X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Fkern%2Fproc.c;h=623c1d3fb5d87dba4ceb91b5c35ddcd6f85749c8;hb=d9d931610bca1df6ceb9227eacc9ff2c7f89b77a;hp=32e3afe8a2f50b317af65291fa9f0d86fcc3f7b2;hpb=dc9c2e09cf5e9837cdd3106c57db749301c5bf95;p=bertos.git diff --git a/bertos/kern/proc.c b/bertos/kern/proc.c index 32e3afe8..623c1d3f 100644 --- a/bertos/kern/proc.c +++ b/bertos/kern/proc.c @@ -26,180 +26,273 @@ * invalidate any other reasons why the executable file might be covered by * the GNU General Public License. * - * Copyright 2001,2004 Develer S.r.l. (http://www.develer.com/) - * Copyright 1999,2000,2001 Bernie Innocenti - * + * Copyright 2001, 2004 Develer S.r.l. (http://www.develer.com/) + * Copyright 1999, 2000, 2001, 2008 Bernie Innocenti * --> * - * \brief Simple realtime multitasking scheduler. - * Context switching is only done cooperatively. - * - * \version $Id$ + * \brief Simple cooperative multitasking scheduler. * * \author Bernie Innocenti * \author Stefano Fedrigo */ - #include "proc_p.h" #include "proc.h" -#include "cfg/cfg_arch.h" /* ARCH_EMUL */ -#include +#include "cfg/cfg_proc.h" +#define LOG_LEVEL KERN_LOG_LEVEL +#define LOG_FORMAT KERN_LOG_FORMAT +#include + +#include "cfg/cfg_monitor.h" +#include // ROUND_UP2 #include -#include /* ABS() */ +#include // CONFIG_DEPEND() #include #include #include +#include -#include +#if CONFIG_KERN_HEAP + #include +#endif #include /* memset() */ +#define PROC_SIZE_WORDS (ROUND_UP2(sizeof(Process), sizeof(cpu_stack_t)) / sizeof(cpu_stack_t)) + /** * CPU dependent context switching routines. * - * \note This function *MUST* preserve also the status of the interrupts. + * Saving and restoring the context on the stack is done by a CPU-dependent + * support routine which usually needs to be written in assembly. */ -EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp); -EXTERN_C int asm_switch_version(void); +EXTERN_C void asm_switch_context(cpu_stack_t **new_sp, cpu_stack_t **save_sp); /* - * The scheduer tracks ready and waiting processes - * by enqueuing them in these lists. A pointer to the currently - * running process is stored in the CurrentProcess pointer. + * The scheduer tracks ready processes by enqueuing them in the + * ready list. * - * NOTE: these variables are protected by DI/EI locking + * \note Access to the list must occur while interrupts are disabled. */ -REGISTER Process *CurrentProcess; -REGISTER List ProcReadyList; - +REGISTER List proc_ready_list; -#if CONFIG_KERN_PREEMPTIVE /* - * The time sharing scheduler forces a task switch when - * the current process has consumed its quantum. + * Holds a pointer to the TCB of the currently running process. + * + * \note User applications should use proc_current() to retrieve this value. */ -uint16_t Quantum; -#endif +REGISTER Process *current_process; +/** The main process (the one that executes main()). */ +static struct Process main_process; -/* In Win32 we must emulate stack on the real process stack */ -#if (ARCH & ARCH_EMUL) -extern List StackFreeList; -#endif +#if CONFIG_KERN_HEAP -/** The main process (the one that executes main()). */ -struct Process MainProcess; +/** + * Local heap dedicated to allocate the memory used by the processes. + */ +static HEAP_DEFINE_BUF(heap_buf, CONFIG_KERN_HEAP_SIZE); +static Heap proc_heap; +/* + * Keep track of zombie processes (processes that are exiting and need to + * release some resources). + * + * \note Access to the list must occur while kernel preemption is disabled. + */ +static List zombie_list; + +#endif /* CONFIG_KERN_HEAP */ -static void proc_init_struct(Process *proc) +static void proc_initStruct(Process *proc) { /* Avoid warning for unused argument. */ (void)proc; #if CONFIG_KERN_SIGNALS proc->sig_recv = 0; -#endif - -#if CONFIG_KERN_PREEMPTIVE - proc->forbid_cnt = 0; + proc->sig_wait = 0; #endif #if CONFIG_KERN_HEAP