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stmhal: Implement a proper thread scheduler.

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This patch changes the threading implementation from simple round-robin
with busy waits on mutexs, to proper scheduling whereby threads that are
waiting on a mutex are only scheduled when the mutex becomes available.
This commit is contained in:
Damien George 2017-02-06 15:13:30 +11:00
parent f6c22a0679
commit 05a4859585
9 changed files with 236 additions and 63 deletions
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4
stmhal/main.c
View File

@ -695,6 +695,10 @@ soft_reset_exit:
can_deinit();
#endif
#if MICROPY_PY_THREAD
pyb_thread_deinit();
#endif
first_soft_reset = false;
goto soft_reset;
}

5
stmhal/modmachine.c
View File

@ -41,6 +41,7 @@
#include "extmod/vfs_fat.h"
#include "gccollect.h"
#include "irq.h"
#include "pybthread.h"
#include "rng.h"
#include "storage.h"
#include "pin.h"
@ -159,6 +160,10 @@ STATIC mp_obj_t machine_info(mp_uint_t n_args, const mp_obj_t *args) {
}
}
#if MICROPY_PY_THREAD
pyb_thread_dump();
#endif
if (n_args == 1) {
// arg given means dump gc allocation table
gc_dump_alloc_table();

14
stmhal/mpconfigport.h
View File

@ -299,7 +299,21 @@ static inline mp_uint_t disable_irq(void) {
#define MICROPY_BEGIN_ATOMIC_SECTION() disable_irq()
#define MICROPY_END_ATOMIC_SECTION(state) enable_irq(state)
#if MICROPY_PY_THREAD
#define MICROPY_EVENT_POLL_HOOK \
do { \
if (pyb_thread_enabled) { \
MP_THREAD_GIL_EXIT(); \
pyb_thread_yield(); \
MP_THREAD_GIL_ENTER(); \
} else { \
__WFI(); \
} \
} while (0);
#else
#define MICROPY_EVENT_POLL_HOOK __WFI();
#endif
// There is no classical C heap in bare-metal ports, only Python
// garbage-collected heap. For completeness, emulate C heap via

35
stmhal/mpthreadport.c
View File

@ -44,15 +44,13 @@ void mp_thread_init(void) {
void mp_thread_gc_others(void) {
mp_thread_mutex_lock(&thread_mutex, 1);
gc_collect_root((void**)&pyb_thread_cur, 1);
for (pyb_thread_t *th = pyb_thread_cur;; th = th->next) {
for (pyb_thread_t *th = pyb_thread_all; th != NULL; th = th->all_next) {
gc_collect_root((void**)&th, 1);
gc_collect_root(&th->arg, 1);
gc_collect_root(&th->stack, 1);
if (th != pyb_thread_cur) {
gc_collect_root(th->stack, th->stack_len);
}
if (th->next == pyb_thread_cur) {
break;
}
}
mp_thread_mutex_unlock(&thread_mutex);
}
@ -93,31 +91,4 @@ void mp_thread_start(void) {
void mp_thread_finish(void) {
}
void mp_thread_mutex_init(mp_thread_mutex_t *mutex) {
*mutex = 0;
}
int mp_thread_mutex_lock(mp_thread_mutex_t *mutex, int wait) {
uint32_t irq_state = disable_irq();
if (*mutex) {
// mutex is locked
if (!wait) {
enable_irq(irq_state);
return 0; // failed to lock mutex
}
while (*mutex) {
enable_irq(irq_state);
pyb_thread_yield();
irq_state = disable_irq();
}
}
*mutex = 1;
enable_irq(irq_state);
return 1; // have mutex
}
void mp_thread_mutex_unlock(mp_thread_mutex_t *mutex) {
*mutex = 0;
}
#endif // MICROPY_PY_THREAD

