This closes #13. Restructure signal handling logic in 'sim' to make it similar to interrupts on real hardware. This allows other interrupt sources beyond just timers in sim (e.g. reads/write using aio).
Switch the interval timer from ITIMER_VIRTUAL to ITIMER_REAL. This allows us to yield when we are idle and still get track passage of time faithfully (to do this with ITIMER_VIRTUAL requires busy waiting in the idle loop). This change coupled with using 'sigsuspend()' in the idle loop gets the CPU utilization from 100% to 4% at a timer frequency of 1000hz. A detailed explanation of how context switching works with signals follows: A voluntary context switch ends up with 'os_sched()' entering the critical section and doing a 'longjmp()' to the task being scheduled. The new task returns via 'os_sched()' and exits the critical section on its way out. An involuntary context switch starts with a signal handler that enters a critical section implicitly because all signals are masked when the handler is executing. This in turn means that 'os_sched()' is running in a nested critical section. The interrupted task remains on the run queue and resumes execution in the signal handler when it runs again. The cpu executes with signals/interrupts blocked until the handler returns at which time the interrupted task gets control again. Project: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/repo Commit: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/commit/9a0f9aff Tree: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/tree/9a0f9aff Diff: http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/diff/9a0f9aff Branch: refs/heads/master Commit: 9a0f9aff1c72feb4331b01035e1c7547b65380b2 Parents: f91d760 Author: Neel Natu <n...@nahannisys.com> Authored: Mon Mar 7 17:16:40 2016 -0800 Committer: wes3 <w...@micosa.io> Committed: Mon Mar 7 20:44:46 2016 -0800 ---------------------------------------------------------------------- libs/os/include/os/arch/cortex_m0/os/os_arch.h | 1 + libs/os/include/os/arch/cortex_m4/os/os_arch.h | 1 + libs/os/include/os/arch/sim/os/os_arch.h | 3 +- libs/os/src/arch/cortex_m0/os_arch_arm.c | 5 + libs/os/src/arch/cortex_m4/os_arch_arm.c | 5 + libs/os/src/arch/sim/os_arch_sim.c | 263 +++++++++----------- libs/os/src/os.c | 1 + 7 files changed, 135 insertions(+), 144 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/include/os/arch/cortex_m0/os/os_arch.h ---------------------------------------------------------------------- diff --git a/libs/os/include/os/arch/cortex_m0/os/os_arch.h b/libs/os/include/os/arch/cortex_m0/os/os_arch.h index b64534e..348a33a 100755 --- a/libs/os/include/os/arch/cortex_m0/os/os_arch.h +++ b/libs/os/include/os/arch/cortex_m0/os/os_arch.h @@ -68,6 +68,7 @@ os_error_t os_arch_os_start(void); void os_set_env(void); void os_arch_init_task_stack(os_stack_t *sf); void os_default_irq_asm(void); +void os_arch_idle(void); /* External function prototypes supplied by BSP */ void os_bsp_systick_init(uint32_t os_ticks_per_sec); http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/include/os/arch/cortex_m4/os/os_arch.h ---------------------------------------------------------------------- diff --git a/libs/os/include/os/arch/cortex_m4/os/os_arch.h b/libs/os/include/os/arch/cortex_m4/os/os_arch.h index 0a3a507..299d95f 100755 --- a/libs/os/include/os/arch/cortex_m4/os/os_arch.h +++ b/libs/os/include/os/arch/cortex_m4/os/os_arch.h @@ -68,6 +68,7 @@ os_error_t os_arch_os_start(void); void os_set_env(void); void os_arch_init_task_stack(os_stack_t *sf); void os_default_irq_asm(void); +void os_arch_idle(void); /* External function prototypes supplied by BSP */ void os_bsp_systick_init(uint32_t