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

From: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
To: "Mohit P. Tahiliani" <tahiliani@nitk.edu.in>
Cc: Dhaval Khandla <dhavaljkhandla26@gmail.com>,
	Manish Kumar B <bmanish15597@gmail.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	"David S. Miller" <davem@davemloft.net>,
	Dave Taht <dave.taht@gmail.com>,
	Leslie Monis <lesliemonis@gmail.com>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	"Sachin D. Patil" <sdp.sachin@gmail.com>,
	broonie@kernel.org,
	Hrishikesh Hiraskar <hrishihiraskar@gmail.com>,
	Arnd Bergmann <arnd@linaro.org>,
	linux-arm-kernel@lists.infradead.org
Subject: [BUG] Linux-next fails to link on ARM in allmodconfig and allyesconfig
Date: Thu, 28 Feb 2019 10:29:42 +0300	[thread overview]
Message-ID: <0B49A364-A5EC-4E23-BA39-9946523A1BAA@linaro.org> (raw)

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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