14
stmhal/mpthreadport.h
View File

@ -29,7 +29,7 @@
#include "py/mpthread.h"
#include "pybthread.h"
typedef uint32_t mp_thread_mutex_t;
typedef pyb_mutex_t mp_thread_mutex_t;
void mp_thread_init(void);
void mp_thread_gc_others(void);
@ -42,4 +42,16 @@ static inline struct _mp_state_thread_t *mp_thread_get_state(void) {
return pyb_thread_get_local();
}
static inline void mp_thread_mutex_init(mp_thread_mutex_t *m) {
pyb_mutex_init(m);
}
static inline int mp_thread_mutex_lock(mp_thread_mutex_t *m, int wait) {
return pyb_mutex_lock(m, wait);
}
static inline void mp_thread_mutex_unlock(mp_thread_mutex_t *m) {
pyb_mutex_unlock(m);
}
#endif // __MICROPY_INCLUDED_STMHAL_MPTHREADPORT_H__

179
stmhal/pybthread.c
View File

@ -34,29 +34,80 @@
#if MICROPY_PY_THREAD
int pyb_thread_enabled;
pyb_thread_t *pyb_thread_cur;
#define PYB_MUTEX_UNLOCKED ((void*)0)
#define PYB_MUTEX_LOCKED ((void*)1)
extern void __fatal_error(const char*);
volatile int pyb_thread_enabled;
pyb_thread_t *volatile pyb_thread_all;
pyb_thread_t *volatile pyb_thread_cur;
static inline void pyb_thread_add_to_runable(pyb_thread_t *thread) {
thread->run_prev = pyb_thread_cur->run_prev;
thread->run_next = pyb_thread_cur;
pyb_thread_cur->run_prev->run_next = thread;
pyb_thread_cur->run_prev = thread;
}
static inline void pyb_thread_remove_from_runable(pyb_thread_t *thread) {
if (thread->run_next == thread) {
__fatal_error("deadlock");
}
thread->run_prev->run_next = thread->run_next;
thread->run_next->run_prev = thread->run_prev;
}
void pyb_thread_init(pyb_thread_t *thread) {
pyb_thread_enabled = 0;
pyb_thread_all = thread;
pyb_thread_cur = thread;
pyb_thread_cur->sp = NULL; // will be set when this thread switches out
pyb_thread_cur->local_state = 0; // will be set by mp_thread_init
pyb_thread_cur->arg = NULL;
pyb_thread_cur->stack = &_heap_end;
pyb_thread_cur->stack_len = ((uint32_t)&_estack - (uint32_t)&_heap_end) / sizeof(uint32_t);
pyb_thread_cur->prev = thread;
pyb_thread_cur->next = thread;
thread->sp = NULL; // will be set when this thread switches out
thread->local_state = 0; // will be set by mp_thread_init
thread->arg = NULL;
thread->stack = &_heap_end;
thread->stack_len = ((uint32_t)&_estack - (uint32_t)&_heap_end) / sizeof(uint32_t);
thread->all_next = NULL;
thread->run_prev = thread;
thread->run_next = thread;
thread->queue_next = NULL;
}
void pyb_thread_deinit() {
uint32_t irq_state = disable_irq();
pyb_thread_enabled = 0;
pyb_thread_all = pyb_thread_cur;
pyb_thread_cur->all_next = NULL;
pyb_thread_cur->run_prev = pyb_thread_cur;
pyb_thread_cur->run_next = pyb_thread_cur;
enable_irq(irq_state);
}
STATIC void pyb_thread_terminate(void) {
uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
pyb_thread_cur->prev->next = pyb_thread_cur->next;
pyb_thread_cur->next->prev = pyb_thread_cur->prev;
if (pyb_thread_cur->next == pyb_thread_cur->prev) {
uint32_t irq_state = disable_irq();
pyb_thread_t *thread = pyb_thread_cur;
// take current thread off the run list
pyb_thread_remove_from_runable(thread);
// take current thread off the list of all threads
for (pyb_thread_t **n = (pyb_thread_t**)&pyb_thread_all;; n = &(*n)->all_next) {
if (*n == thread) {
*n = thread->all_next;
break;
}
}
// clean pointers as much as possible to help GC
thread->all_next = NULL;
