[Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix

[Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix

[Konstantin Khorenko]

Two follow-ups to commit 6e1a837a05d4 ("ms/gcov: use atomic counter
updates to fix concurrent access crashes"). Peter Oberparleiter suggested
them while reviewing the upstream patch.

Both are taken from the akpm/mm tree, branch mm-nonmm-stable, and are not
in Linus's tree yet:

  4719c9264131 kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test
  f541906e89f9 kbuild: move GCOV flags to scripts/Makefile.gcov

- Patch 1 makes the try-run test compile with $(CFLAGS_GCOV) instead of a
  copy of its flags, so the test also sees -fno-tree-loop-im. The outcome
  of the test is unchanged.
- Patch 2 moves the CFLAGS_GCOV block into scripts/Makefile.gcov,
  included via include-$(CONFIG_GCOV_KERNEL) like the KCOV and KASAN
  makefiles. Builds without GCOV no longer run the try-run.

Patch 2 had a context conflict in Makefile: the CFLAGS_GCOV block has
different neighbours in this tree. The resolution is noted in the commit.

Upstream series:
https://lore.kernel.org/lkml/20261001-b4-prep-gcov-v1-0-794792e06f24@virtuozzo.com/

https://virtuozzo.atlassian.net/browse/VSTOR-148131

Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
Konstantin Khorenko (2):
      ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test
      ms/kbuild: move GCOV flags to scripts/Makefile.gcov

 MAINTAINERS           |  1 +
 Makefile              | 22 +---------------------
 scripts/Makefile.gcov | 21 +++++++++++++++++++++
 3 files changed, 23 insertions(+), 21 deletions(-)
---
base-commit: 8026fb5599f945a36a6911f8febad3ab569176da
change-id: 20261019-b4-prep-khorenko-vstor-148131-gcov-followups-697f640b297e

Best regards,
--  
Konstantin Khorenko <khorenko@virtuozzo.com>

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[Devel] [PATCH hci-8.1 1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test

[Konstantin Khorenko]

Patch series "kbuild: GCOV cleanups following the prefer-atomic fix".

Two cleanups Peter Oberparleiter suggested while reviewing commit
56cb9b7d96b2 ("gcov: use atomic counter updates to fix concurrent access
crashes"):

https://lore.kernel.org/e1b6e768-51af-468b-a729-0ed3fceef2f1@linux.ibm.com

Patch 1 makes the prefer-atomic try-run test reuse $(CFLAGS_GCOV) instead
of spelling the flags out again, so the test compiles with the exact GCOV
flags, -fno-tree-loop-im included.

Patch 2 moves the CFLAGS_GCOV block into scripts/Makefile.gcov, included
via include-$(CONFIG_GCOV_KERNEL) like the other instrumentation
makefiles.  The try-run also stops running on builds without GCOV.

This patch (of 2):

Reference $(CFLAGS_GCOV) in the try-run test introduced by
commit 56cb9b7d96b2 ("gcov: use atomic counter updates to fix
concurrent access crashes"), otherwise it can miss potential future
changes in the list of flags used for GCOV profiling like it misses
-fno-tree-loop-im at the moment.

The outcome of the test is unchanged: -fno-tree-loop-im does not affect
the undefined symbols the test compares.

Link: https://lore.kernel.org/20261001-b4-prep-gcov-v1-0-794792e06f24@virtuozzo.com
Link: https://lore.kernel.org/20261001-b4-prep-gcov-v1-1-794792e06f24@virtuozzo.com
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nsc@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mikhail Zaslonko <zaslonko@linux.ibm.com>
(cherry picked from commit 4719c9264131b88fef209dc3342c23d3ac5356bd)
Picked from the akpm/mm tree, branch mm-nonmm-stable: not in Linus's
tree yet.

https://virtuozzo.atlassian.net/browse/VSTOR-148131
Feature: fix ms/gcov
Assisted-by: LLM
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 Makefile | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index 288224078377f..3524889b5bb5f 100644
--- a/Makefile
+++ b/Makefile
@@ -1041,11 +1041,11 @@ CFLAGS_GCOV	+= -fno-tree-loop-im
 # undefined symbols (e.g. libatomic calls that the kernel cannot link).
 CFLAGS_GCOV	+= $(call try-run,\
 	echo 'long long x; void f(void){x++;}' | \
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w -fprofile-arcs \
-	-ftest-coverage -x c - -c -o "$$TMP.base" && \
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
+	-x c - -c -o "$$TMP.base" && \
 	echo 'long long x; void f(void){x++;}' | \
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w -fprofile-arcs \
-	-ftest-coverage -fprofile-update=prefer-atomic \
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
+	-fprofile-update=prefer-atomic \
 	-x c - -c -o "$$TMP" && \
 	$(NM) "$$TMP.base" | grep ' U ' > "$$TMP.ubase" || true ; \
 	$(NM) "$$TMP" | grep ' U ' > "$$TMP.utest" || true ; \

