sparc64: Reschedule KGDB capture to a software interrupt.

Otherwise it might interrupt switch_to() midstream and use
half-cooked register window state.

Reported-by: Chris Torek <chris.torek@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/pil.h

@@ -24,6 +24,7 @@
 #define PIL_DEVICE_IRQ		5
 #define PIL_SMP_CALL_FUNC_SNGL	6
 #define PIL_DEFERRED_PCR_WORK	7
+#define PIL_KGDB_CAPTURE	8
 #define PIL_NORMAL_MAX		14
 #define PIL_NMI			15
 

arch/sparc/kernel/kgdb_64.c

@@ -108,7 +108,7 @@ void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 }
 
 #ifdef CONFIG_SMP
-void smp_kgdb_capture_client(struct pt_regs *regs)
+void smp_kgdb_capture_client(int irq, struct pt_regs *regs)
 {
 	unsigned long flags;
 

arch/sparc/kernel/ttable.S

@@ -64,7 +64,12 @@ tl0_irq6:	TRAP_IRQ(smp_call_function_single_client, 6)
 tl0_irq6:	BTRAP(0x46)
 #endif
 tl0_irq7:	TRAP_IRQ(deferred_pcr_work_irq, 7)
-tl0_irq8:	BTRAP(0x48) BTRAP(0x49)
+#ifdef CONFIG_KGDB
+tl0_irq8:	TRAP_IRQ(smp_kgdb_capture_client, 8)
+#else
+tl0_irq8:	BTRAP(0x48)
+#endif
+tl0_irq9:	BTRAP(0x49)
 tl0_irq10:	BTRAP(0x4a) BTRAP(0x4b) BTRAP(0x4c) BTRAP(0x4d)
 tl0_irq14:	TRAP_IRQ(timer_interrupt, 14)
 tl0_irq15:	TRAP_NMI_IRQ(perfctr_irq, 15)

arch/sparc/mm/ultra.S

@@ -679,28 +679,8 @@ xcall_new_mmu_context_version:
 #ifdef CONFIG_KGDB
 	.globl		xcall_kgdb_capture
 xcall_kgdb_capture:
-661:	rdpr		%pstate, %g2
-	wrpr		%g2, PSTATE_IG | PSTATE_AG, %pstate
-	.section	.sun4v_2insn_patch, "ax"
-	.word		661b
-	nop
-	nop
-	.previous
-
-	rdpr		%pil, %g2
-	wrpr		%g0, PIL_NORMAL_MAX, %pil
-	sethi		%hi(109f), %g7
-	ba,pt		%xcc, etrap_irq
-109:	 or		%g7, %lo(109b), %g7
-#ifdef CONFIG_TRACE_IRQFLAGS
-	call		trace_hardirqs_off
-	 nop
-#endif
-	call		smp_kgdb_capture_client
-	 add		%sp, PTREGS_OFF, %o0
-	/* Has to be a non-v9 branch due to the large distance. */
-	ba		rtrap_xcall
-	 ldx		[%sp + PTREGS_OFF + PT_V9_TSTATE], %l1
+	wr		%g0, (1 << PIL_KGDB_CAPTURE), %set_softint
+	retry
 #endif
 
 #endif /* CONFIG_SMP */