[PATCH 2/3] x86: make 64 bit ret_from_fork a little more similar to 32 bit

Ian Campbell
2011-07-25T10:03:21Z

The 64 bit version resets EFLAGS before calling schedule_tail() and
therefore leaves EFLAGS.IF clear. 32 bit resets EFLAGS after calling
schedule_tail() and therefore leaves EFLAGS.IF set. I don't think
there is any practical difference between the two approaches since
interrupts are actually reenabled within schedule_tail
(schedule_tail->finish_task_switch->finish_lock_switch->raw_spin_unlock_irq->...->local_irq_enable)
so arbitrarily pick the 32 bit version and make 64 bit look like that.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: x86@kernel.org
---
arch/x86/kernel/entry_64.S | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index b50d142..9c28bd5 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -394,13 +394,14 @@ END(save_paranoid)
ENTRY(ret_from_fork)
DEFAULT_FRAME

- LOCK ; btr $TIF_FORK,TI_flags(%r8)

- pushq_cfi $0x0002
- popfq_cfi # reset kernel eflags
+ LOCK ; btr $TIF_FORK,TI_flags(%r8)

call schedule_tail # rdi: 'prev' task parameter

+ pushq_cfi $0x0202
+ popfq_cfi # reset kernel eflags
+
GET_THREAD_INFO(%rcx)

RESTORE_REST
--
1.7.2.5