linux-kernel - [PATCH AUTOSEL 6.12 318/486] hrtimers: Replace hrtimer_clock_to_base

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Message-Id: <20250505223922.2682012-318-sashal@kernel.org>
Date: Mon,  5 May 2025 18:36:34 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sasha Levin <sashal@...nel.org>,
	anna-maria@...utronix.de,
	frederic@...nel.org,
	nathan@...nel.org,
	llvm@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.12 318/486] hrtimers: Replace hrtimer_clock_to_base_table with switch-case

From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

[ Upstream commit 4441b976dfeff0d3579e8da3c0283300c618a553 ]

Clang and GCC complain about overlapped initialisers in the
hrtimer_clock_to_base_table definition. With `make W=1` and CONFIG_WERROR=y
(which is default nowadays) this breaks the build:

  CC      kernel/time/hrtimer.o
kernel/time/hrtimer.c:124:21: error: initializer overrides prior initialization of this subobject [-Werror,-Winitializer-overrides]
  124 |         [CLOCK_REALTIME]        = HRTIMER_BASE_REALTIME,

kernel/time/hrtimer.c:122:27: note: previous initialization is here
  122 |         [0 ... MAX_CLOCKS - 1]  = HRTIMER_MAX_CLOCK_BASES,

(and similar for CLOCK_MONOTONIC, CLOCK_BOOTTIME, and CLOCK_TAI).

hrtimer_clockid_to_base(), which uses the table, is only used in
__hrtimer_init(), which is not a hotpath.

Therefore replace the table lookup with a switch case in
hrtimer_clockid_to_base() to avoid this warning.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/all/20250214134424.3367619-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/time/hrtimer.c | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index db9c06bb23116..06fbc226341fd 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -117,16 +117,6 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
 	.csd = CSD_INIT(retrigger_next_event, NULL)
 };
 
-static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
-	/* Make sure we catch unsupported clockids */
-	[0 ... MAX_CLOCKS - 1]	= HRTIMER_MAX_CLOCK_BASES,
-
-	[CLOCK_REALTIME]	= HRTIMER_BASE_REALTIME,
-	[CLOCK_MONOTONIC]	= HRTIMER_BASE_MONOTONIC,
-	[CLOCK_BOOTTIME]	= HRTIMER_BASE_BOOTTIME,
-	[CLOCK_TAI]		= HRTIMER_BASE_TAI,
-};
-
 static inline bool hrtimer_base_is_online(struct hrtimer_cpu_base *base)
 {
 	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
@@ -1597,14 +1587,19 @@ u64 hrtimer_next_event_without(const struct hrtimer *exclude)
 
 static inline int hrtimer_clockid_to_base(clockid_t clock_id)
 {
-	if (likely(clock_id < MAX_CLOCKS)) {
-		int base = hrtimer_clock_to_base_table[clock_id];
-
-		if (likely(base != HRTIMER_MAX_CLOCK_BASES))
-			return base;
+	switch (clock_id) {
+	case CLOCK_REALTIME:
+		return HRTIMER_BASE_REALTIME;
+	case CLOCK_MONOTONIC:
+		return HRTIMER_BASE_MONOTONIC;
+	case CLOCK_BOOTTIME:
+		return HRTIMER_BASE_BOOTTIME;
+	case CLOCK_TAI:
+		return HRTIMER_BASE_TAI;
+	default:
+		WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
+		return HRTIMER_BASE_MONOTONIC;
 	}
-	WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
-	return HRTIMER_BASE_MONOTONIC;
 }
 
 static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
-- 
2.39.5