-- 
2.43.0

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[Devel] [PATCH hci-8.1 2/2] ms/kbuild: move GCOV flags to scripts/Makefile.gcov

[Konstantin Khorenko]

 * split the CFLAGS_GCOV block out of the top-level Makefile into
   scripts/Makefile.gcov
 * include it via include-$(CONFIG_GCOV_KERNEL) like neighbour
   KASAN/KCOV/UBSAN makefiles do
 * keep the include before scripts/Makefile.gcc-plugins: the try-run
   must not get -fplugin= options, plugins do not exist on clean builds

CFLAGS_GCOV is no longer defined when CONFIG_GCOV_KERNEL is off:
 * its user in scripts/Makefile.lib is guarded by the CONFIG_GCOV_KERNEL
 * in i915/xe header an empty value is harmless

The try-run compiler invocations also stop running on builds without
GCOV.

Link: https://lore.kernel.org/20261001-b4-prep-gcov-v1-2-794792e06f24@virtuozzo.com
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nsc@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mikhail Zaslonko <zaslonko@linux.ibm.com>
(cherry picked from commit f541906e89f9d08ef29f058b6cef1db071cd8163)
Picked from the akpm/mm tree, branch mm-nonmm-stable: not in Linus's
tree yet.

Conflict in Makefile: the CFLAGS_GCOV block sits next to different
lines in this tree. Removed the block and kept the local context.

https://virtuozzo.atlassian.net/browse/VSTOR-148131
Feature: fix ms/gcov
Assisted-by: LLM
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 MAINTAINERS           |  1 +
 Makefile              | 22 +---------------------
 scripts/Makefile.gcov | 21 +++++++++++++++++++++
 3 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 9523da3c767cb..f0f955907fd7d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9535,6 +9535,7 @@ M:	Peter Oberparleiter <oberpar@linux.ibm.com>
 S:	Maintained
 F:	Documentation/dev-tools/gcov.rst
 F:	kernel/gcov/
+F:	scripts/Makefile.gcov
 
 GDB KERNEL DEBUGGING HELPER SCRIPTS
 M:	Jan Kiszka <jan.kiszka@siemens.com>
diff --git a/Makefile b/Makefile
index 3524889b5bb5f..7c8f8e9b9be99 100644
--- a/Makefile
+++ b/Makefile
@@ -1033,27 +1033,6 @@ ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS   += -fconserve-stack
 endif
 
-CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage
-ifdef CONFIG_CC_IS_GCC
-CFLAGS_GCOV	+= -fno-tree-loop-im
-# Use atomic counter updates to avoid concurrent-access crashes in GCOV.
-# Only enable if -fprofile-update=prefer-atomic does not introduce new
-# undefined symbols (e.g. libatomic calls that the kernel cannot link).
-CFLAGS_GCOV	+= $(call try-run,\
-	echo 'long long x; void f(void){x++;}' | \
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
-	-x c - -c -o "$$TMP.base" && \
-	echo 'long long x; void f(void){x++;}' | \
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
-	-fprofile-update=prefer-atomic \
-	-x c - -c -o "$$TMP" && \
-	$(NM) "$$TMP.base" | grep ' U ' > "$$TMP.ubase" || true ; \
-	$(NM) "$$TMP" | grep ' U ' > "$$TMP.utest" || true ; \
-	cmp -s "$$TMP.ubase" "$$TMP.utest",\
-	-fprofile-update=prefer-atomic)
-endif
-export CFLAGS_GCOV
-
 # change __FILE__ to the relative path from the srctree
 KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
 
