[S390] cleanup sysc_work and io_work code

Cleanup the #ifdef mess at io_work in entry[64].S and streamline the
TIF work code of the system call and io exit path.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 28 insertions, 47 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 6af7045280a8..ffebfb64b913 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -301,31 +301,29 @@ sysc_restore_trace_psw:
 #endif
 
 #
-# recheck if there is more work to do
-#
-sysc_work_loop:
-        tm      __TI_flags+3(%r9),_TIF_WORK_SVC
-        bz      BASED(sysc_restore)     # there is no work to do
-#
-# One of the work bits is on. Find out which one.
+# There is work to do, but first we need to check if we return to userspace.
 #
 sysc_work:
         tm      SP_PSW+1(%r15),0x01     # returning to user ?
         bno     BASED(sysc_restore)
+
+#
+# One of the work bits is on. Find out which one.
+#
+sysc_work_loop:
         tm      __TI_flags+3(%r9),_TIF_MCCK_PENDING
         bo      BASED(sysc_mcck_pending)
         tm      __TI_flags+3(%r9),_TIF_NEED_RESCHED
         bo      BASED(sysc_reschedule)
         tm      __TI_flags+3(%r9),_TIF_SIGPENDING
-        bnz     BASED(sysc_sigpending)
+        bo      BASED(sysc_sigpending)
         tm      __TI_flags+3(%r9),_TIF_NOTIFY_RESUME
-        bnz     BASED(sysc_notify_resume)
+        bo      BASED(sysc_notify_resume)
         tm      __TI_flags+3(%r9),_TIF_RESTART_SVC
         bo      BASED(sysc_restart)
         tm      __TI_flags+3(%r9),_TIF_SINGLE_STEP
         bo      BASED(sysc_singlestep)
-        b       BASED(sysc_restore)
-sysc_work_done:
+        b       BASED(sysc_return)      # beware of critical section cleanup
 
 #
 # _TIF_NEED_RESCHED is set, call schedule
@@ -386,7 +384,7 @@ sysc_singlestep:
         mvi     SP_SVCNR+1(%r15),0xff
         la      %r2,SP_PTREGS(%r15)     # address of register-save area
         l       %r1,BASED(.Lhandle_per) # load adr. of per handler
-        la      %r14,BASED(sysc_return) # load adr. of system return
+        la      %r14,BASED(sysc_work_loop)      # load adr. of system return
         br      %r1                     # branch to do_single_step
 
 #
@@ -636,30 +634,36 @@ io_restore_trace_psw:
 #endif
 
 #
-# switch to kernel stack, then check the TIF bits
+# There is work todo, find out in which context we have been interrupted:
+# 1) if we return to user space we can do all _TIF_WORK_INT work
+# 2) if we return to kernel code and preemptive scheduling is enabled check
+#    the preemption counter and if it is zero call preempt_schedule_irq
+# Before any work can be done, a switch to the kernel stack is required.
 #
 io_work:
         tm      SP_PSW+1(%r15),0x01     # returning to user ?
-#ifndef CONFIG_PREEMPT
-        bno     BASED(io_restore)       # no-> skip resched & signal
-#else
-        bnz     BASED(io_work_user)     # no -> check for preemptive scheduling
+        bo      BASED(io_work_user)     # yes -> do resched & signal
+#ifdef CONFIG_PREEMPT
         # check for preemptive scheduling
         icm     %r0,15,__TI_precount(%r9)
         bnz     BASED(io_restore)       # preemption disabled
+        # switch to kernel stack
         l       %r1,SP_R15(%r15)
         s       %r1,BASED(.Lc_spsize)
         mvc     SP_PTREGS(__PT_SIZE,%r1),SP_PTREGS(%r15)
         xc      __SF_BACKCHAIN(4,%r1),__SF_BACKCHAIN(%r1) # clear back chain
         lr      %r15,%r1
 io_resume_loop:
-        tm      __TI_flags+3(%r9),_TIF_NEED_RESCHED
-        bno     BASED(io_restore)
         l       %r1,BASED(.Lpreempt_schedule_irq)
         la      %r14,BASED(io_resume_loop)
-        br      %r1                     # call schedule
+        tm      __TI_flags+3(%r9),_TIF_NEED_RESCHED
+        bor     %r1                     # call preempt_schedule_irq
 #endif
+        b       BASED(io_restore)
 
