preempt: ipipe: : add preemption-safe hard_preempt_{enable, disable}() ops

Some inner code of the interrupt pipeline may have to traverse regular
kernel code which manipulates the preemption count, expecting full
serialization including with out-of-band contexts.

The hard_preempt_*() variants are substituted to the original
preempt_{enable, disable}() calls in these cases.

include/linux/ipipe_base.h

@@ -100,6 +100,9 @@ static inline void __ipipe_sync_stage(void)
 int __ipipe_log_printk(const char *fmt, va_list args);
 void __ipipe_flush_printk(unsigned int irq, void *cookie);
 
+#define __ipipe_get_cpu(flags)	({ (flags) = hard_preempt_disable(); ipipe_processor_id(); })
+#define __ipipe_put_cpu(flags)	hard_preempt_enable(flags)
+
 #define __ipipe_serial_debug(__fmt, __args...)	raw_printk(__fmt, ##__args)
 
 #else /* !CONFIG_IPIPE */
@@ -115,6 +118,16 @@ static inline void __ipipe_init_proc(void) { }
 
 static inline void __ipipe_idle(void) { }
 
+#define hard_preempt_disable()		({ preempt_disable(); 0; })
+#define hard_preempt_enable(flags)	({ preempt_enable(); (void)(flags); })
+
+#define __ipipe_get_cpu(flags)		({ (void)(flags); get_cpu(); })
+#define __ipipe_put_cpu(flags)		\
+	do {				\
+		(void)(flags);		\
+		put_cpu();		\
+	} while (0)
+
 #define __ipipe_root_tick_p(regs)	1
 
 #define ipipe_handle_domain_irq(__domain, __hwirq, __regs)	\

include/linux/preempt.h

@@ -255,7 +255,28 @@ do { \
 
 #endif /* CONFIG_PREEMPT_COUNT */
 
-#ifdef MODULE
+#ifdef CONFIG_IPIPE
+#define hard_preempt_disable()				\
+	({						\
+		unsigned long __flags__;		\
+		__flags__ = hard_local_irq_save();	\
+		if (__ipipe_root_p)			\
+			preempt_disable();		\
+		__flags__;				\
+	})
+
+#define hard_preempt_enable(__flags__)					\
+	do {								\
+		if (__ipipe_root_p) {					\
+			preempt_enable_no_resched();			\
+			hard_local_irq_restore(__flags__);		\
+			if (!hard_irqs_disabled_flags(__flags__))	\
+				preempt_check_resched();		\
+		} else							\
+			hard_local_irq_restore(__flags__);		\
+	} while (0)
+
+#elif defined(MODULE)
 /*
  * Modules have no business playing preemption tricks.
  */
@@ -263,7 +284,7 @@ do { \
 #undef preempt_enable_no_resched
 #undef preempt_enable_no_resched_notrace
 #undef preempt_check_resched
-#endif
+#endif	/* !IPIPE && MODULE */
 
 #define preempt_set_need_resched() \
 do { \