linux-kernel - [tip: timers/core] hrtimers: Replace hrtimer_clock_to_base

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Message-ID: <173987073439.10177.6616090097392460077.tip-bot2@tip-bot2>
Date: Tue, 18 Feb 2025 09:25:34 -0000
From: "tip-bot2 for Andy Shevchenko" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: timers/core] hrtimers: Replace hrtimer_clock_to_base_table with
 switch-case

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     4441b976dfeff0d3579e8da3c0283300c618a553
Gitweb:        https://git.kernel.org/tip/4441b976dfeff0d3579e8da3c0283300c618a553
Author:        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
AuthorDate:    Fri, 14 Feb 2025 15:43:33 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Tue, 18 Feb 2025 10:12:49 +01:00

hrtimers: Replace hrtimer_clock_to_base_table with switch-case

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
---
 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 deb1aa3..453dc76 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))
@@ -1587,14 +1577,19 @@ 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 enum hrtimer_restart hrtimer_dummy_timeout(struct hrtimer *unused)