proc->flags = 0; #endif + +#if CONFIG_KERN_PRI + proc->link.pri = 0; +#endif } MOD_DEFINE(proc); void proc_init(void) { - LIST_INIT(&ProcReadyList); + LIST_INIT(&proc_ready_list); -#if CONFIG_KERN_MONITOR - monitor_init(); +#if CONFIG_KERN_HEAP + LIST_INIT(&zombie_list); + heap_init(&proc_heap, heap_buf, sizeof(heap_buf)); #endif - - /* We "promote" the current context into a real process. The only thing we have + /* + * We "promote" the current context into a real process. The only thing we have * to do is create a PCB and make it current. We don't need to setup the stack * pointer because it will be written the first time we switch to another process. */ - proc_init_struct(&MainProcess); - CurrentProcess = &MainProcess; + proc_initStruct(&main_process); + current_process = &main_process; - /* Make sure the assembly routine is up-to-date with us */ - ASSERT(asm_switch_version() == 1); +#if CONFIG_KERN_MONITOR + monitor_init(); + monitor_add(current_process, "main"); +#endif MOD_INIT(proc); } +#if CONFIG_KERN_HEAP + +/** + * Free all the resources of all zombie processes previously added to the zombie + * list. + */ +static void proc_freeZombies(void) +{ + Process *proc; + + while (1) + { + PROC_ATOMIC(proc = (Process *)list_remHead(&zombie_list)); + if (proc == NULL) + return; + + if (proc->flags & PF_FREESTACK) + { + PROC_ATOMIC(heap_freemem(&proc_heap, proc->stack_base, + proc->stack_size + PROC_SIZE_WORDS * sizeof(cpu_stack_t))); + } + } +} + +/** + * Enqueue a process in the zombie list. + */ +static void proc_addZombie(Process *proc) +{ + Node *node; +#if CONFIG_KERN_PREEMPT + ASSERT(!proc_preemptAllowed()); +#endif + +#if CONFIG_KERN_PRI + node = &(proc)->link.link; +#else + node = &(proc)->link; +#endif + LIST_ASSERT_VALID(&zombie_list); + ADDTAIL(&zombie_list, node); +} + +#endif /* CONFIG_KERN_HEAP */ + /** * Create a new process, starting at the provided entry point. * + * + * \note The function + * \code + * proc_new(entry, data, stacksize, stack) + * \endcode + * is a more convenient way to create a process, as you don't have to specify + * the name. + * * \return Process structure of new created process * if successful, NULL otherwise. */ -struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(void), iptr_t data, size_t stack_size, cpustack_t *stack_base) +struct Process *proc_new_with_name(UNUSED_ARG(const char *, name), void (*entry)(void), iptr_t data, size_t stack_size, cpu_stack_t *stack_base) { Process *proc; - size_t i; - const size_t PROC_SIZE_WORDS = ROUND2(sizeof(Process), sizeof(cpustack_t)) / sizeof(cpustack_t); + LOG_INFO("name=%s", name); #if CONFIG_KERN_HEAP bool free_stack = false; -#endif -#if (ARCH & ARCH_EMUL) - /* Ignore stack provided by caller and use the large enough default instead. */ - stack_base = (cpustack_t *)list_remHead(&StackFreeList); + /* + * Free up resources of a zombie process. + * + * We're implementing a kind of lazy garbage collector here for + * efficiency reasons: we can avoid to introduce overhead into another + * kernel task dedicated to free up resources (e.g., idle) and we're + * not introducing any overhead into the scheduler after a context + * switch (that would be *very* bad, because the scheduler runs with + * IRQ disabled). + * + * In this way we are able to release the memory of the zombie tasks + * without disabling IRQs and without introducing any significant + * overhead in any other kernel task. + */ + proc_freeZombies(); - stack_size = CONFIG_PROC_DEFSTACKSIZE; -#elif CONFIG_KERN_HEAP /* Did the caller provide a stack for us? */ if (!stack_base) { /* Did the caller specify the desired stack size? */ if (!stack_size) - stack_size = CONFIG_PROC_DEFSTACKSIZE + sizeof(Process); + stack_size = KERN_MINSTACKSIZE; /* Allocate stack dinamically */ - if (!