+#
+# Need to do work before returning to userspace, switch to kernel stack
+#
 io_work_user:
         l       %r1,__LC_KERNEL_STACK
         s       %r1,BASED(.Lc_spsize)
@@ -668,7 +672,7 @@ io_work_user:
         lr      %r15,%r1
 #
 # One of the work bits is on. Find out which one.
-# Checked are: _TIF_SIGPENDING, _TIF_NEED_RESCHED
+# Checked are: _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_NEED_RESCHED
 #               and _TIF_MCCK_PENDING
 #
 io_work_loop:
@@ -677,11 +681,10 @@ io_work_loop:
         tm      __TI_flags+3(%r9),_TIF_NEED_RESCHED
         bo      BASED(io_reschedule)
         tm      __TI_flags+3(%r9),_TIF_SIGPENDING
-        bnz     BASED(io_sigpending)
+        bo      BASED(io_sigpending)
         tm      __TI_flags+3(%r9),_TIF_NOTIFY_RESUME
-        bnz     BASED(io_notify_resume)
-        b       BASED(io_restore)
-io_work_done:
+        bo      BASED(io_notify_resume)
+        b       BASED(io_return)        # beware of critical section cleanup
 
 #
 # _TIF_MCCK_PENDING is set, call handler
@@ -701,8 +704,6 @@ io_reschedule:
         basr    %r14,%r1                # call scheduler
         stnsm   __SF_EMPTY(%r15),0xfc   # disable I/O and ext. interrupts
         TRACE_IRQS_OFF
-        tm      __TI_flags+3(%r9),_TIF_WORK_INT
-        bz      BASED(io_restore)       # there is no work to do
         b       BASED(io_work_loop)
 
 #
@@ -921,14 +922,10 @@ cleanup_table_sysc_return:
         .long   sysc_return + 0x80000000, sysc_leave + 0x80000000
 cleanup_table_sysc_leave:
         .long   sysc_leave + 0x80000000, sysc_done + 0x80000000
-cleanup_table_sysc_work_loop:
-        .long   sysc_work_loop + 0x80000000, sysc_work_done + 0x80000000
 cleanup_table_io_return:
         .long   io_return + 0x80000000, io_leave + 0x80000000
 cleanup_table_io_leave:
         .long   io_leave + 0x80000000, io_done + 0x80000000
-cleanup_table_io_work_loop:
-        .long   io_work_loop + 0x80000000, io_work_done + 0x80000000
 
 cleanup_critical:
         clc     4(4,%r12),BASED(cleanup_table_system_call)
@@ -946,11 +943,6 @@ cleanup_critical:
         clc     4(4,%r12),BASED(cleanup_table_sysc_leave+4)
         bl      BASED(cleanup_sysc_leave)
 0:
-        clc     4(4,%r12),BASED(cleanup_table_sysc_work_loop)
-        bl      BASED(0f)
-        clc     4(4,%r12),BASED(cleanup_table_sysc_work_loop+4)
-        bl      BASED(cleanup_sysc_return)
-0:
         clc     4(4,%r12),BASED(cleanup_table_io_return)
         bl      BASED(0f)
         clc     4(4,%r12),BASED(cleanup_table_io_return+4)
@@ -961,11 +953,6 @@ cleanup_critical:
         clc     4(4,%r12),BASED(cleanup_table_io_leave+4)
         bl      BASED(cleanup_io_leave)
 0:
-        clc     4(4,%r12),BASED(cleanup_table_io_work_loop)
-        bl      BASED(0f)
-        clc     4(4,%r12),BASED(cleanup_table_io_work_loop+4)
-        bl      BASED(cleanup_io_work_loop)
-0:
         br      %r14
 
 cleanup_system_call:
@@ -1043,12 +1030,6 @@ cleanup_io_return:
         la      %r12,__LC_RETURN_PSW
         br      %r14
 
-cleanup_io_work_loop:
-        mvc     __LC_RETURN_PSW(4),0(%r12)
-        mvc     __LC_RETURN_PSW+4(4),BASED(cleanup_table_io_work_loop)
-        la      %r12,__LC_RETURN_PSW
-        br      %r14
-
 cleanup_io_leave:
         clc     4(4,%r12),BASED(cleanup_io_leave_insn)
         be      BASED(2f)