mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-04-09 14:45:27 +00:00
Code Issues Packages Projects Releases Wiki Activity

um/locking: Remove semicolon from "lock" prefix

Browse Source 
Minimum version of binutils required to compile the kernel is 2.25.
This version correctly handles the "lock" prefix, so it is possible
to remove the semicolon, which was used to support ancient versions
of GNU as.

Due to the semicolon, the compiler considers "lock; insn" as two
separate instructions. Removing the semicolon makes asm length
calculations more accurate, consequently making scheduling and
inlining decisions of the compiler more accurate.

Removing the semicolon also enables assembler checks involving lock
prefix. Trying to assemble e.g. "lock andl %eax, %ebx" results in:

  Error: expecting lockable instruction after `lock'

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://patch.msgid.link/20250228090058.2499163-1-ubizjak@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Uros Bizjak 2025-02-28 10:00:08 +01:00 committed by Johannes Berg
parent e82cf3051e
commit 089db01ea7
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/um/asm/barrier.h
View File

@ -12,9 +12,9 @@
*/
#ifdef CONFIG_X86_32
#define mb() alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
#define rmb() alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
#define wmb() alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
#define mb() alternative("lock addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
#define rmb() alternative("lock addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
#define wmb() alternative("lock addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
#else /* CONFIG_X86_32 */