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s390: system call path micro optimization

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Add a pointer to the system call table to the thread_info structure.
The TIF_31BIT bit is set or cleared by SET_PERSONALITY exactly once
for the lifetime of a process. With the pointer to the correct system
call table in thread_info the system call code in entry64.S path can
drop the check for TIF_31BIT which saves a couple of instructions.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2013-04-24 12:58:39 +02:00
parent dc7ee00d47
commit 616498813b
6 changed files with 24 additions and 13 deletions
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3
arch/s390/kernel/entry.S
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@@ -188,6 +188,7 @@ sysc_vtime:
mvc __PT_INT_CODE(4,%r11),__LC_SVC_ILC
sysc_do_svc:
oi __TI_flags+3(%r12),_TIF_SYSCALL
l %r10,__TI_sysc_table(%r12) # 31 bit system call table
lh %r8,__PT_INT_CODE+2(%r11)
sla %r8,2 # shift and test for svc0
jnz sysc_nr_ok
@@ -198,7 +199,6 @@ sysc_do_svc:
lr %r8,%r1
sla %r8,2
sysc_nr_ok:
l %r10,BASED(.Lsys_call_table) # 31 bit system call table
xc __SF_BACKCHAIN(4,%r15),__SF_BACKCHAIN(%r15)
st %r2,__PT_ORIG_GPR2(%r11)
st %r7,STACK_FRAME_OVERHEAD(%r15)
@@ -906,7 +906,6 @@ cleanup_idle_wait:
.Ltrace_enter: .long do_syscall_trace_enter
.Ltrace_exit: .long do_syscall_trace_exit
.Lschedule_tail: .long schedule_tail
.Lsys_call_table: .long sys_call_table
.Lsysc_per: .long sysc_per + 0x80000000
#ifdef CONFIG_TRACE_IRQFLAGS
.Lhardirqs_on: .long trace_hardirqs_on_caller