MN10300: Enable IRQs more in system call exit work path

Enable IRQs when calling schedule() for TIF_NEED_RESCHED and
do_notify_resume().  If interrupts are enabled during do_notify_resume(), a
warning can be seen (see lower down).

Whilst we're at it, resume_userspace can be made local to entry.S as it is not
called outside of there and it can be merged with the part of work_resched that
occurs after schedule() is called.

  WARNING: at kernel/softirq.c:160 local_bh_enable+0x42/0xa0()
  Call Trace:
    local_bh_enable+0x42/0xa0
    unix_release_sock+0x86/0x23c
    unix_release+0x20/0x28
    sock_release+0x17/0x88
    sock_close+0x20/0x28
    __fput+0xc9/0x1fc
    ____fput+0xb/0x10
    task_work_run+0x64/0x78
    do_notify_resume+0x53d/0x544
    work_notifysig+0xa/0xc

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ken Cox <jkc@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/mn10300/kernel/entry.S

@@ -108,10 +108,10 @@ syscall_exit_work:
 	and	EPSW_nSL,d0
 	beq	resume_kernel		# returning to supervisor mode
 
-	btst	_TIF_SYSCALL_TRACE,d2
-	beq	work_pending
 	LOCAL_IRQ_ENABLE		# could let syscall_trace_exit() call
 					# schedule() instead
+	btst	_TIF_SYSCALL_TRACE,d2
+	beq	work_pending
 	mov	fp,d0
 	call	syscall_trace_exit[],0	# do_syscall_trace(regs)
 	jmp	resume_userspace
@@ -124,6 +124,7 @@ work_pending:
 work_resched:
 	call	schedule[],0
 
+resume_userspace:
 	# make sure we don't miss an interrupt setting need_resched or
 	# sigpending between sampling and the rti
 	LOCAL_IRQ_DISABLE
@@ -132,6 +133,8 @@ work_resched:
 	mov	(TI_flags,a2),d2
 	btst	_TIF_WORK_MASK,d2
 	beq	restore_all
+
+	LOCAL_IRQ_ENABLE
 	btst	_TIF_NEED_RESCHED,d2
 	bne	work_resched
 
@@ -170,17 +173,6 @@ ret_from_intr:
 	and	EPSW_nSL,d0
 	beq	resume_kernel		# returning to supervisor mode
 
-ENTRY(resume_userspace)
-	# make sure we don't miss an interrupt setting need_resched or
-	# sigpending between sampling and the rti
-	LOCAL_IRQ_DISABLE
-
-	# is there any work to be done on int/exception return?
-	mov	(TI_flags,a2),d2
-	btst	_TIF_WORK_MASK,d2
-	bne	work_pending
-	jmp	restore_all
-
 #ifdef CONFIG_PREEMPT
 ENTRY(resume_kernel)
 	LOCAL_IRQ_DISABLE