/***********************************************************************/ /* */ /* Objective Caml */ /* */ /* Xavier Leroy and Damien Doligez, INRIA Rocquencourt */ /* */ /* Copyright 1995 Institut National de Recherche en Informatique et */ /* Automatique. Distributed only by permission. */ /* */ /***********************************************************************/ /* $Id$ */ /* Thread interface for POSIX 1003.1c threads */ #include #include #include #include #include #include "alloc.h" #include "callback.h" #include "fail.h" #include "io.h" #include "memory.h" #include "misc.h" #include "mlvalues.h" #include "roots.h" #include "signals.h" #ifdef NATIVE_CODE #include "stack.h" #else #include "stacks.h" #endif #include "sys.h" /* Initial size of stack when a thread is created (4 Ko) */ #define Thread_stack_size (Stack_size / 4) /* Max computation time before rescheduling, in microseconds (50ms) */ #define Thread_timeout 50000 /* The ML value describing a thread (heap-allocated) */ struct caml_thread_descr { value ident; /* Unique integer ID */ value start_closure; /* The closure to start this thread */ value terminated; /* Mutex held while the thread is running */ }; #define Ident(v) (((struct caml_thread_descr *)(v))->ident) #define Start_closure(v) (((struct caml_thread_descr *)(v))->start_closure) #define Terminated(v) (((struct caml_thread_descr *)(v))->terminated) /* The infos on threads (allocated via malloc()) */ struct caml_thread_struct { pthread_t pthread; /* The Posix thread id */ value descr; /* The heap-allocated descriptor */ struct caml_thread_struct * next; /* Double linking of running threads */ struct caml_thread_struct * prev; #ifdef NATIVE_CODE char * bottom_of_stack; /* Saved value of caml_bottom_of_stack */ unsigned long last_retaddr; /* Saved value of caml_last_return_address */ value * gc_regs; /* Saved value of caml_gc_regs */ char * exception_pointer; /* Saved value of caml_exception_pointer */ struct caml__roots_block * local_roots; /* Saved value of local_roots */ #else value * stack_low; /* The execution stack for this thread */ value * stack_high; value * stack_threshold; value * sp; /* Saved value of extern_sp for this thread */ value * trapsp; /* Saved value of trapsp for this thread */ struct caml__roots_block * local_roots; /* Saved value of local_roots */ struct longjmp_buffer * external_raise; /* Saved external_raise */ #endif }; typedef struct caml_thread_struct * caml_thread_t; /* The descriptor for the currently executing thread */ static caml_thread_t curr_thread = NULL; /* The global mutex used to ensure that at most one thread is running Caml code */ static pthread_mutex_t caml_mutex; /* The key used for storing the thread descriptor in the specific data of the corresponding Posix thread. */ static pthread_key_t thread_descriptor_key; /* The key used for unlocking I/O channels on exceptions */ static pthread_key_t last_channel_locked_key; /* Identifier for next thread creation */ static long thread_next_ident = 0; /* Forward declarations */ value caml_mutex_new (value); value caml_mutex_lock (value); value caml_mutex_unlock (value); static void caml_pthread_check (int, char *); /* Hook for scanning the stacks of the other threads */ static void (*prev_scan_roots_hook) (scanning_action); static void caml_thread_scan_roots(scanning_action action) { caml_thread_t th; th = curr_thread; do { (*action)(th->descr, &th->descr); /* Don't rescan the stack of the current thread, it was done already */ if (th != curr_thread) { #ifdef NATIVE_CODE if (th->bottom_of_stack != NULL) do_local_roots(action, th->bottom_of_stack, th->last_retaddr, th->gc_regs, th->local_roots); #else do_local_roots(action, th->sp, th->stack_high, th->local_roots); #endif } th = th->next; } while (th != curr_thread); /* Hook */ if (prev_scan_roots_hook != NULL) (*prev_scan_roots_hook)(action); } /* Hooks for enter_blocking_section and leave_blocking_section */ static void (*prev_enter_blocking_section_hook) () = NULL; static void (*prev_leave_blocking_section_hook) () = NULL; static void caml_thread_enter_blocking_section(void) { if (prev_enter_blocking_section_hook != NULL) (*prev_enter_blocking_section_hook)(); /* Save the stack-related global variables in the thread descriptor of the current thread */ #ifdef NATIVE_CODE curr_thread->bottom_of_stack = caml_bottom_of_stack; curr_thread->last_retaddr = caml_last_return_address; curr_thread->gc_regs = caml_gc_regs; curr_thread->exception_pointer = caml_exception_pointer; curr_thread->local_roots = local_roots; #else curr_thread->stack_low = stack_low; curr_thread->stack_high = stack_high; curr_thread->stack_threshold = stack_threshold; curr_thread->sp = extern_sp; curr_thread->trapsp = trapsp; curr_thread->local_roots = local_roots; curr_thread->external_raise = external_raise; #endif /* Release the global mutex */ pthread_mutex_unlock(&caml_mutex); } static void caml_thread_leave_blocking_section(void) { /* Re-acquire the global mutex */ pthread_mutex_lock(&caml_mutex); /* Update curr_thread to point to the thread descriptor corresponding to the thread currently executing */ curr_thread = pthread_getspecific(thread_descriptor_key); /* Restore the stack-related global variables */ #ifdef NATIVE_CODE caml_bottom_of_stack= curr_thread->bottom_of_stack; caml_last_return_address = curr_thread->last_retaddr; caml_gc_regs = curr_thread->gc_regs; caml_exception_pointer = curr_thread->exception_pointer; local_roots = curr_thread->local_roots; #else stack_low = curr_thread->stack_low; stack_high = curr_thread->stack_high; stack_threshold = curr_thread->stack_threshold; extern_sp = curr_thread->sp; trapsp = curr_thread->trapsp; local_roots = curr_thread->local_roots; external_raise = curr_thread->external_raise; #endif if (prev_leave_blocking_section_hook != NULL) (*prev_leave_blocking_section_hook)(); } /* Hooks for I/O locking */ static void caml_io_mutex_free(struct channel *chan) { pthread_mutex_t * mutex = chan->mutex; if (mutex != NULL) { pthread_mutex_destroy(mutex); stat_free((char *) mutex); } } static void caml_io_mutex_lock(struct channel *chan) { if (chan->mutex == NULL) { pthread_mutex_t * mutex = (pthread_mutex_t *) stat_alloc(sizeof(pthread_mutex_t)); pthread_mutex_init(mutex, NULL); chan->mutex = (void *) mutex; } enter_blocking_section(); pthread_mutex_lock(chan->mutex); leave_blocking_section(); pthread_setspecific(last_channel_locked_key, (void *) chan); } static void caml_io_mutex_unlock(struct channel *chan) { pthread_mutex_unlock(chan->mutex); pthread_setspecific(last_channel_locked_key, NULL); } static void caml_io_mutex_unlock_exn(void) { struct channel * chan = pthread_getspecific(last_channel_locked_key); if (chan != NULL) caml_io_mutex_unlock(chan); } /* The "tick" thread fakes a SIGVTALRM signal at regular intervals. */ static void * caml_thread_tick(void * arg) { struct timeval timeout; while(1) { /* select() seems to be the most efficient way to suspend the thread for sub-second intervals */ timeout.tv_sec = 0; timeout.tv_usec = Thread_timeout; select(0, NULL, NULL, NULL, &timeout); /* This signal should never cause a callback, so don't go through handle_signal(), tweak the global variables directly. */ pending_signal = SIGVTALRM; #ifdef NATIVE_CODE young_limit = young_end; #else something_to_do = 1; #endif } return NULL; /* prevents compiler warning */ } /* Initialize the thread machinery */ value caml_thread_initialize(value unit) /* ML */ { pthread_t tick_pthread; pthread_attr_t attr; value mu = Val_unit; value descr; Begin_root (mu); /* Initialize the main mutex */ caml_pthread_check(pthread_mutex_init(&caml_mutex, NULL), "Thread.init"); pthread_mutex_lock(&caml_mutex); /* Initialize the keys */ pthread_key_create(&thread_descriptor_key, NULL); pthread_key_create(&last_channel_locked_key, NULL); /* Create and acquire a termination lock for the