(stack_base = heap_alloc(stack_size))) + PROC_ATOMIC(stack_base = + (cpu_stack_t *)heap_allocmem(&proc_heap, stack_size)); + if (stack_base == NULL) return NULL; free_stack = true; } -#else + +#else // CONFIG_KERN_HEAP + /* Stack must have been provided by the user */ - ASSERT(stack_base); + ASSERT_VALID_PTR(stack_base); ASSERT(stack_size); -#endif + +#endif // CONFIG_KERN_HEAP #if CONFIG_KERN_MONITOR - /* Fill-in the stack with a special marker to help debugging */ - memset(stack_base, CONFIG_KERN_STACKFILLCODE, stack_size / sizeof(cpustack_t)); + /* + * Fill-in the stack with a special marker to help debugging. + * On 64bit platforms, CONFIG_KERN_STACKFILLCODE is larger + * than an int, so the (int) cast is required to silence the + * warning for truncating its size. + */ + memset(stack_base, (int)CONFIG_KERN_STACKFILLCODE, stack_size); #endif /* Initialize the process control block */ if (CPU_STACK_GROWS_UPWARD) { - proc = (Process*)stack_base; + proc = (Process *)stack_base; proc->stack = stack_base + PROC_SIZE_WORDS; + // On some architecture stack should be aligned, so we do it. + proc->stack = (cpu_stack_t *)((uintptr_t)proc->stack + (sizeof(cpu_aligned_stack_t) - ((uintptr_t)proc->stack % sizeof(cpu_aligned_stack_t)))); if (CPU_SP_ON_EMPTY_SLOT) proc->stack++; } else { - proc = (Process*)(stack_base + stack_size / sizeof(cpustack_t) - PROC_SIZE_WORDS); - proc->stack = (cpustack_t*)proc; + proc = (Process *)(stack_base + stack_size / sizeof(cpu_stack_t) - PROC_SIZE_WORDS); + // On some architecture stack should be aligned, so we do it. + proc->stack = (cpu_stack_t *)((uintptr_t)proc - ((uintptr_t)proc % sizeof(cpu_aligned_stack_t))); if (CPU_SP_ON_EMPTY_SLOT) proc->stack--; } + /* Ensure stack is aligned */ + ASSERT((uintptr_t)proc->stack % sizeof(cpu_aligned_stack_t) == 0); - proc_init_struct(proc); + stack_size -= PROC_SIZE_WORDS * sizeof(cpu_stack_t); + proc_initStruct(proc); proc->user_data = data; -#if CONFIG_KERN_HEAP | CONFIG_KERN_MONITOR | (ARCH & ARCH_EMUL) +#if CONFIG_KERN_HEAP | CONFIG_KERN_MONITOR proc->stack_base = stack_base; proc->stack_size = stack_size; #if CONFIG_KERN_HEAP @@ -207,26 +300,41 @@ struct Process *proc_new_with_name(UNUSED(const char *, name), void (*entry)(voi proc->flags |= PF_FREESTACK; #endif #endif + proc->user_entry = entry; + CPU_CREATE_NEW_STACK(proc->stack); - /* Initialize process stack frame */ - CPU_PUSH_CALL_CONTEXT(proc->stack, proc_exit); - CPU_PUSH_CALL_CONTEXT(proc->stack, entry); - - /* Push a clean set of CPU registers for asm_switch_context() */ - for (i = 0; i < CPU_SAVED_REGS_CNT; i++) - CPU_PUSH_WORD(proc->stack, CPU_REG_INIT_VALUE(i)); +#if CONFIG_KERN_MONITOR + monitor_add(proc, name); +#endif /* Add to ready list */ ATOMIC(SCHED_ENQUEUE(proc)); + return proc; +} + +/** + * Return the name of the specified process. + * + * NULL is a legal argument and will return the name "". + */ +const char *proc_name(struct Process *proc) +{ #if CONFIG_KERN_MONITOR - monitor_add(proc, name); + return proc ? proc->monitor.name : ""; +#else + (void)proc; + return "---"; #endif +} - return proc; +/// Return the name of the currently running process +const char *proc_currentName(void) +{ + return proc_name(proc_current()); } -/** Rename a process */ +/// Rename a process void proc_rename(struct Process *proc, const char *name) { #if CONFIG_KERN_MONITOR @@ -237,184 +345,147 @@ void proc_rename(struct Process *proc, const char *name) } +#if CONFIG_KERN_PRI /** - * System scheduler: pass CPU control to the next process in - * the ready queue. + * Change the scheduling priority of a process. + * + * Process piorities are signed ints, whereas a larger integer value means + * higher scheduling priority. The default priority for new processes is 0. + * The idle process runs with the lowest possible priority: INT_MIN. + * + * A process with a higher priority always preempts lower priority processes. + * Processes of equal