[BUG] Linux-next fails to link on ARM in allmodconfig and allyesconfig

[BUG] Linux-next fails to link on ARM in allmodconfig and allyesconfig

[Maxim Kuvyrkov]

Hi Mohit,

It seems that your commit 3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf causes a link failure for ARM in allmodconfig and allyesconfig.  This happens for at least gcc-8 compiler.
===
ERROR: "__aeabi_uldivmod" [net/sched/sch_pie.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2
===

Would you please investigate?  Below are diagnostics from Linaro's automated bisection job.

===
Culprit:
<cut>
commit 3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf
Author: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Date:   Tue Feb 26 00:39:59 2019 +0530

   net: sched: pie: add more cases to auto-tune alpha and beta

   The current implementation scales the local alpha and beta
   variables in the calculate_probability function by the same
   amount for all values of drop probability below 1%.

   RFC 8033 suggests using additional cases for auto-tuning
   alpha and beta when the drop probability is less than 1%.

   In order to add more auto-tuning cases, MAX_PROB must be
   scaled by u64 instead of u32 to prevent underflow when
   scaling the local alpha and beta variables in the
   calculate_probability function.

   Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
   Signed-off-by: Dhaval Khandla <dhavaljkhandla26@gmail.com>
   Signed-off-by: Hrishikesh Hiraskar <hrishihiraskar@gmail.com>
   Signed-off-by: Manish Kumar B <bmanish15597@gmail.com>
   Signed-off-by: Sachin D. Patil <sdp.sachin@gmail.com>
   Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
   Acked-by: Dave Taht <dave.taht@gmail.com>
   Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
   Signed-off-by: David S. Miller <davem@davemloft.net>
</cut>

Results regressed from (for last_good == 30a92ad703b93a96588e05b5bcd7247d7350c673)
reset_artifacts:
-10
build_abe binutils:
-9
build_abe stage1:
-8
linux_n_obj:
26184
linux build successful:
all

to (for first_bad == 3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf)
reset_artifacts:
-10
build_abe binutils:
-9
build_abe stage1:
-8
linux_n_obj:
19184

First few errors in logs of first_bad:
ERROR: "__aeabi_uldivmod" [net/sched/sch_pie.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

Artifacts of last_good build: https://ci.linaro.org/job/tcwg_kernel-bisect-gnu-release-arm-next-allmodconfig/18/artifact/artifacts/build-30a92ad703b93a96588e05b5bcd7247d7350c673/
Artifacts of first_bad build: https://ci.linaro.org/job/tcwg_kernel-bisect-gnu-release-arm-next-allmodconfig/18/artifact/artifacts/build-3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf/
===

--
Maxim Kuvyrkov
www.linaro.org




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Re: [BUG] Linux-next fails to link on ARM in allmodconfig and allyesconfig

[Leslie Monis]

On Thu, Feb 28, 2019 at 10:29:42AM +0300, Maxim Kuvyrkov wrote:
> Hi Mohit,
> 
> It seems that your commit 3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf causes a link failure for ARM in allmodconfig and allyesconfig.  This happens for at least gcc-8 compiler.
> ===
> ERROR: "__aeabi_uldivmod" [net/sched/sch_pie.ko] undefined!
> make[1]: *** [__modpost] Error 1
> make: *** [modules] Error 2
> ===
> 
> Would you please investigate?  Below are diagnostics from Linaro's automated bisection job.
> 
> ===
> Culprit:
> <cut>
> commit 3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf
> Author: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
> Date:   Tue Feb 26 00:39:59 2019 +0530
> 
>    net: sched: pie: add more cases to auto-tune alpha and beta
> 
>    The current implementation scales the local alpha and beta
>    variables in the calculate_probability function by the same
>    amount for all values of drop probability below 1%.
> 
>    RFC 8033 suggests using additional cases for auto-tuning
>    alpha and beta when the drop probability is less than 1%.
> 
>    In order to add more auto-tuning cases, MAX_PROB must be
>    scaled by u64 instead of u32 to prevent underflow when
>    scaling the local alpha and beta variables in the
>    calculate_probability function.
> 
>    Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
>    Signed-off-by: Dhaval Khandla <dhavaljkhandla26@gmail.com>
>    Signed-off-by: Hrishikesh Hiraskar <hrishihiraskar@gmail.com>
>    Signed-off-by: Manish Kumar B <bmanish15597@gmail.com>
>    Signed-off-by: Sachin D. Patil <sdp.sachin@gmail.com>
>    Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
>    Acked-by: Dave Taht <dave.taht@gmail.com>
>    Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
>    Signed-off-by: David S. Miller <davem@davemloft.net>
> </cut>
> 
> Results regressed from (for last_good == 30a92ad703b93a96588e05b5bcd7247d7350c673)
> reset_artifacts:
> -10
> build_abe binutils:
> -9
> build_abe stage1:
> -8
> linux_n_obj:
> 26184
> linux build successful:
> all
> 
> to (for first_bad == 3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf)
> reset_artifacts:
> -10
> build_abe binutils:
> -9
> build_abe stage1:
> -8
> linux_n_obj:
> 19184
> 
> First few errors in logs of first_bad:
> ERROR: "__aeabi_uldivmod" [net/sched/sch_pie.ko] undefined!
> make[1]: *** [__modpost] Error 1
> make: *** [modules] Error 2
> 
> Artifacts of last_good build: https://ci.linaro.org/job/tcwg_kernel-bisect-gnu-release-arm-next-allmodconfig/18/artifact/artifacts/build-30a92ad703b93a96588e05b5bcd7247d7350c673/
> Artifacts of first_bad build: https://ci.linaro.org/job/tcwg_kernel-bisect-gnu-release-arm-next-allmodconfig/18/artifact/artifacts/build-3f7ae5f3dc5295ac17d6521130ed8a8f8a723fbf/
> ===
> 
> --
> Maxim Kuvyrkov
> www.linaro.org
> 
> 
> 

Hi Max,

This bug was fixed by commit ff8285f81822dc8f528b36b6c5c8ab132367e92d

commit ff8285f81822dc8f528b36b6c5c8ab132367e92d
Author: Leslie Monis <lesliemonis@gmail.com>
Date:   Wed Feb 27 06:30:06 2019 +0530

    net: sched: pie: fix 64-bit division
    
    Use div_u64() to resolve build failures on 32-bit platforms.
    
    Fixes: 3f7ae5f3dc52 ("net: sched: pie: add more cases to auto-tune alpha and beta")
    Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
    Reported-by: Randy Dunlap <rdunlap@infradead.org>
    Tested-by: Randy Dunlap <rdunlap@infradead.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Leslie

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