current thread */ mu = caml_mutex_new(Val_unit); caml_mutex_lock(mu); /* Create a descriptor for the current thread */ descr = alloc_tuple(3); Ident(descr) = Val_long(thread_next_ident); Start_closure(descr) = Val_unit; Terminated(descr) = mu; thread_next_ident++; /* Create an info block for the current thread */ curr_thread = (caml_thread_t) stat_alloc(sizeof(struct caml_thread_struct)); curr_thread->pthread = pthread_self(); curr_thread->descr = descr; curr_thread->next = curr_thread; curr_thread->prev = curr_thread; /* The stack-related fields will be filled in at the next enter_blocking_section */ /* Associate the thread descriptor with the thread */ pthread_setspecific(thread_descriptor_key, (void *) curr_thread); /* Set up the hooks */ prev_scan_roots_hook = scan_roots_hook; scan_roots_hook = caml_thread_scan_roots; prev_enter_blocking_section_hook = enter_blocking_section_hook; enter_blocking_section_hook = caml_thread_enter_blocking_section; prev_leave_blocking_section_hook = leave_blocking_section_hook; leave_blocking_section_hook = caml_thread_leave_blocking_section; channel_mutex_free = caml_io_mutex_free; channel_mutex_lock = caml_io_mutex_lock; channel_mutex_unlock = caml_io_mutex_unlock; channel_mutex_unlock_exn = caml_io_mutex_unlock_exn; /* Fork the tick thread */ pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); caml_pthread_check( pthread_create(&tick_pthread, &attr, caml_thread_tick, NULL), "Thread.init"); pthread_detach(tick_pthread); End_roots(); return Val_unit; } /* Create a thread */ static void * caml_thread_start(void * arg) { caml_thread_t th = (caml_thread_t) arg; value clos; /* Associate the thread descriptor with the thread */ pthread_setspecific(thread_descriptor_key, (void *) th); /* Acquire the global mutex and set up the stack variables */ leave_blocking_section(); /* Callback the closure */ clos = Start_closure(th->descr); Modify(&(Start_closure(th->descr)), Val_unit); callback(clos, Val_unit); /* Signal that the thread has terminated */ caml_mutex_unlock(Terminated(th->descr)); /* Remove th from the doubly-linked list of threads */ th->next->prev = th->prev; th->prev->next = th->next; #ifndef NATIVE_CODE /* Free the memory resources */ stat_free(th->stack_low); #endif /* Free the thread descriptor */ stat_free(th); /* Release the main mutex (forever) */ enter_blocking_section(); /* The thread now stops running */ return NULL; } value caml_thread_new(value clos) /* ML */ { pthread_attr_t attr; caml_thread_t th; value mu = Val_unit; value descr; int err; Begin_roots2 (clos, mu) /* Create and acquire the termination lock */ mu = caml_mutex_new(Val_unit); caml_mutex_lock(mu); /* Create a descriptor for the new thread */ descr = alloc_tuple(3); Ident(descr) = Val_long(thread_next_ident); Start_closure(descr) = clos; Terminated(descr) = mu; thread_next_ident++; /* Create an info block for the current thread */ th = (caml_thread_t) stat_alloc(sizeof(struct caml_thread_struct)); th->descr = descr; #ifdef NATIVE_CODE th->bottom_of_stack = NULL; th->exception_pointer = NULL; th->local_roots = NULL; #else /* Allocate the stacks */ th->stack_low = (value *) stat_alloc(Thread_stack_size); th->stack_high = th->stack_low + Thread_stack_size / sizeof(value); th->stack_threshold = th->stack_low + Stack_threshold / sizeof(value); th->sp = th->stack_high; th->trapsp = th->stack_high; th->local_roots = NULL; th->external_raise = NULL; #endif /* Add thread info block to the list of threads */ th->next = curr_thread->next; th->prev = curr_thread; curr_thread->next->prev = th; curr_thread->next = th; /* Fork the new thread */ pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); err = pthread_create(&th->pthread, &attr, caml_thread_start, (void *) th); if (err != 0) { /* Fork failed, remove thread info block from list of threads */ th->next->prev = curr_thread; curr_thread->next = th->next; #ifndef NATIVE_CODE stat_free(th->stack_low); #endif