linux-kernel - [PATCH v3 0/7] x86: Rewrite switch

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Date:	Sat, 13 Aug 2016 12:38:15 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH v3 0/7] x86: Rewrite switch_to()

This patch set simplifies the switch_to() code, by moving the stack switch
code out of line into an asm stub before calling __switch_to().  This ends
up being more readable, and using the C calling convention instead of
clobbering all registers improves code generation.  It also allows newly
forked processes to construct a special stack frame to seamlessly flow
to ret_from_fork, instead of using a test and branch, or an unbalanced
call/ret.

Changes from v2:
- Updated comments around kernel threads being uncommon for fork, etc.
- Removed STACK_FRAME_NON_STANDARD annotation from __schedule() per Josh Poimboeuf
- A few minor cleanups added

Changes from v1:
- Added struct inactive_task_frame
- Added comments about kernel threads returning to userspace
- Cleaned up some incorrect uses of thread.sp
- Rearranged inactive stack frame so that BP (frame pointer) is in the natural position right below the return address.  This should take care of unwinding issues Josh raised.

Brian Gerst (7):
  x86-32, kgdb: Don't use thread.ip in sleeping_thread_to_gdb_regs()
  x86-64, kgdb: clear GDB_PS on 64-bit
  x86: Add struct inactive_task_frame
  x86: Rewrite switch_to() code
  x86: Pass kernel thread parameters in fork_frame
  x86: Fix thread_saved_pc()
  Revert "sched: Mark __schedule() stack frame as non-standard"

 arch/x86/entry/entry_32.S          |  68 +++++++++++++-----
 arch/x86/entry/entry_64.S          |  78 ++++++++++++++------
 arch/x86/include/asm/processor.h   |  13 +---
 arch/x86/include/asm/stacktrace.h  |   4 +-
 arch/x86/include/asm/switch_to.h   | 144 ++++++++-----------------------------
 arch/x86/include/asm/thread_info.h |   2 -
 arch/x86/kernel/asm-offsets.c      |   6 ++
 arch/x86/kernel/asm-offsets_32.c   |   5 ++
 arch/x86/kernel/asm-offsets_64.c   |   5 ++
 arch/x86/kernel/kgdb.c             |   8 +--
 arch/x86/kernel/process.c          |  14 +++-
 arch/x86/kernel/process_32.c       |  31 +++-----
 arch/x86/kernel/process_64.c       |  21 +++---
 arch/x86/kernel/smpboot.c          |   1 -
 kernel/sched/core.c                |   1 -
 15 files changed, 190 insertions(+), 211 deletions(-)

-- 
2.5.5