linux-kernel - [rfc, PATCH v1 1/1] hrtimers: Refactor hrtimer_clock_to_base

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Message-ID: <20250210082907.4059064-1-andriy.shevchenko@linux.intel.com>
Date: Mon, 10 Feb 2025 10:26:02 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Cc: Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [rfc, PATCH v1 1/1] hrtimers: Refactor hrtimer_clock_to_base_table initialisation

Clang complains 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).

Refactor hrtimer_clock_to_base_table initialisation to make
the compiler happy.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---

TBH, I don't like much this solution as it diminishes the point of that
override to be there in the first place. I haven't found better alternatives
as they may be too intrusive. Another one might be to remove this table,
but in such case the replacement might add latency to some cases (although
I haven't checked the generated code for, for example, switch-case approach).
In any case this is an rfc, I would be glad if somebody fixes this in a better
way.

 kernel/time/hrtimer.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index deb1aa32814e..8ec6ff36b9ad 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -118,13 +118,21 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
 };
 
 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_PROCESS_CPUTIME_ID]		= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_THREAD_CPUTIME_ID]		= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_MONOTONIC_RAW]			= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_REALTIME_COARSE]			= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_MONOTONIC_COARSE]		= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_BOOTTIME]			= HRTIMER_BASE_BOOTTIME,
+	[CLOCK_REALTIME_ALARM]			= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_BOOTTIME_ALARM]			= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_SGI_CYCLE]			= HRTIMER_MAX_CLOCK_BASES,
+	[CLOCK_TAI]				= HRTIMER_BASE_TAI,
 
-	[CLOCK_REALTIME]	= HRTIMER_BASE_REALTIME,
-	[CLOCK_MONOTONIC]	= HRTIMER_BASE_MONOTONIC,
-	[CLOCK_BOOTTIME]	= HRTIMER_BASE_BOOTTIME,
-	[CLOCK_TAI]		= HRTIMER_BASE_TAI,
+	/* Make sure we catch unsupported clockids */
+	[CLOCK_TAI + 1 ... MAX_CLOCKS - 1]	= HRTIMER_MAX_CLOCK_BASES,
 };
 
 static inline bool hrtimer_base_is_online(struct hrtimer_cpu_base *base)
-- 
2.45.1.3035.g276e886db78b