Add context switch profile point.

Add the context switch profile point for x86 and ARM arquitectures.

Change-Id: Ib7205059104ed47b96ba75b8cfefec3ff35f6813
Signed-off-by: Yonattan Louise <yonattan.a.louise.mendoza@intel.com>

arch/arc/defconfig

@@ -16,6 +16,7 @@ CONFIG_XIP=y
 # CONFIG_EVENT_LOGGER is not set
 # CONFIG_KERNEL_PROFILER is not set
 # CONFIG_PROFILER_BUFFER_SIZE is not set
+# CONFIG_PROFILER_CONTEXT_SWITCH is not set
 
 #
 # Nanokernel Options

arch/arm/core/swap.S

@@ -73,6 +73,13 @@ SECTION_FUNC(TEXT, __pendsv)
 
     _GDB_STUB_EXC_ENTRY
 
+#ifdef CONFIG_PROFILER_CONTEXT_SWITCH
+	/* Register the context switch */
+	push {lr}
+	bl _sys_profiler_context_switch
+	pop {lr}
+#endif
+
     /* load _Nanokernel into r1 and current tCCS into r2 */
     ldr r1, =_nanokernel
     ldr r2, [r1, #__tNANO_current_OFFSET]

arch/arm/defconfig

@@ -17,6 +17,7 @@ CONFIG_XIP=y
 # CONFIG_EVENT_LOGGER is not set
 # CONFIG_KERNEL_PROFILER is not set
 # CONFIG_PROFILER_BUFFER_SIZE is not set
+# CONFIG_PROFILER_CONTEXT_SWITCH is not set
 
 #
 # Nanokernel Options

arch/x86/core/swap.S

@@ -136,6 +136,14 @@ SECTION_FUNC(TEXT, _Swap)
 	movl	__tNANO_current_OFFSET (%eax), %ecx
 	movl	%esp, __tCCS_coopReg_OFFSET + __tCoopReg_esp_OFFSET (%ecx)
 
+#ifdef CONFIG_PROFILER_CONTEXT_SWITCH
+	/* save %eax since it used as the return value for _Swap */
+	pushl	%eax
+	/* Register the context switch */
+	call	_sys_profiler_context_switch
+	/* restore _Swap's %eax */
+	popl	%eax
+#endif
 
 	/*
 	 * Determine what FIBER or TASK context needs to be swapped in. 

arch/x86/defconfig

@@ -19,6 +19,7 @@ CONFIG_ENHANCED_SECURITY=y
 # CONFIG_EVENT_LOGGER is not set
 # CONFIG_KERNEL_PROFILER is not set
 # CONFIG_PROFILER_BUFFER_SIZE is not set
+# CONFIG_PROFILER_CONTEXT_SWITCH is not set
 
 #
 # Security Options

include/misc/profiler.h

@@ -41,6 +41,10 @@
 
 #ifdef CONFIG_KERNEL_PROFILER
 
+#ifdef CONFIG_PROFILER_CONTEXT_SWITCH
+#define PROFILER_CONTEXT_SWITCH_EVENT_ID             0x0001
+#endif /* CONFIG_PROFILER_CONTEXT_SWITCH */
+
 /**
  * Global variable of the ring buffer that allows user to implement
  * their own reading routine.
@@ -142,6 +146,23 @@ void sys_profiler_put_timed(uint16_t event_id);
 	buffer_size, timeout)
 #endif /* CONFIG_NANO_TIMEOUTS */
 
+
+#ifdef CONFIG_PROFILER_CONTEXT_SWITCH
+
+/**
+ * @brief Register the fiber that calls the function as collector
+ *
+ * @details Initialize internal profiling data. This avoid registering the
+ * context switch of the collector fiber when CONFIG_PROFILE_CONTEXT_SWITCH
+ * is enable.
+ *
+ * @return No return value.
+ */
+void sys_profiler_register_as_collector(void);
+#else /* !CONFIG_PROFILER_CONTEXT_SWITCH */
+static inline void sys_profiler_register_as_collector(void) {};
+#endif /* CONFIG_PROFILER_CONTEXT_SWITCH */
+
 #else /* !CONFIG_KERNEL_PROFILER */
 
 static inline void sys_profiler_put(uint16_t event_id, uint32_t *event_data,

kernel/Kconfig

@@ -130,6 +130,18 @@ config PROFILER_BUFFER_SIZE
 	help
 	Buffer size in 32-bit words.
 
+menu "Profiler points"
+depends on KERNEL_PROFILER
+
+config PROFILER_CONTEXT_SWITCH
+	bool
+	prompt "Context switch profiler point"
+	default n
+	depends on KERNEL_PROFILER
+	help
+	Enable the context switch event messages.
+endmenu
+
 menu "Security Options"
 	depends on ENHANCED_SECURITY
 

kernel/nanokernel/profiler.c

@@ -37,9 +37,14 @@
 #include <misc/profiler.h>
 #include <misc/util.h>
 #include <init.h>
+#include <nano_private.h>
 
 uint32_t _sys_profiler_buffer[CONFIG_PROFILER_BUFFER_SIZE];
 
+#ifdef CONFIG_PROFILER_CONTEXT_SWITCH
+void *_collector_context=NULL;
+#endif
+
 /**
  * @brief Initialize the profiler system.
  *
@@ -69,3 +74,49 @@ void sys_profiler_put_timed(uint16_t event_id)
 	sys_event_logger_put(&sys_profiler_logger, event_id, data,
 		ARRAY_SIZE(data));
 }
+
+#ifdef CONFIG_PROFILER_CONTEXT_SWITCH
+void _sys_profiler_context_switch(void)
+{
+	extern tNANO _nanokernel;
+	uint32_t data[2];
+	extern void _sys_event_logger_put_non_preemptible(
+		struct event_logger *logger, uint16_t event_id, uint32_t *event_data,
+		uint8_t data_size);
+
+	/* if the profiler has not been initialized, we do nothing */
+	if (sys_profiler_logger.buffer == NULL) {
+		return;
+	}
+
+	if (_collector_context != _nanokernel.current) {
+		data[0] = nano_tick_get_32();
+		data[1] = (uint32_t)_nanokernel.current;
+
+		/*
+		 * The mechanism we use to log the profile events uses a sync semaphore
+		 * to inform that there are available events to be collected. The
+		 * context switch event can be triggered from a task context. When we
+		 * signal a semaphore from a task context and a fiber is waiting for
+		 * that semaphore, a context switch is generated immediately. Due to
+		 * the fact that we register the context switch event while the context
+		 * switch is being processed, a new context switch can be generated
+		 * before the kernel finishes processing the current context switch. We
+		 * need to prevent this because the kernel is not able to handle it.
+		 * The _sem_give_non_preemptible function does not trigger a context
+		 * switch when we signal the semaphore from any type of context. Using
+		 * _sys_event_logger_put_non_preemptible function, that internally uses
+		 * _sem_give_non_preemptible function for signaling the sync semaphore,
+		 * allow us registering the context switch event without triggering any
+		 * new context switch during the process.
+		 */
+		_sys_event_logger_put_non_preemptible(&sys_profiler_logger,
+			PROFILER_CONTEXT_SWITCH_EVENT_ID, data, ARRAY_SIZE(data));
+	}
+}
+
+void sys_profiler_register_as_collector(void)
+{
+	_collector_context = _nanokernel.current;
+}
+#endif /* CONFIG_PROFILER_CONTEXT_SWITCH */