linux-kernel - [PATCH v3 01/10] x86/mce/dev-mcelog: Use xchg() to get and clear the flags

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Message-Id: <20241025024602.24318-2-qiuxu.zhuo@intel.com>
Date: Fri, 25 Oct 2024 10:45:53 +0800
From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
To: bp@...en8.de,
	tony.luck@...el.com
Cc: tglx@...utronix.de,
	dave.hansen@...ux.intel.com,
	mingo@...hat.com,
	hpa@...or.com,
	x86@...nel.org,
	linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	qiuxu.zhuo@...el.com
Subject: [PATCH v3 01/10] x86/mce/dev-mcelog: Use xchg() to get and clear the flags

Using xchg() to atomically get and clear the MCE log buffer flags,
streamlines the code and reduces the text size by 20 bytes.

  $ size dev-mcelog.o.*

       text	   data	    bss	    dec	    hex	filename
       3013	    360	    160	   3533	    dcd	dev-mcelog.o.old
       2993	    360	    160	   3513	    db9	dev-mcelog.o.new

No functional changes intended.

Reviewed-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>
Reviewed-by: Sohil Mehta <sohil.mehta@...el.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
---
Changes in v3:
  - Collect "Reviewed-by:" from Nikolay & Sohil.

Changes in v2:
  - Collect "Reviewed-by:" from Tony.

 arch/x86/kernel/cpu/mce/dev-mcelog.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/dev-mcelog.c b/arch/x86/kernel/cpu/mce/dev-mcelog.c
index af44fd5dbd7c..8d023239ce18 100644
--- a/arch/x86/kernel/cpu/mce/dev-mcelog.c
+++ b/arch/x86/kernel/cpu/mce/dev-mcelog.c
@@ -264,15 +264,8 @@ static long mce_chrdev_ioctl(struct file *f, unsigned int cmd,
 		return put_user(sizeof(struct mce), p);
 	case MCE_GET_LOG_LEN:
 		return put_user(mcelog->len, p);
-	case MCE_GETCLEAR_FLAGS: {
-		unsigned flags;
-
-		do {
-			flags = mcelog->flags;
-		} while (cmpxchg(&mcelog->flags, flags, 0) != flags);
-
-		return put_user(flags, p);
-	}
+	case MCE_GETCLEAR_FLAGS:
+		return put_user(xchg(&mcelog->flags, 0), p);
 	default:
 		return -ENOTTY;
 	}
-- 
2.17.1