tree 87cd8f6aee11c02d8d1681fadb88df1a60489cab
parent 90522d30b223fe35957fc8c8ee3b7a63dc9844b1
author Andy Lutomirski <luto@kernel.org> 1517164730 -0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1518030742 -0800

x86/asm: Move 'status' from thread_struct to thread_info

commit 37a8f7c38339b22b69876d6f5a0ab851565284e3

The TS_COMPAT bit is very hot and is accessed from code paths that mostly
also touch thread_info::flags.  Move it into struct thread_info to improve
cache locality.

The only reason it was in thread_struct is that there was a brief period
during which arch-specific fields were not allowed in struct thread_info.

Linus suggested further changing:

  ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

to:

  if (unlikely(ti->status & (TS_COMPAT|TS_I386_REGS_POKED)))
          ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

on the theory that frequently dirtying the cacheline even in pure 64-bit
code that never needs to modify status hurts performance.  That could be a
reasonable followup patch, but I suspect it matters less on top of this
patch.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>
Link: https://lkml.kernel.org/r/03148bcc1b217100e6e8ecf6a5468c45cf4304b6.1517164461.git.luto@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>