ARC: Add support for irqflags tracing and lockdep

Lockdep required a small fix to stacktrace API which was incorrectly
unwindign out of __switch_to for the current call frame.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

@@ -35,6 +35,12 @@ config ARC
 	select PERF_USE_VMALLOC
 	select HAVE_DEBUG_STACKOVERFLOW
 
+config TRACE_IRQFLAGS_SUPPORT
+	def_bool y
+
+config LOCKDEP_SUPPORT
+	def_bool y
+
 config SCHED_OMIT_FRAME_POINTER
 	def_bool y
 

arch/arc/include/asm/irqflags.h

@@ -151,16 +151,38 @@ static inline void arch_unmask_irq(unsigned int irq)
 
 #else
 
+#ifdef CONFIG_TRACE_IRQFLAGS
+
+.macro TRACE_ASM_IRQ_DISABLE
+	bl	trace_hardirqs_off
+.endm
+
+.macro TRACE_ASM_IRQ_ENABLE
+	bl	trace_hardirqs_on
+.endm
+
+#else
+
+.macro TRACE_ASM_IRQ_DISABLE
+.endm
+
+.macro TRACE_ASM_IRQ_ENABLE
+.endm
+
+#endif
+
 .macro IRQ_DISABLE  scratch
 	lr	\scratch, [status32]
 	bic	\scratch, \scratch, (STATUS_E1_MASK | STATUS_E2_MASK)
 	flag	\scratch
+	TRACE_ASM_IRQ_DISABLE
 .endm
 
 .macro IRQ_ENABLE  scratch
 	lr	\scratch, [status32]
 	or	\scratch, \scratch, (STATUS_E1_MASK | STATUS_E2_MASK)
 	flag	\scratch
+	TRACE_ASM_IRQ_ENABLE
 .endm
 
 #endif	/* __ASSEMBLY__ */

arch/arc/kernel/entry.S

@@ -250,6 +250,14 @@ ARC_ENTRY handle_interrupt_level1
 	lr  r0, [icause1]
 	and r0, r0, 0x1f
 
+#ifdef CONFIG_TRACE_IRQFLAGS
+	; icause1 needs to be read early, before calling tracing, which
+	; can clobber scratch regs, hence use of stack to stash it
+	push r0
+	TRACE_ASM_IRQ_DISABLE
+	pop  r0
+#endif
+
 	bl.d  @arch_do_IRQ
 	mov r1, sp
 
@@ -570,6 +578,7 @@ resume_user_mode_begin:
 	; --- (Slow Path #2) pending signal  ---
 	mov r0, sp	; pt_regs for arg to do_signal()/do_notify_resume()
 
+	GET_CURR_THR_INFO_FLAGS   r9
 	bbit0  r9, TIF_SIGPENDING, .Lchk_notify_resume
 
 	; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
@@ -635,6 +644,8 @@ resume_kernel_mode:
 
 restore_regs :
 
+	TRACE_ASM_IRQ_ENABLE
+
 	lr	r10, [status32]
 
 	; Restore REG File. In case multiple Events outstanding,

arch/arc/kernel/stacktrace.c

@@ -237,11 +237,13 @@ unsigned int get_wchan(struct task_struct *tsk)
  */
 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
+	/* Assumes @tsk is sleeping so unwinds from __switch_to */
 	arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
 }
 
 void save_stack_trace(struct stack_trace *trace)
 {
-	arc_unwind_core(current, NULL, __collect_all, trace);
+	/* Pass NULL for task so it unwinds the current call frame */
+	arc_unwind_core(NULL, NULL, __collect_all, trace);
 }
 #endif