thread->queue_next = NULL;
thread->stack = NULL;
if (pyb_thread_all->all_next == NULL) {
// only 1 thread left
pyb_thread_enabled = 0;
}
restore_irq_pri(irq_state);
pyb_thread_yield(); // should not return
// thread switch will occur after we enable irqs
SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
enable_irq(irq_state);
// should not return
__fatal_error("could not terminate");
}
uint32_t pyb_thread_new(pyb_thread_t *thread, void *stack, size_t stack_len, void *entry, void *arg) {
@ -77,21 +128,105 @@ uint32_t pyb_thread_new(pyb_thread_t *thread, void *stack, size_t stack_len, voi
thread->arg = arg;
thread->stack = stack;
thread->stack_len = stack_len;
uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
thread->queue_next = NULL;
uint32_t irq_state = disable_irq();
pyb_thread_enabled = 1;
thread->next = pyb_thread_cur->next;
thread->prev = pyb_thread_cur;
pyb_thread_cur->next->prev = thread;
pyb_thread_cur->next = thread;
restore_irq_pri(irq_state);
thread->all_next = pyb_thread_all;
pyb_thread_all = thread;
pyb_thread_add_to_runable(thread);
enable_irq(irq_state);
return (uint32_t)thread; // success
}
void pyb_thread_dump(void) {
if (!pyb_thread_enabled) {
printf("THREAD: only main thread\n");
} else {
printf("THREAD:\n");
for (pyb_thread_t *th = pyb_thread_all; th != NULL; th = th->all_next) {
bool runable = false;
for (pyb_thread_t *th2 = pyb_thread_cur;; th2 = th2->run_next) {
if (th == th2) {
runable = true;
break;
}
if (th2->run_next == pyb_thread_cur) {
break;
}
}
printf(" id=%p sp=%p sz=%u", th, th->stack, th->stack_len);
if (runable) {
printf(" (runable)");
}
printf("\n");
}
}
}
// should only be called from pendsv_isr_handler
void *pyb_thread_next(void *sp) {
pyb_thread_cur->sp = sp;
pyb_thread_cur = pyb_thread_cur->next;
pyb_thread_cur = pyb_thread_cur->run_next;
pyb_thread_cur->timeslice = 4; // in milliseconds
return pyb_thread_cur->sp;
}
void pyb_mutex_init(pyb_mutex_t *m) {
*m = PYB_MUTEX_UNLOCKED;
}
int pyb_mutex_lock(pyb_mutex_t *m, int wait) {
uint32_t irq_state = disable_irq();
if (*m == PYB_MUTEX_UNLOCKED) {
// mutex is available
*m = PYB_MUTEX_LOCKED;
enable_irq(irq_state);
} else {
// mutex is locked
if (!wait) {
enable_irq(irq_state);
return 0; // failed to lock mutex
}
if (*m == PYB_MUTEX_LOCKED) {
*m = pyb_thread_cur;
} else {
for (pyb_thread_t *n = *m;; n = n->queue_next) {
if (n->queue_next == NULL) {
n->queue_next = pyb_thread_cur;
break;
}
}
}
pyb_thread_cur->queue_next = NULL;
// take current thread off the run list
pyb_thread_remove_from_runable(pyb_thread_cur);
// thread switch will occur after we enable irqs
SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
enable_irq(irq_state);
// when we come back we have the mutex
}
return 1; // have mutex
}
void pyb_mutex_unlock(pyb_mutex_t *m) {
uint32_t irq_state = disable_irq();
if (*m == PYB_MUTEX_LOCKED) {
// no threads are blocked on the mutex
*m = PYB_MUTEX_UNLOCKED;
} else {
// at least one thread is blocked on this mutex
pyb_thread_t *th = *m;
if (th->queue_next == NULL) {
// no other threads are blocked
*m = PYB_MUTEX_LOCKED;
} else {
// at least one other thread is still blocked
*m = th->queue_next;
}
// put unblocked thread on runable list
pyb_thread_add_to_runable(th);
}
enable_irq(irq_state);
}
#endif // MICROPY_PY_THREAD

