* [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix
@ 2026-10-19 18:26 Konstantin Khorenko
2026-10-19 18:26 ` [Devel] [PATCH hci-8.1 1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test Konstantin Khorenko
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Konstantin Khorenko @ 2026-10-19 18:26 UTC (permalink / raw)
To: devel, 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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^ permalink raw reply [flat|nested] 6+ messages in thread* [Devel] [PATCH hci-8.1 1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test
2026-10-19 18:26 [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix Konstantin Khorenko
@ 2026-10-19 18:26 ` Konstantin Khorenko
2026-10-19 18:29 ` no-reply
2026-10-19 18:26 ` [Devel] [PATCH hci-8.1 2/2] ms/kbuild: move GCOV flags to scripts/Makefile.gcov Konstantin Khorenko
2026-10-19 19:54 ` [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix Konstantin Khorenko
2 siblings, 1 reply; 6+ messages in thread
From: Konstantin Khorenko @ 2026-10-19 18:26 UTC (permalink / raw)
To: devel, 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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^ permalink raw reply [flat|nested] 6+ messages in thread* [Devel] [PATCH hci-8.1 2/2] ms/kbuild: move GCOV flags to scripts/Makefile.gcov
2026-10-19 18:26 [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix Konstantin Khorenko
2026-10-19 18:26 ` [Devel] [PATCH hci-8.1 1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test Konstantin Khorenko
@ 2026-10-19 18:26 ` Konstantin Khorenko
2026-10-19 18:30 ` no-reply
2026-10-19 19:54 ` [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix Konstantin Khorenko
2 siblings, 1 reply; 6+ messages in thread
From: Konstantin Khorenko @ 2026-10-19 18:26 UTC (permalink / raw)
To: devel, 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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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix
2026-10-19 18:26 [Devel] [PATCH hci-8.1 0/2] ms/kbuild: GCOV follow-ups to the prefer-atomic fix Konstantin Khorenko
2026-10-19 18:26 ` [Devel] [PATCH hci-8.1 1/2] ms/kbuild: use $(CFLAGS_GCOV) in the prefer-atomic try-run test Konstantin Khorenko
2026-10-19 18:26 ` [Devel] [PATCH hci-8.1 2/2] ms/kbuild: move GCOV flags to scripts/Makefile.gcov Konstantin Khorenko
@ 2026-10-19 19:54 ` Konstantin Khorenko
2 siblings, 0 replies; 6+ messages in thread
From: Konstantin Khorenko @ 2026-10-19 19:54 UTC (permalink / raw)
To: devel, 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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