os_tick_per_sec); http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/include/os/arch/sim/os/os_arch.h ---------------------------------------------------------------------- diff --git a/libs/os/include/os/arch/sim/os/os_arch.h b/libs/os/include/os/arch/sim/os/os_arch.h index 68c835c..0934ab1 100644 --- a/libs/os/include/os/arch/sim/os/os_arch.h +++ b/libs/os/include/os/arch/sim/os/os_arch.h @@ -54,10 +54,11 @@ os_stack_t *os_arch_task_stack_init(struct os_task *, os_stack_t *, int); void os_arch_ctx_sw(struct os_task *); void os_arch_ctx_sw_isr(struct os_task *); os_sr_t os_arch_save_sr(void); -void os_arch_restore_sr(int); +void os_arch_restore_sr(os_sr_t sr); os_error_t os_arch_os_init(void); void os_arch_os_stop(void); os_error_t os_arch_os_start(void); +void os_arch_idle(void); void os_bsp_init(void); http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/src/arch/cortex_m0/os_arch_arm.c ---------------------------------------------------------------------- diff --git a/libs/os/src/arch/cortex_m0/os_arch_arm.c b/libs/os/src/arch/cortex_m0/os_arch_arm.c index 1fd719b..ce5efd5 100755 --- a/libs/os/src/arch/cortex_m0/os_arch_arm.c +++ b/libs/os/src/arch/cortex_m0/os_arch_arm.c @@ -336,3 +336,8 @@ os_arch_os_start(void) return err; } +void +os_arch_idle(void) +{ + return; +} http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/src/arch/cortex_m4/os_arch_arm.c ---------------------------------------------------------------------- diff --git a/libs/os/src/arch/cortex_m4/os_arch_arm.c b/libs/os/src/arch/cortex_m4/os_arch_arm.c index 64ba05e..439d7e7 100755 --- a/libs/os/src/arch/cortex_m4/os_arch_arm.c +++ b/libs/os/src/arch/cortex_m4/os_arch_arm.c @@ -349,3 +349,8 @@ os_arch_os_start(void) return err; } +void +os_arch_idle(void) +{ + return; +} http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/src/arch/sim/os_arch_sim.c ---------------------------------------------------------------------- diff --git a/libs/os/src/arch/sim/os_arch_sim.c b/libs/os/src/arch/sim/os_arch_sim.c index 18e40a1..9e08ea1 100644 --- a/libs/os/src/arch/sim/os_arch_sim.c +++ b/libs/os/src/arch/sim/os_arch_sim.c @@ -36,7 +36,6 @@ struct stack_frame { int sf_mainsp; /* stack on which main() is executing */ sigjmp_buf sf_jb; - int sf_sigsblocked; struct os_task *sf_task; }; @@ -49,47 +48,15 @@ CTASSERT(offsetof(struct stack_frame, sf_jb) == 4); extern void os_arch_frame_init(struct stack_frame *sf); -#define CTX_SWITCH_ISR (1) -#define CTX_SWITCH_TASK (2) - -#define ISR_BLOCK_OFF (0) -#define ISR_BLOCK_ON (1) - #define sim_setjmp(__jb) sigsetjmp(__jb, 0) #define sim_longjmp(__jb, __ret) siglongjmp(__jb, __ret) -sigset_t g_sigset; -volatile int g_block_isr = ISR_BLOCK_OFF; - -static volatile int g_block_isr_on = ISR_BLOCK_ON; -static volatile int g_block_isr_off = ISR_BLOCK_OFF; - -static int g_pending_ticks = 0; - -static void -isr_state(volatile int *state, volatile int *ostate) -{ - if (ostate) { - *ostate = g_block_isr; - } +#define OS_ASSERT_CRITICAL() (assert(os_arch_in_critical())) - if (state) { - g_block_isr = *state; - } -} +#define OS_USEC_PER_TICK (1000000 / OS_TICKS_PER_SEC) - -static void -sigs_unblock(void) -{ - sigprocmask(SIG_UNBLOCK, &g_sigset, NULL); -} - -static void -sigs_block(void) -{ - sigprocmask(SIG_BLOCK, &g_sigset, NULL); -} +static int os_arch_in_critical(void); +static sigset_t allsigs, nosigs; /* * Called from 'os_arch_frame_init()' when setjmp returns indirectly via @@ -100,14 +67,17 @@ os_arch_task_start(struct stack_frame *sf, int rc) { struct os_task *task; - task = sf->sf_task; - - isr_state(&g_block_isr_off, NULL); - - if (rc == CTX_SWITCH_ISR) { - sigs_unblock(); - } + /* + * Interrupts are disabled when a task starts executing. This happens in + * two different ways: + * - via