@@ -1066,6 +1045,7 @@ include-$(CONFIG_KCSAN)		+= scripts/Makefile.kcsan
 include-$(CONFIG_KMSAN)		+= scripts/Makefile.kmsan
 include-$(CONFIG_UBSAN)		+= scripts/Makefile.ubsan
 include-$(CONFIG_KCOV)		+= scripts/Makefile.kcov
+include-$(CONFIG_GCOV_KERNEL)	+= scripts/Makefile.gcov
 include-$(CONFIG_RANDSTRUCT)	+= scripts/Makefile.randstruct
 include-$(CONFIG_AUTOFDO_CLANG)	+= scripts/Makefile.autofdo
 include-$(CONFIG_PROPELLER_CLANG)	+= scripts/Makefile.propeller
diff --git a/scripts/Makefile.gcov b/scripts/Makefile.gcov
new file mode 100644
index 0000000000000..16c5b876440c2
--- /dev/null
+++ b/scripts/Makefile.gcov
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage
+ifdef CONFIG_CC_IS_GCC
+CFLAGS_GCOV	+= -fno-tree-loop-im
+# Use atomic counter updates to avoid concurrent-access crashes in GCOV.
+# Only enable if -fprofile-update=prefer-atomic does not introduce new
+# undefined symbols (e.g. libatomic calls that the kernel cannot link).
+CFLAGS_GCOV	+= $(call try-run,\
+	echo 'long long x; void f(void){x++;}' | \
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
+	-x c - -c -o "$$TMP.base" && \
+	echo 'long long x; void f(void){x++;}' | \
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
+	-fprofile-update=prefer-atomic \
+	-x c - -c -o "$$TMP" && \
+	$(NM) "$$TMP.base" | grep ' U ' > "$$TMP.ubase" || true ; \
+	$(NM) "$$TMP" | grep ' U ' > "$$TMP.utest" || true ; \
+	cmp -s "$$TMP.ubase" "$$TMP.utest",\
+	-fprofile-update=prefer-atomic)
+endif
+export CFLAGS_GCOV

-- 
2.43.0

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Re: [Devel] [PATCH hci-8.1 1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test

[no-reply]

> Patch series "kbuild: GCOV cleanups following the prefer-atomic fix".
> 
> Two cleanups Peter Oberparleiter suggested while reviewing commit
> 56cb9b7d96b2 ("gcov: use atomic counter updates to fix concurrent access
> crashes"):
> 
> https://lore.kernel.org/e1b6e768-51af-468b-a729-0ed3fceef2f1@linux.ibm.com
> 
> Patch 1 makes the prefer-atomic try-run test reuse $(CFLAGS_GCOV) instead
> of spelling the flags out again, so the test compiles with the exact GCOV
> flags, -fno-tree-loop-im included.
> 
> Patch 2 moves the CFLAGS_GCOV block into scripts/Makefile.gcov, included
> via include-$(CONFIG_GCOV_KERNEL) like the other instrumentation
> makefiles.  The try-run also stops running on builds without GCOV.
> [ ... ]
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-148131
> Feature: fix ms/gcov
> Assisted-by: LLM
> Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261019-b4-prep-khorenko-vstor-148131-gcov-followups-v1-0-2932ec685608@virtuozzo.com?part=1


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Re: [Devel] [PATCH hci-8.1 2/2] ms/kbuild: move GCOV flags to scripts/Makefile.gcov

[no-reply]

>  * split the CFLAGS_GCOV block out of the top-level Makefile into
>    scripts/Makefile.gcov
>  * include it via include-$(CONFIG_GCOV_KERNEL) like neighbour
>    KASAN/KCOV/UBSAN makefiles do
>  * keep the include before scripts/Makefile.gcc-plugins: the try-run
>    must not get -fplugin= options, plugins do not exist on clean builds
> 
> CFLAGS_GCOV is no longer defined when CONFIG_GCOV_KERNEL is off:
>  * its user in scripts/Makefile.lib is guarded by the CONFIG_GCOV_KERNEL
>  * in i915/xe header an empty value is harmless
> 
> The try-run compiler invocations also stop running on builds without
> GCOV.
> 
> Link: https://lore.kernel.org/20261001-b4-prep-gcov-v1-2-794792e06f24@virtuozzo.com
> [ ... ]
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-148131
> Feature: fix ms/gcov
> Assisted-by: LLM
> Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261019-b4-prep-khorenko-vstor-148131-gcov-followups-v1-0-2932ec685608@virtuozzo.com?part=2


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Re: [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix

[Konstantin Khorenko]

On Mon, 19 Oct 2026 20:26:49 +0200, Konstantin Khorenko wrote:
> ms/kbuild: GCOV follow-ups to the prefer-atomic fix
> 
> Two follow-ups to commit 6e1a837a05d4 ("ms/gcov: use atomic counter
> updates to fix concurrent access crashes"). Peter Oberparleiter suggested
> them while reviewing the upstream patch.
> 
> Both are taken from the akpm/mm tree, branch mm-nonmm-stable, and are not
> in Linus's tree yet:
> 
> [...]

Applied to branch-rh10-6.12.0-211.52.1.22.x.vz10-ovz, will be released in rh10-6.12.0-211.52.1.22.9.vz10, thanks!

[1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/bcaa25137dc6
[2/2] ms/kbuild: move GCOV flags to scripts/Makefile.gcov
      https://bitbucket.org/virtuozzocore/vzkernel.vzs/commits/8f2170c160be

-- 
Konstantin Khorenko <khorenko@virtuozzo.com>

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