linux-kernel - [tip: sched/core] math64: Always inline u128 version of mul_u64_u64

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Message-ID: <168599257757.404.12337040567990260583.tip-bot2@tip-bot2>
Date:   Mon, 05 Jun 2023 19:16:17 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Michael Kelley <mikelley@...rosoft.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] math64: Always inline u128 version of mul_u64_u64_shr()

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

Commit-ID:     fc4a0db4149afcdae2527f0d8c376accca34adc9
Gitweb:        https://git.kernel.org/tip/fc4a0db4149afcdae2527f0d8c376accca34adc9
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 19 May 2023 12:21:05 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 05 Jun 2023 21:11:06 +02:00

math64: Always inline u128 version of mul_u64_u64_shr()

In order to prevent the following complaint from happening, always
inline the u128 variant of mul_u64_u64_shr() -- which is what x86_64
will use.

  vmlinux.o: warning: objtool: read_hv_sched_clock_tsc+0x5a: call to mul_u64_u64_shr.constprop.0() leaves .noinstr.text section

It should compile into something like:

  asm("mul	%[mul];"
      "shrd	%rdx, %rax, %cl"
      : "+&a" (a)
      : "c" shift, [mul] "r" (mul)
      : "d");

Which is silly not to inline, but it happens.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Michael Kelley <mikelley@...rosoft.com>  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.637420396@infradead.org
---
 include/linux/math64.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/math64.h b/include/linux/math64.h
index 8b9191a..bf74478 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -168,7 +168,7 @@ static __always_inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
 #endif /* mul_u64_u32_shr */
 
 #ifndef mul_u64_u64_shr
-static inline u64 mul_u64_u64_shr(u64 a, u64 mul, unsigned int shift)
+static __always_inline u64 mul_u64_u64_shr(u64 a, u64 mul, unsigned int shift)
 {
 	return (u64)(((unsigned __int128)a * mul) >> shift);
 }