stat_free(th); caml_pthread_check(err, "Thread.create"); } End_roots(); return descr; } /* Return the current thread */ value caml_thread_self(value unit) /* ML */ { if (curr_thread == NULL) invalid_argument("Thread.self: not initialized"); return curr_thread->descr; } /* Return the identifier of a thread */ value caml_thread_id(value th) /* ML */ { return Ident(th); } /* Allow re-scheduling */ value caml_thread_yield(value unit) /* ML */ { enter_blocking_section(); sched_yield(); leave_blocking_section(); return Val_unit; } /* Suspend the current thread until another thread terminates */ value caml_thread_join(value th) /* ML */ { value mut = Terminated(th); Begin_root(mut) caml_mutex_lock(mut); caml_mutex_unlock(mut); End_roots(); return Val_unit; } /* Mutex operations */ #define Mutex_val(v) ((pthread_mutex_t *) Field(v, 1)) #define Max_mutex_number 1000 static void caml_mutex_finalize(value wrapper) { pthread_mutex_t * mut = Mutex_val(wrapper); pthread_mutex_destroy(mut); stat_free(mut); } value caml_mutex_new(value unit) /* ML */ { pthread_mutex_t * mut; value wrapper; mut = stat_alloc(sizeof(pthread_mutex_t)); caml_pthread_check(pthread_mutex_init(mut, NULL), "Mutex.create"); wrapper = alloc_final(2, caml_mutex_finalize, 1, Max_mutex_number); Mutex_val(wrapper) = mut; return wrapper; } value caml_mutex_lock(value wrapper) /* ML */ { int retcode; pthread_mutex_t * mut = Mutex_val(wrapper); enter_blocking_section(); retcode = pthread_mutex_lock(mut); leave_blocking_section(); caml_pthread_check(retcode, "Mutex.lock"); return Val_unit; } value caml_mutex_unlock(value wrapper) /* ML */ { int retcode; pthread_mutex_t * mut = Mutex_val(wrapper); enter_blocking_section(); retcode = pthread_mutex_unlock(mut); leave_blocking_section(); caml_pthread_check(retcode, "Mutex.unlock"); return Val_unit; } value caml_mutex_try_lock(value wrapper) /* ML */ { int retcode; pthread_mutex_t * mut = Mutex_val(wrapper); retcode = pthread_mutex_trylock(mut); if (retcode == EBUSY) return Val_false; caml_pthread_check(retcode, "Mutex.try_lock"); return Val_true; } /* Conditions operations */ #define Condition_val(v) ((pthread_cond_t *) Field(v, 1)) #define Max_condition_number 1000 static void caml_condition_finalize(value wrapper) { pthread_cond_t * cond = Condition_val(wrapper); pthread_cond_destroy(cond); stat_free(cond); } value caml_condition_new(value unit) /* ML */ { pthread_cond_t * cond; value wrapper; cond = stat_alloc(sizeof(pthread_cond_t)); caml_pthread_check(pthread_cond_init(cond, NULL), "Condition.create"); wrapper = alloc_final(2, caml_condition_finalize, 1, Max_condition_number); Condition_val(wrapper) = cond; return wrapper; } value caml_condition_wait(value wcond, value wmut) /* ML */ { int retcode; pthread_cond_t * cond = Condition_val(wcond); pthread_mutex_t * mut = Mutex_val(wmut); enter_blocking_section(); retcode = pthread_cond_wait(cond, mut); leave_blocking_section(); caml_pthread_check(retcode, "Condition.wait"); return Val_unit; } value caml_condition_signal(value wrapper) /* ML */ { int retcode; pthread_cond_t * cond = Condition_val(wrapper); enter_blocking_section(); retcode = pthread_cond_signal(cond); leave_blocking_section(); caml_pthread_check(retcode, "Condition.signal"); return Val_unit; } value caml_condition_broadcast(value wrapper) /* ML */ { int retcode; pthread_cond_t * cond = Condition_val(wrapper); enter_blocking_section(); retcode = pthread_cond_broadcast(cond); leave_blocking_section(); caml_pthread_check(retcode, "Condition.broadcast"); return Val_unit; } /* Error report */ static void caml_pthread_check(int retcode, char *msg) { char * err; int errlen, msglen; value str; if (retcode == 0) return; err = strerror(retcode); msglen = strlen(msg); errlen = strlen(err); str = alloc_string(msglen + 2 + errlen); bcopy(msg, &Byte(str, 0), msglen); bcopy(": ", &Byte(str, msglen), 2); bcopy(err, &Byte(str, msglen + 2), errlen); raise_sys_error(str); }