x86/mce/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.

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20241025024602.24318-2-qiuxu.zhuo@intel.com

diff --git a/arch/x86/kernel/cpu/mce/dev-mcelog.c b/arch/x86/kernel/cpu/mce/dev-mcelog.c
index af44fd5dbd7c3938dfba382851d1d555ca810861..8d023239ce18e907a4757c47ee03c50323e1cd62 100644 (file)
--- 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;
        }