[PATCH] sh: preempt fixes

From: Paul Mundt <lethal@linux-sh.org>

This fixes up a number of other outstanding preemption issues in the sh
backend (in addition to the ones already fixed in previous patches).

Patch from Kaz Kojima.

arch/sh/kernel/entry.S

-/* $Id: entry.S,v 1.33 2003/11/22 15:39:51 lethal Exp $
+/* $Id: entry.S,v 1.34 2004/01/13 05:52:11 kkojima Exp $
  *
  *  linux/arch/sh/entry.S
  *
@@ -351,18 +351,22 @@ ret_from_irq:
 	 GET_THREAD_INFO(r8)
 
 #ifdef CONFIG_PREEMPT
+	bra	resume_userspace
+	 nop
 ENTRY(resume_kernel)
 	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
 	tst	r0, r0
-	bf	restore_all
+	bf	noresched
 need_resched:
 	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
 	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
-	bt	restore_all
+	bt	noresched
 
-	stc	sr, r0			! interrupts disabled?
-	tst	#0xf0, r0
-	bf	restore_all
+	mov	#OFF_SR, r0
+	mov.l	@(r0,r15), r0		! get status register
+	and	#0xf0, r0		! interrupts off (exception path)?
+	cmp/eq	#0xf0, r0
+	bt	noresched
 
 	mov.l	1f, r0
 	mov.l	r0, @(TI_PRE_COUNT,r8)
@@ -375,7 +379,10 @@ need_resched:
 	mov.l	r0, @(TI_PRE_COUNT,r8)
 	CLI()
 
-	bra need_resched
+	bra	need_resched
+	 nop
+noresched:
+	bra	restore_all
 	 nop
 
 	.align 2
@@ -525,7 +532,7 @@ ENTRY(system_call)
 	! Is the trap argument >= 0x20? (TRA will be >= 0x80)
 	mov	#0x7f, r9
 	cmp/hi	r9, r8
-	bt/s	debug_trap
+	bt/s	0f
 	 mov	#OFF_TRA, r9
 	add	r15, r9
 	!
@@ -543,6 +550,10 @@ syscall_badsys:			! Bad syscall number
 	bra	resume_userspace
 	 mov.l	r0, @(OFF_R0,r15)	! Return value
 	!
+0:
+	bra	debug_trap
+	 nop
+	!
 good_system_call:		! Good syscall number
 	mov.l	@(TI_FLAGS,r8), r8
 	mov	#_TIF_SYSCALL_TRACE, r10
@@ -632,12 +643,8 @@ skip_restore:
 	!
 	! Calculate new SR value
 	mov	k3, k2			! original SR value
-	mov.l	8f, k1
-	stc	sr, k0
-	and	k1, k0			! Get current FD-bit
 	mov.l	9f, k1
 	and	k1, k2			! Mask orignal SR value
-	or	k0, k2			! Inherit current FD-bit
 	!
 	mov	k3, k0			! Calculate IMASK-bits
 	shlr2	k0
@@ -668,8 +675,7 @@ skip_restore:
 4:	.long	do_syscall_trace
 5:	.long	0x00001000	! DSP
 7:	.long	0x30000000
-8:	.long	0x00008000	! FD
-9:	.long	0xffff7f0f	! ~(IMASK+FD)
+9:
 __INV_IMASK:
 	.long	0xffffff0f	! ~(IMASK)
 
@@ -838,7 +844,7 @@ skip_save:
 
 	.align	2
 1:	.long	0x00001000	! DSP=1
-2:	.long	0x000000f0	! FD=0, IMASK=15
+2:	.long	0x000080f0	! FD=1, IMASK=15
 3:	.long	0xcfffffff	! RB=0, BL=0
 4:	.long	exception_handling_table
 

arch/sh/kernel/irq.c

-/* $Id: irq.c,v 1.19 2004/01/10 01:25:32 lethal Exp $
+/* $Id: irq.c,v 1.20 2004/01/13 05:52:11 kkojima Exp $
  *
  * linux/arch/sh/kernel/irq.c
  *
@@ -318,6 +318,16 @@ asmlinkage int do_IRQ(unsigned long r4, unsigned long r5,
 
 	irq_enter();
 
+#ifdef CONFIG_PREEMPT
+	/*
+	 * At this point we're now about to actually call handlers,
+	 * and interrupts might get reenabled during them... bump
+	 * preempt_count to prevent any preemption while the handler
+	 * called here is pending...
+	 */
+	preempt_disable();
+#endif
+
 	/* Get IRQ number */
 	asm volatile("stc	r2_bank, %0\n\t"
 		     "shlr2	%0\n\t"
@@ -393,6 +403,15 @@ asmlinkage int do_IRQ(unsigned long r4, unsigned long r5,
 
 	irq_exit();
 
+#ifdef CONFIG_PREEMPT
+	/*
+	 * We're done with the handlers, interrupts should be
+	 * currently disabled; decrement preempt_count now so
+	 * as we return preemption may be allowed...
+	 */
+	preempt_enable_no_resched();
+#endif
+
 	return 1;
 }