diff options
Diffstat (limited to 'src/kernel/task.c')
| -rw-r--r-- | src/kernel/task.c | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/src/kernel/task.c b/src/kernel/task.c index 304e608..b6f4fc1 100644 --- a/src/kernel/task.c +++ b/src/kernel/task.c @@ -146,8 +146,9 @@ void task_purge(void) } // Free this thread's stack, and task data. - // Since we're single core, no one else can claim this memory until - // a task switch, after which we're done with this memory anyway. + // The scheduler still needs to use the data we're about to free; however, + // our single-core implementation keeps us safe from anyone else claiming + // this memory in the meantime. free(task_current->stack); free(task_current->heap); free(task_current); @@ -168,7 +169,8 @@ void task_doexit(void) /** * 'Prepares' task for running. - * Calls the task's main code, setting task_doexit() (_exit) as the return point. + * Calls the task's main code after making task_doexit() (_exit) main's return + * point. */ __attribute__ ((naked)) void task_crt0(void) @@ -191,7 +193,7 @@ task_t *task_create(void (*code)(void), uint16_t stackSize) t->heap = 0; t->stack = (uint32_t *)malloc(stackSize); - void *sp = (uint8_t *)t->stack + stackSize - 68; // excep. stack + regs + void *sp = (uint8_t *)t->stack + stackSize - 68; // exception stack + regs t->sp = sp; /* @@ -215,6 +217,7 @@ task_t *task_create(void (*code)(void), uint16_t stackSize) void task_init(void (*init)(void), uint16_t stackSize) { + // Create a dummy current task that we'll "exit" from task_current = (task_t *)malloc(sizeof(task_t)); task_current->next = 0; task_current->stack = 0; // free() is called on this @@ -222,10 +225,12 @@ void task_init(void (*init)(void), uint16_t stackSize) task_current->status.state = TASK_SLEEPING; task_current->status.value = 1000; + // Place the init task in the queue to take the dummy task's place task_queue = task_create(init, stackSize); task_disable = 0; + // Enter userspace process mode // bit 0 - priv, bit 1 - psp/msp asm("\ isb; \ @@ -237,7 +242,7 @@ void task_init(void (*init)(void), uint16_t stackSize) msr control, r0; \ "); - // exit the current (fake) task + // Exit the current (fake) task task_doexit(); } @@ -307,9 +312,9 @@ void PendSV_Handler(void) if (task_disable != 0) asm("bx lr"); - // TODO get back to c, implement task sleeping + // TODO get back to c, implement task sleeping TODO did we do this? - // Save current stack pointer + // Finish saving current state asm("\ mrs r0, psp; \ isb; \ |