os_arch_os_start() for the first task. + * - via os_sched() for all other tasks. + * + * Enable interrupts before starting the task. + */ + OS_EXIT_CRITICAL(0); + task = sf->sf_task; task->t_func(task->t_arg); /* This should never return */ @@ -120,12 +90,9 @@ os_arch_task_stack_init(struct os_task *t, os_stack_t *stack_top, int size) struct stack_frame *sf; sf = (struct stack_frame *) ((uint8_t *) stack_top - sizeof(*sf)); - sf->sf_sigsblocked = 0; sf->sf_task = t; - isr_state(&g_block_isr_on, NULL); os_arch_frame_init(sf); - isr_state(&g_block_isr_off, NULL); return ((os_stack_t *)sf); } @@ -137,15 +104,14 @@ os_arch_ctx_sw(struct os_task *next_t) struct stack_frame *sf; int rc; + OS_ASSERT_CRITICAL(); t = os_sched_get_current_task(); if (t) { sf = (struct stack_frame *) t->t_stackptr; rc = sim_setjmp(sf->sf_jb); if (rc != 0) { - if (rc == CTX_SWITCH_ISR) { - sigs_unblock(); - } + OS_ASSERT_CRITICAL(); return; } } @@ -155,136 +121,147 @@ os_arch_ctx_sw(struct os_task *next_t) os_sched_set_current_task(next_t); sf = (struct stack_frame *) next_t->t_stackptr; - /* block signals if the task we switch to expects them blocked. */ - if (sf->sf_sigsblocked) { - sigs_block(); - rc = CTX_SWITCH_ISR; - } else { - rc = CTX_SWITCH_TASK; - } - - sim_longjmp(sf->sf_jb, rc); + sim_longjmp(sf->sf_jb, 1); } void os_arch_ctx_sw_isr(struct os_task *next_t) { - struct os_task *t; - struct stack_frame *sf; - int isr_ctx; - volatile int block_isr_off; - int rc; + os_arch_ctx_sw(next_t); +} - block_isr_off = g_block_isr_off; +/* + * Disable signals and enter a critical section. + * + * Returns 1 if signals were already blocked and 0 otherwise. + */ +os_sr_t +os_arch_save_sr(void) +{ + int error; + sigset_t omask; - t = os_sched_get_current_task(); - if (t) { - sf = (struct stack_frame *) t->t_stackptr; - - /* block signals coming from an interrupt context */ - sf->sf_sigsblocked = 1; + error = sigprocmask(SIG_BLOCK, &allsigs, &omask); + assert(error == 0); - isr_state(&g_block_isr_on, &isr_ctx); + return (omask == allsigs); +} - rc = sim_setjmp(sf->sf_jb); - if (rc != 0) { - sf->sf_sigsblocked = 0; - isr_state(&block_isr_off, NULL); - return; - } - } +void +os_arch_restore_sr(os_sr_t osr) +{ + int error; - isr_state(&block_isr_off, NULL); + OS_ASSERT_CRITICAL(); + assert(osr == 0 || osr == 1); - os_sched_ctx_sw_hook(next_t); + if (osr == 1) { + /* Exiting a nested critical section */ + return; + } - os_sched_set_current_task(next_t); - - sf = (struct stack_frame *) next_t->t_stackptr; - sim_longjmp(sf->sf_jb, CTX_SWITCH_ISR); + error = sigprocmask(SIG_UNBLOCK, &allsigs, NULL); + assert(error == 0); } -os_sr_t -os_arch_save_sr(void) +static int +os_arch_in_critical(void) { - int isr_ctx; + int error; + sigset_t omask; - isr_state(&g_block_isr_on, &isr_ctx); + error = sigprocmask(SIG_SETMASK, NULL, &omask); + assert(error == 0); - return (isr_ctx); + return (omask == allsigs); } void -os_arch_restore_sr(int isr_ctx) +os_arch_idle(void) { - if (isr_ctx == ISR_BLOCK_ON) { - return; - } else { - isr_state(&g_block_isr_off, NULL); - } + assert(!os_arch_in_critical()); + + sigsuspend(&nosigs); /* Wait for a signal to wake us up */ } static void timer_handler(int sig); +static struct { + int num; + void (*handler)(int sig); +} signals[] = { + { SIGALRM, timer_handler }, +}; + +#define NUMSIGS (sizeof(signals)/sizeof(signals[0])) + static void -initialize_signals(void) +signals_init(void) { + int i, error; struct sigaction sa; - sigemptyset(&g_sigset); - sigaddset(&g_sigset, SIGALRM); - sigaddset(&g_sigset, SIGVTALRM); - - memset(&sa, 0, sizeof sa); - sa.sa_handler = timer_handler; + sigemptyset(&nosigs); + sigemptyset(&allsigs); + for (i = 0; i < NUMSIGS; i++) { + sigaddset(&allsigs, signals[i].num); + } - sigaction(SIGALRM, &sa, NULL); - sigaction(SIGVTALRM, &sa, NULL); + for (i = 0; i < NUMSIGS; i++) { + memset(&sa, 0, sizeof sa); + sa.sa_handler = signals[i].handler; + sa.sa_mask = allsigs; + error = sigaction(signals[i].num, &sa, NULL); + assert(error == 0); + } } static void -cancel_signals(void) +signals_cleanup(void) { + int i, error; struct sigaction sa; - memset(&sa, 0, sizeof sa); - sa.sa_handler = SIG_DFL; - - sigaction(SIGALRM, &sa, NULL); - sigaction(SIGVTALRM, &sa, NULL); + for (i = 0; i < NUMSIGS; i++) { + memset(&sa, 0, sizeof sa); + sa.sa_handler = SIG_DFL; + error = sigaction(signals[i].num, &sa, NULL); + assert(error == 0); + } } static void timer_handler(int sig) { + struct timeval time_now, time_diff; + int ticks; + static struct timeval time_last; static int time_inited; - struct timeval time_now, time_diff; - int isr_ctx; if (!time_inited) { gettimeofday(&time_last, NULL); time_inited = 1; } - isr_state(NULL, &isr_ctx); - if (isr_ctx == ISR_BLOCK_ON) { - ++g_pending_ticks; - return; - } - gettimeofday(&time_now, NULL); timersub(&time_now, &time_last, &time_diff); - g_pending_ticks = time_diff.tv_usec / 1000; + ticks = time_diff.tv_sec * OS_TICKS_PER_SEC; + ticks += time_diff.tv_usec / OS_USEC_PER_TICK; - while (--g_pending_ticks >= 0) { + while (--ticks >= 0) { os_time_tick(); os_callout_tick(); } - time_last = time_now; - g_pending_ticks = 0; + /* + * Update 'time_last' but account for the remainder usecs that did not + * contribute towards whole 'ticks'. + */ + time_diff.tv_sec = 0; + time_diff.tv_usec %= OS_USEC_PER_TICK; + timersub(&time_now, &time_diff, &time_last); os_sched_os_timer_exp(); os_sched(NULL, 1); @@ -296,21 +273,14 @@ start_timer(void) struct itimerval it; int rc; - initialize_signals(); - - /* 1 msec OS tick */ memset(&it, 0, sizeof(it)); it.it_value.tv_sec = 0; - it.it_value.tv_usec = 1000; + it.it_value.tv_usec = OS_USEC_PER_TICK; it.it_interval.tv_sec = 0; - it.it_interval.tv_usec = 1000; + it.it_interval.tv_usec = OS_USEC_PER_TICK; - rc = setitimer(ITIMER_VIRTUAL, &it, NULL); - if (rc != 0) { - const char msg[] = "Cannot set itimer"; - write(2, msg, sizeof(msg)); - _exit(1); - } + rc = setitimer(ITIMER_REAL, &it, NULL); + assert(rc == 0); } static void @@ -321,14 +291,8 @@ stop_timer(void) memset(&it, 0, sizeof(it)); - rc = setitimer(ITIMER_VIRTUAL, &it, NULL); - if (rc != 0) { - const char msg[] = "Cannot stop itimer"; - write(2, msg, sizeof(msg)); - _exit(1); - } - - cancel_signals(); + rc = setitimer(ITIMER_REAL, &it, NULL); + assert(rc == 0); } os_error_t @@ -352,7 +316,19 @@ os_arch_os_start(void) { struct stack_frame *sf; struct os_task *t; + os_sr_t sr; + + /* Setup all interrupt handlers */ + signals_init(); + + /* + * Disable interrupts before enabling any interrupt sources. Pending + * interrupts will be recognized when the first task starts executing. + */ + OS_ENTER_CRITICAL(sr); + assert(sr == 0); + /* Enable the interrupt sources */ start_timer(); t = os_sched_next_task(); @@ -361,7 +337,7 @@ os_arch_os_start(void) g_os_started = 1; sf = (struct stack_frame *) t->t_stackptr; - sim_longjmp(sf->sf_jb, CTX_SWITCH_TASK); + sim_longjmp(sf->sf_jb, 1); return 0; } @@ -374,5 +350,6 @@ void os_arch_os_stop(void) { stop_timer(); + signals_cleanup(); g_os_started = 0; } http://git-wip-us.apache.org/repos/asf/incubator-mynewt-larva/blob/9a0f9aff/libs/os/src/os.c ---------------------------------------------------------------------- diff --git a/libs/os/src/os.c b/libs/os/src/os.c index dd43cf0..078800a 100644 --- a/libs/os/src/os.c +++ b/libs/os/src/os.c @@ -37,6 +37,7 @@ os_idle_task(void *arg) /* For now, idle task simply increments a counter to show it is running. */ while (1) { ++g_os_idle_ctr; + os_arch_idle(); } }