24
stmhal/pybthread.h
View File

@ -33,15 +33,23 @@ typedef struct _pyb_thread_t {
void *arg; // thread Python args, a GC root pointer
void *stack; // pointer to the stack
size_t stack_len; // number of words in the stack
struct _pyb_thread_t *prev;
struct _pyb_thread_t *next;
uint32_t timeslice;
struct _pyb_thread_t *all_next;
struct _pyb_thread_t *run_prev;
struct _pyb_thread_t *run_next;
struct _pyb_thread_t *queue_next;
} pyb_thread_t;
extern int pyb_thread_enabled;
extern pyb_thread_t *pyb_thread_cur;
typedef pyb_thread_t *pyb_mutex_t;
extern volatile int pyb_thread_enabled;
extern pyb_thread_t *volatile pyb_thread_all;
extern pyb_thread_t *volatile pyb_thread_cur;
void pyb_thread_init(pyb_thread_t *th);
void pyb_thread_deinit();
uint32_t pyb_thread_new(pyb_thread_t *th, void *stack, size_t stack_len, void *entry, void *arg);
void pyb_thread_dump(void);
static inline uint32_t pyb_thread_get_id(void) {
return (uint32_t)pyb_thread_cur;
@ -56,7 +64,15 @@ static inline void *pyb_thread_get_local(void) {
}
static inline void pyb_thread_yield(void) {
if (pyb_thread_cur->run_next == pyb_thread_cur) {
__WFI();
} else {
SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
}
}
void pyb_mutex_init(pyb_mutex_t *m);
int pyb_mutex_lock(pyb_mutex_t *m, int wait);
void pyb_mutex_unlock(pyb_mutex_t *m);
#endif // MICROPY_INCLUDED_STMHAL_PYBTHREAD_H

10
stmhal/stm32_it.c
View File

@ -70,6 +70,7 @@
#include "stm32_it.h"
#include STM32_HAL_H
#include "py/mpstate.h"
#include "py/obj.h"
#include "py/mphal.h"
#include "pendsv.h"
@ -315,10 +316,15 @@ void SysTick_Handler(void) {
}
#if MICROPY_PY_THREAD
// signal a thread switch at 4ms=250Hz
if (pyb_thread_enabled && (uwTick & 0x03) == 0x03) {
if (pyb_thread_enabled) {
if (pyb_thread_cur->timeslice == 0) {
if (pyb_thread_cur->run_next != pyb_thread_cur) {
SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
}
} else {
--pyb_thread_cur->timeslice;
}
}
#endif
}

10
stmhal/systick.c
View File

@ -29,9 +29,11 @@
#include "py/obj.h"
#include "irq.h"
#include "systick.h"
#include "pybthread.h"
// We provide our own version of HAL_Delay that calls __WFI while waiting, in
// order to reduce power consumption.
// Note: Upon entering this function we may or may not have the GIL.
void HAL_Delay(uint32_t Delay) {
if (query_irq() == IRQ_STATE_ENABLED) {
// IRQs enabled, so can use systick counter to do the delay
@ -40,8 +42,16 @@ void HAL_Delay(uint32_t Delay) {
// Wraparound of tick is taken care of by 2's complement arithmetic.
while (uwTick - start < Delay) {
// Enter sleep mode, waiting for (at least) the SysTick interrupt.
#if MICROPY_PY_THREAD
if (pyb_thread_enabled) {
pyb_thread_yield();
} else {
__WFI();
}
#else
__WFI();
#endif
}
} else {
// IRQs disabled, so need to use a busy loop for the delay.
// To prevent possible overflow of the counter we use a double loop.