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kernel: Eliminate use of main() in microkernel

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Revises microkernel initialization code by incorporating the existing
_k_kernel_init() and main() routines into _main(). This optimizes kernel
initialization a bit, and allows application code to use main()
if desired -- for example, as the entry point to an application task.
The change also eliminates the need for sysgen to generate a routine
whose content is always the same.

This change preserves the existing order of operations done during
kernel initialization, and leaves further improvements for later.

Change-Id: Ie03d8a6f38f8a311f398667ed977fd8478719d70
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
This commit is contained in:
Allan Stephens 2015-09-29 13:41:42 -04:00 • committed by Anas Nashif
commit ddaebc15b3
4 changed files with 37 additions and 43 deletions
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36
kernel/nanokernel/nano_init.c
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@ -69,7 +69,7 @@ const char * const build_timestamp = BUILD_TIMESTAMP;
#ifdef CONFIG_BOOT_TIME_MEASUREMENT
uint64_t __noinit __start_tsc; /* timestamp when kernel starts */
uint64_t __noinit __main_tsc; /* timestamp when main() starts */
uint64_t __noinit __main_tsc; /* timestamp when main task starts */
uint64_t __noinit __idle_tsc; /* timestamp when CPU goes idle */
#endif
@ -98,13 +98,6 @@ char __noinit __stack main_task_stack[CONFIG_MAIN_STACK_SIZE];
char __noinit _interrupt_stack[CONFIG_ISR_STACK_SIZE];
#endif
/*
* entry point for background task in a nanokernel-only system,
* or the idle task in a microkernel system
*/
extern void main(void);
/* constructor initialization */
extern void _Ctors(void);
@ -116,32 +109,31 @@ extern void _Ctors(void);
#define initialize_nano_timeouts() do { } while ((0))
#endif
#ifdef CONFIG_NANOKERNEL
/**
*
* In the nanokernel only configuration we still want to run the
* app_{early,late}_init levels to maintain the correct semantics. In
* a microkernel configuration these init levels are run in the
* microkernel initialization.
* @brief Mainline for nanokernel's background task
*
* This routine completes kernel initialization by invoking the remaining
* init functions, then invokes application's main() routine.
*
* @return N/A
*/
#ifdef CONFIG_NANOKERNEL
static void _main(void)
{
_sys_device_do_config_level(NANO_EARLY);
_sys_device_do_config_level(NANO_LATE);
_sys_device_do_config_level(APP_EARLY);
_sys_device_do_config_level(APP_EARLY);
extern void main(void);
main();
}
#else
static void _main(void)
{
_sys_device_do_config_level(NANO_EARLY);
_sys_device_do_config_level(NANO_LATE);
main();
}
/* microkernel has its own implementation of _main() */
extern void _main(void);
#endif
/**
@ -191,8 +183,8 @@ static void nano_init(struct tcs *dummyOutContext)
#endif
/*
* Initialize the thread control block (TCS) for the background task
* (or idle task). The entry point for this thread is 'main'.
* Initialize the thread control block (TCS) for the main task (either
* background or idle task). The entry point for this thread is '_main'.
*/
_nanokernel.task = (struct tcs *) main_task_stack;
@ -306,7 +298,7 @@ FUNC_NORETURN void _Cstart(void)
PRINT_BOOT_BANNER();
/* context switch into background thread (entry function is main()) */
/* context switch to main task (entry function is _main()) */
_nano_fiber_swap();