) crash(c)
>>> show-all-locks(d) terminate-all-tasks(e) memory-full-oom-kill(f)
>>> kill-all-tasks(i) thaw-filesystems(j) sak(k)
>>> show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n)
>>> poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s)
>>> show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w)
>>> dump-ftrace-buffer(z) replay-kernel-logs(R)
>>> <6>[  157.399543] sysrq: Show State
>>> <6>[  157.403061] task:systemd         state:S stack:0     pid:1 tgid:1
>>> ppid:0      task_flags:0x400100 flags:0x00080000
>>> <6>[  157.403067] Call Trace:
>>> <6>[  157.403069]  <TASK>
>>> <6>[  157.403072]  __schedule+0x5d7/0x1ef0
>>> <6>[  157.403078]  ? lock_acquire+0xc4/0x300
>>> <6>[  157.403084]  ? schedule+0x10e/0x180
>>> <6>[  157.403087]  ? lock_release+0xcd/0x2b0
>>> <6>[  157.403092]  schedule+0x3a/0x180
>>> <6>[  157.403094]  schedule_hrtimeout_range_clock+0x112/0x120
>>> <6>[  157.403097]  ? do_epoll_wait+0x3e4/0x5b0
>>> <6>[  157.403102]  ? lock_release+0xcd/0x2b0
>>> <6>[  157.403104]  ? _raw_spin_unlock_irq+0x27/0x70
>>> <6>[  157.403106]  ? do_epoll_wait+0x3e4/0x5b0
>>> <6>[  157.403110]  schedule_hrtimeout_range+0x13/0x30
>>> `````````````````````````````````````````````````````````````````````````````````
>>> Details log can be found in [3].
>>>
>>> After bisecting the tree, the following patch [4] seems to be the first
>>> "bad" commit
>>>
>>> `````````````````````````````````````````````````````````````````````````````````````````````````````````
>>> commit 25500ba7e77ce9d3d9b5a1929d41a2ee2e23f6fe
>>> Author: Matthew Wilcox (Oracle) willy@infradead.org
>>> Date:   Thu Mar 5 19:55:43 2026 +0000
>>>
>>>      locking/mutex: Remove the list_head from struct mutex
>>> `````````````````````````````````````````````````````````````````````````````````````````````````````````
>>>
>>> We could not revert the patch because of merge conflict but resetting to the
>>> parent of the commit seems to fix the issue.
>>>
>>> Could you please check why the patch causes this regression and provide a
>>> fix if necessary?
>>
>> Does this help?
> 
> More tidy version of the same...
> 
> ---
> diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
> index b1834ab7e782..bb8b410779d4 100644
> --- a/kernel/locking/ww_mutex.h
> +++ b/kernel/locking/ww_mutex.h
> @@ -42,7 +42,7 @@ __ww_waiter_last(struct mutex *lock)
>   	struct mutex_waiter *w = lock->first_waiter;
>   
>   	if (w)
> -		w = list_prev_entry(w, list);
> +		w = __ww_waiter_prev(lock, w);
>   	return w;
>   }
>   
Thank you for the response, Peter. Unfortunately, the issue is still 
seen with this change.

Regards
Chaitanya

Re: Regression on linux-next (next-20260324 )

[Peter Zijlstra]

On Mon, Mar 30, 2026 at 01:56:33PM +0530, Borah, Chaitanya Kumar wrote:
> > diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
> > index b1834ab7e782..bb8b410779d4 100644
> > --- a/kernel/locking/ww_mutex.h
> > +++ b/kernel/locking/ww_mutex.h
> > @@ -42,7 +42,7 @@ __ww_waiter_last(struct mutex *lock)
> >   	struct mutex_waiter *w = lock->first_waiter;
> >   	if (w)
> > -		w = list_prev_entry(w, list);
> > +		w = __ww_waiter_prev(lock, w);
> >   	return w;
> >   }
> Thank you for the response, Peter. Unfortunately, the issue is still seen
> with this change.

Bah, indeed. Looking at this after the weekend I see that it's actually
wrong.

But I haven't yet had a new idea. I don't suppose there is a relatively
easy way to reproduce this issue outside of your CI robot?

My current working thesis is that since this is graphics, this is
ww_mutex related. I'll go over this code once more...

✗ LGCI.VerificationFailed: failure for Regression on linux-next (next-20260324 )

[Patchwork]

== Series Details ==

Series: Regression on linux-next (next-20260324 )
URL   : https://patchwork.freedesktop.org/series/164008/
State : failure

== Summary ==

Address 'peterz@infradead.org' is not on the allowlist, which prevents CI from being triggered for this patch.
If you want Intel GFX CI to accept this address, please contact the script maintainers at i915-ci-infra@lists.freedesktop.org.
Exception occurred during validation, bailing out!

✗ LGCI.VerificationFailed: failure for Regression on linux-next (next-20260324 ) (rev2)

[Patchwork]

== Series Details ==

Series: Regression on linux-next (next-20260324 ) (rev2)
URL   : https://patchwork.freedesktop.org/series/164008/
State : failure

== Summary ==

Address 'peterz@infradead.org' is not on the allowlist, which prevents CI from being triggered for this patch.
If you want Intel GFX CI to accept this address, please contact the script maintainers at i915-ci-infra@lists.freedesktop.org.
Exception occurred during validation, bailing out!