priority share the CPU time according to a simple + * round-robin policy. + * + * As a general rule to maximize responsiveness, compute-bound processes + * should be assigned negative priorities and tight, interactive processes + * should be assigned positive priorities. * - * Saving and restoring the context on the stack is done - * by a CPU-dependent support routine which must usually be - * written in assembly. + * To avoid interfering with system background activities such as input + * processing, application processes should remain within the range -10 + * and +10. */ -void proc_schedule(void) +void proc_setPri(struct Process *proc, int pri) { - struct Process *old_process; - cpuflags_t flags; + if (proc->link.pri == pri) + return; - /* Remember old process to save its context later */ - old_process = CurrentProcess; + proc->link.pri = pri; -#ifdef IRQ_RUNNING - /* Scheduling in interrupts is a nono. */ - ASSERT(!IRQ_RUNNING()); -#endif + if (proc != current_process) + ATOMIC(sched_reenqueue(proc)); +} +#endif // CONFIG_KERN_PRI - /* Poll on the ready queue for the first ready process */ - IRQ_SAVE_DISABLE(flags); - while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList))) - { - /* - * Make sure we physically reenable interrupts here, no matter what - * the current task status is. This is important because if we - * are idle-spinning, we must allow interrupts, otherwise no - * process will ever wake up. - * - * During idle-spinning, an interrupt can occur and it may - * modify \p ProcReadyList. To ensure that compiler reload this - * variable every while cycle we call CPU_MEMORY_BARRIER. - * The memory barrier ensure that all variables used in this context - * are reloaded. - * \todo If there was a way to write sig_wait() so that it does not - * disable interrupts while waiting, there would not be any - * reason to do this. - */ - IRQ_ENABLE; - CPU_IDLE; - MEMORY_BARRIER; - IRQ_DISABLE; - } - IRQ_RESTORE(flags); +INLINE void proc_run(void) +{ + void (*entry)(void) = current_process->user_entry; + LOG_INFO("New process starting at %p", entry); + entry(); +} + +/** + * Entry point for all the processes. + */ +void proc_entry(void) +{ /* - * Optimization: don't switch contexts when the active - * process has not changed. + * Return from a context switch assumes interrupts are disabled, so + * we need to explicitly re-enable them as soon as possible. */ - if (CurrentProcess != old_process) - { - cpustack_t *dummy; - -#if CONFIG_KERN_PREEMPTIVE - /* Reset quantum for this process */ - Quantum = CONFIG_KERN_QUANTUM; -#endif - - /* Save context of old process and switch to new process. If there is no - * old process, we save the old stack pointer into a dummy variable that - * we ignore. In fact, this happens only when the old process has just - * exited. - * TODO: Instead of physically clearing the process at exit time, a zombie - * list should be created. - */ - asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy); - } - - /* This RET resumes the execution on the new process */ + IRQ_ENABLE; + /* Call the actual process's entry point */ + proc_run(); + proc_exit(); } - /** * Terminate the current process */ void proc_exit(void) { + LOG_INFO("%p:%s", current_process, proc_currentName()); + #if CONFIG_KERN_MONITOR - monitor_remove(CurrentProcess); + monitor_remove(current_process); #endif + proc_forbid(); #if CONFIG_KERN_HEAP /* - * The following code is BROKEN. - * We are freeing our own stack before entering proc_schedule() - * BAJO: A correct fix would be to rearrange the scheduler with - * an additional parameter which frees the old stack/process - * after a context switch. + * Set the task as zombie, its resources will be freed in proc_new() in + * a lazy way, when another process will be created. */ - if (CurrentProcess->flags & PF_FREESTACK) - heap_free(CurrentProcess->stack_base, CurrentProcess->stack_size); - heap_free(CurrentProcess); + proc_addZombie(current_process); #endif + current_process = NULL; + proc_permit(); -#if (ARCH & ARCH_EMUL) -#warning This is wrong - /* Reinsert process stack in free list */ - ADDHEAD(&StackFreeList, (Node *)(CurrentProcess->stack - - (CONFIG_PROC_DEFSTACKSIZE / sizeof(cpustack_t)))); - - /* - * NOTE: At this point the first two words of what used - * to be our stack contain a list node. From now on, we - * rely on the compiler not reading/writing the stack. - */ -#endif /* ARCH_EMUL */ - - CurrentProcess = NULL; - proc_schedule(); - /* not reached */ -} - - -/** - * Co-operative context switch - */ -void proc_switch(void) -{ - cpuflags_t flags; - - IRQ_SAVE_DISABLE(flags); - SCHED_ENQUEUE(CurrentProcess); - IRQ_RESTORE(flags); + proc_switch(); - proc_schedule(); + /* never reached */ + ASSERT(0); } /** - * Get the pointer to the current process + * Get the pointer to the user data of the current process */ -struct Process *proc_current(void) +iptr_t proc_currentUserData(void) { - return CurrentProcess; + return current_process->user_data; } /** - * Get the pointer to the user data of the current process + * Call the scheduler and eventually replace the current running process. */ -iptr_t proc_current_user_data(void) +void proc_schedule(void) { - return CurrentProcess->user_data; -} - + Process *old_process = current_process; -#if CONFIG_KERN_PREEMPTIVE + IRQ_ASSERT_DISABLED(); -/** - * Disable preemptive task switching. - * - * The scheduler maintains a per-process nesting counter. Task switching is - * effectively re-enabled only when the number of calls to proc_permit() - * matches the number of calls to proc_forbid(). - * - * Calling functions that could sleep while task switching is disabled - * is dangerous, although supported. Preemptive task switching is - * resumed while the process is sleeping and disabled again as soon as - * it wakes up again. - * - * \sa proc_permit() - */ -void proc_forbid(void) -{ - /* No need to protect against interrupts here. */ - ++CurrentProcess->forbid_cnt; -} + /* Poll on the ready queue for the first ready process */ + LIST_ASSERT_VALID(&proc_ready_list); + while (!(current_process = (struct Process *)list_remHead(&proc_ready_list))) + { + /* + * Make sure we physically reenable interrupts here, no matter what + * the current task status is. This is important because if we + * are idle-spinning, we must allow interrupts, otherwise no + * process will ever wake up. + * + * During idle-spinning, an interrupt can occur and it may + * modify \p proc_ready_list. To ensure that compiler reload this + * variable every while cycle we call CPU_MEMORY_BARRIER. + * The memory barrier ensure that all variables used in this context + * are reloaded. + * \todo If there was a way to write sig_wait() so that it does not + * disable interrupts while waiting, there would not be any + * reason to do this. + */ + IRQ_ENABLE; + CPU_IDLE; + MEMORY_BARRIER; + IRQ_DISABLE; + } + /* + * Optimization: don't switch contexts when the active process has not + * changed. + */ + if (LIKELY(current_process != old_process)) { + cpu_stack_t *dummy; -/** - * Re-enable preemptive task switching. - * - * \sa proc_forbid() - */ -void proc_permit(void) -{ - /* No need to protect against interrupts here. */ - --CurrentProcess->forbid_cnt; + /* + * Save context of old process and switch to new process. If + * there is no old process, we save the old stack pointer into + * a dummy variable that we ignore. In fact, this happens only + * when the old process has just exited. + */ + asm_switch_context(¤t_process->stack, + old_process ? &old_process->stack : &dummy); + } + /* This RET resumes the execution on the new process */ + LOG_INFO("resuming %p:%s\n", current_process, proc_currentName()); } - -#endif /* CONFIG_KERN_PREEMPTIVE */