linux-kernel - [PATCH 02/11] ARM: VDSO: remove cntvct

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Message-Id: <20250826-vdso-cleanups-v1-2-d9b65750e49f@linutronix.de>
Date: Tue, 26 Aug 2025 08:17:05 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
 Vincenzo Frascino <vincenzo.frascino@....com>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>, Nam Cao <namcao@...utronix.de>, 
 Russell King <linux@...linux.org.uk>, Ingo Molnar <mingo@...hat.com>, 
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
 Madhavan Srinivasan <maddy@...ux.ibm.com>, 
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
 Christophe Leroy <christophe.leroy@...roup.eu>, 
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
 Alexander Gordeev <agordeev@...ux.ibm.com>, 
 Christian Borntraeger <borntraeger@...ux.ibm.com>, 
 Sven Schnelle <svens@...ux.ibm.com>, Arnd Bergmann <arnd@...db.de>, 
 Christian Brauner <brauner@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
 linux-arm-kernel@...ts.infradead.org, loongarch@...ts.linux.dev, 
 linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
 linux-s390@...r.kernel.org, linux-arch@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, 
 Rasmus Villemoes <linux@...musvillemoes.dk>, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH 02/11] ARM: VDSO: remove cntvct_ok global variable

From: Rasmus Villemoes <linux@...musvillemoes.dk>

The cntvct_ok variable has not had any external user since commit
c7a18100bdff ("lib/vdso: Avoid highres update if clocksource is not
VDSO capable").

It also only has one user in vdso.c, once during init, so rather than
having the caller of patch_vdso() initialize cntvct_ok, just call
cntvct_functional() directly and avoid the global variable entirely.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@....com>
---
 arch/arm/include/asm/vdso/vsyscall.h |  2 --
 arch/arm/kernel/vdso.c               | 10 +++-------
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/arm/include/asm/vdso/vsyscall.h b/arch/arm/include/asm/vdso/vsyscall.h
index 4e7226ad02ec4dcf88203c9046e1b320a10e7373..ff1c729af05f03ac5db86c28276db2e4a31c775c 100644
--- a/arch/arm/include/asm/vdso/vsyscall.h
+++ b/arch/arm/include/asm/vdso/vsyscall.h
@@ -7,8 +7,6 @@
 #include <vdso/datapage.h>
 #include <asm/cacheflush.h>

-extern bool cntvct_ok;
-
 static __always_inline
 void __arch_sync_vdso_time_data(struct vdso_time_data *vdata)
 {
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index 325448ffbba0c29895ea5d97e60d6f51e552cb2e..e38a30477f3d70939f6d57c79fad52eed73c49b4 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -54,11 +54,9 @@ struct elfinfo {
 	char		*dynstr;	/* ptr to .dynstr section */
 };

-/* Cached result of boot-time check for whether the arch timer exists,
- * and if so, whether the virtual counter is useable.
+/* Boot-time check for whether the arch timer exists, and if so,
+ * whether the virtual counter is usable.
  */
-bool cntvct_ok __ro_after_init;
-
 static bool __init cntvct_functional(void)
 {
 	struct device_node *np;
@@ -159,7 +157,7 @@ static void __init patch_vdso(void *ehdr)
 	 * want programs to incur the slight additional overhead of
 	 * dispatching through the VDSO only to fall back to syscalls.
 	 */
-	if (!cntvct_ok) {
+	if (!cntvct_functional()) {
 		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
 		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
 		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
@@ -197,8 +195,6 @@ static int __init vdso_init(void)
 	vdso_total_pages = VDSO_NR_PAGES; /* for the data/vvar pages */
 	vdso_total_pages += text_pages;

-	cntvct_ok = cntvct_functional();
-
 	patch_vdso(vdso_start);

 	return 0;

-- 
2.50.1