diff options
Diffstat (limited to 'sched.c')
| -rw-r--r-- | sched.c | 843 |
1 files changed, 843 insertions, 0 deletions
@@ -0,0 +1,843 @@ +/* + chronyd/chronyc - Programs for keeping computer clocks accurate. + + ********************************************************************** + * Copyright (C) Richard P. Curnow 1997-2003 + * Copyright (C) Miroslav Lichvar 2011, 2013-2016 + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of version 2 of the GNU General Public License as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * + ********************************************************************** + + ======================================================================= + + This file contains the scheduling loop and the timeout queue. + + */ + +#include "config.h" + +#include "sysincl.h" + +#include "array.h" +#include "sched.h" +#include "memory.h" +#include "util.h" +#include "local.h" +#include "logging.h" + +/* ================================================== */ + +/* Flag indicating that we are initialised */ +static int initialised = 0; + +/* ================================================== */ + +/* One more than the highest file descriptor that is registered */ +static unsigned int one_highest_fd; + +#ifndef FD_SETSIZE +/* If FD_SETSIZE is not defined, assume that fd_set is implemented + as a fixed size array of bits, possibly embedded inside a record */ +#define FD_SETSIZE (sizeof(fd_set) * 8) +#endif + +typedef struct { + SCH_FileHandler handler; + SCH_ArbitraryArgument arg; + int events; +} FileHandlerEntry; + +static ARR_Instance file_handlers; + +/* Timestamp when last select() returned */ +static struct timespec last_select_ts, last_select_ts_raw; +static double last_select_ts_err; + +#define TS_MONO_PRECISION_NS 10000000U + +/* Monotonic low-precision timestamp measuring interval since the start */ +static double last_select_ts_mono; +static uint32_t last_select_ts_mono_ns; + +/* ================================================== */ + +/* Variables to handler the timer queue */ + +typedef struct _TimerQueueEntry +{ + struct _TimerQueueEntry *next; /* Forward and back links in the list */ + struct _TimerQueueEntry *prev; + struct timespec ts; /* Local system time at which the + timeout is to expire. Clearly this + must be in terms of what the + operating system thinks of as + system time, because it will be an + argument to select(). Therefore, + any fudges etc that our local time + driver module would apply to time + that we pass to clients etc doesn't + apply to this. */ + SCH_TimeoutID id; /* ID to allow client to delete + timeout */ + SCH_TimeoutClass class; /* The class that the epoch is in */ + SCH_TimeoutHandler handler; /* The handler routine to use */ + SCH_ArbitraryArgument arg; /* The argument to pass to the handler */ + +} TimerQueueEntry; + +/* The timer queue. We only use the next and prev entries of this + record, these chain to the real entries. */ +static TimerQueueEntry timer_queue; +static unsigned long n_timer_queue_entries; +static SCH_TimeoutID next_tqe_id; + +/* Pointer to head of free list */ +static TimerQueueEntry *tqe_free_list = NULL; + +/* Timestamp when was last timeout dispatched for each class */ +static struct timespec last_class_dispatch[SCH_NumberOfClasses]; + +/* ================================================== */ + +static int need_to_exit; + +/* ================================================== */ + +static void +handle_slew(struct timespec *raw, + struct timespec *cooked, + double dfreq, + double doffset, + LCL_ChangeType change_type, + void *anything); + +/* ================================================== */ + +void +SCH_Initialise(void) +{ + file_handlers = ARR_CreateInstance(sizeof (FileHandlerEntry)); + + n_timer_queue_entries = 0; + next_tqe_id = 0; + + timer_queue.next = &timer_queue; + timer_queue.prev = &timer_queue; + + need_to_exit = 0; + + LCL_AddParameterChangeHandler(handle_slew, NULL); + + LCL_ReadRawTime(&last_select_ts_raw); + last_select_ts = last_select_ts_raw; + last_select_ts_mono = 0.0; + last_select_ts_mono_ns = 0; + + initialised = 1; +} + + +/* ================================================== */ + +void +SCH_Finalise(void) { + ARR_DestroyInstance(file_handlers); + + LCL_RemoveParameterChangeHandler(handle_slew, NULL); + + initialised = 0; +} + +/* ================================================== */ + +void +SCH_AddFileHandler +(int fd, int events, SCH_FileHandler handler, SCH_ArbitraryArgument arg) +{ + FileHandlerEntry *ptr; + + assert(initialised); + assert(events); + assert(fd >= 0); + + if (fd >= FD_SETSIZE) + LOG_FATAL("Too many file descriptors"); + + /* Resize the array if the descriptor is highest so far */ + while (ARR_GetSize(file_handlers) <= fd) { + ptr = ARR_GetNewElement(file_handlers); + ptr->handler = NULL; + ptr->arg = NULL; + ptr->events = 0; + } + + ptr = ARR_GetElement(file_handlers, fd); + + /* Don't want to allow the same fd to register a handler more than + once without deleting a previous association - this suggests + a bug somewhere else in the program. */ + assert(!ptr->handler); + + ptr->handler = handler; + ptr->arg = arg; + ptr->events = events; + + if (one_highest_fd < fd + 1) + one_highest_fd = fd + 1; +} + + +/* ================================================== */ + +void +SCH_RemoveFileHandler(int fd) +{ + FileHandlerEntry *ptr; + + assert(initialised); + + ptr = ARR_GetElement(file_handlers, fd); + + /* Check that a handler was registered for the fd in question */ + assert(ptr->handler); + + ptr->handler = NULL; + ptr->arg = NULL; + ptr->events = 0; + + /* Find new highest file descriptor */ + while (one_highest_fd > 0) { + ptr = ARR_GetElement(file_handlers, one_highest_fd - 1); + if (ptr->handler) + break; + one_highest_fd--; + } +} + +/* ================================================== */ + +void +SCH_SetFileHandlerEvent(int fd, int event, int enable) +{ + FileHandlerEntry *ptr; + + ptr = ARR_GetElement(file_handlers, fd); + + if (enable) + ptr->events |= event; + else + ptr->events &= ~event; +} + +/* ================================================== */ + +void +SCH_GetLastEventTime(struct timespec *cooked, double *err, struct timespec *raw) +{ + if (cooked) { + *cooked = last_select_ts; + if (err) + *err = last_select_ts_err; + } + if (raw) + *raw = last_select_ts_raw; +} + +/* ================================================== */ + +double +SCH_GetLastEventMonoTime(void) +{ + return last_select_ts_mono; +} + +/* ================================================== */ + +#define TQE_ALLOC_QUANTUM 32 + +static TimerQueueEntry * +allocate_tqe(void) +{ + TimerQueueEntry *new_block; + TimerQueueEntry *result; + int i; + if (tqe_free_list == NULL) { + new_block = MallocArray(TimerQueueEntry, TQE_ALLOC_QUANTUM); + for (i=1; i<TQE_ALLOC_QUANTUM; i++) { + new_block[i].next = &(new_block[i-1]); + } + new_block[0].next = NULL; + tqe_free_list = &(new_block[TQE_ALLOC_QUANTUM - 1]); + } + + result = tqe_free_list; + tqe_free_list = tqe_free_list->next; + return result; +} + +/* ================================================== */ + +static void +release_tqe(TimerQueueEntry *node) +{ + node->next = tqe_free_list; + tqe_free_list = node; +} + +/* ================================================== */ + +static SCH_TimeoutID +get_new_tqe_id(void) +{ + TimerQueueEntry *ptr; + +try_again: + next_tqe_id++; + if (!next_tqe_id) + goto try_again; + + /* Make sure the ID isn't already used */ + for (ptr = timer_queue.next; ptr != &timer_queue; ptr = ptr->next) + if (ptr->id == next_tqe_id) + goto try_again; + + return next_tqe_id; +} + +/* ================================================== */ + +SCH_TimeoutID +SCH_AddTimeout(struct timespec *ts, SCH_TimeoutHandler handler, SCH_ArbitraryArgument arg) +{ + TimerQueueEntry *new_tqe; + TimerQueueEntry *ptr; + + assert(initialised); + + new_tqe = allocate_tqe(); + + new_tqe->id = get_new_tqe_id(); + new_tqe->handler = handler; + new_tqe->arg = arg; + new_tqe->ts = *ts; + new_tqe->class = SCH_ReservedTimeoutValue; + + /* Now work out where to insert the new entry in the list */ + for (ptr = timer_queue.next; ptr != &timer_queue; ptr = ptr->next) { + if (UTI_CompareTimespecs(&new_tqe->ts, &ptr->ts) == -1) { + /* If the new entry comes before the current pointer location in + the list, we want to insert the new entry just before ptr. */ + break; + } + } + + /* At this stage, we want to insert the new entry immediately before + the entry identified by 'ptr' */ + + new_tqe->next = ptr; + new_tqe->prev = ptr->prev; + ptr->prev->next = new_tqe; + ptr->prev = new_tqe; + + n_timer_queue_entries++; + + return new_tqe->id; +} + +/* ================================================== */ +/* This queues a timeout to elapse at a given delta time relative to + the current (raw) time */ + +SCH_TimeoutID +SCH_AddTimeoutByDelay(double delay, SCH_TimeoutHandler handler, SCH_ArbitraryArgument arg) +{ + struct timespec now, then; + + assert(initialised); + assert(delay >= 0.0); + + LCL_ReadRawTime(&now); + UTI_AddDoubleToTimespec(&now, delay, &then); + if (UTI_CompareTimespecs(&now, &then) > 0) { + LOG_FATAL("Timeout overflow"); + } + + return SCH_AddTimeout(&then, handler, arg); + +} + +/* ================================================== */ + +SCH_TimeoutID +SCH_AddTimeoutInClass(double min_delay, double separation, double randomness, + SCH_TimeoutClass class, + SCH_TimeoutHandler handler, SCH_ArbitraryArgument arg) +{ + TimerQueueEntry *new_tqe; + TimerQueueEntry *ptr; + struct timespec now; + double diff, r; + double new_min_delay; + + assert(initialised); + assert(min_delay >= 0.0); + assert(class < SCH_NumberOfClasses); + + if (randomness > 0.0) { + uint32_t rnd; + + UTI_GetRandomBytes(&rnd, sizeof (rnd)); + r = rnd * (randomness / (uint32_t)-1) + 1.0; + min_delay *= r; + separation *= r; + } + + LCL_ReadRawTime(&now); + new_min_delay = min_delay; + + /* Check the separation from the last dispatched timeout */ + diff = UTI_DiffTimespecsToDouble(&now, &last_class_dispatch[class]); + if (diff < separation && diff >= 0.0 && diff + new_min_delay < separation) { + new_min_delay = separation - diff; + } + + /* Scan through list for entries in the same class and increase min_delay + if necessary to keep at least the separation away */ + for (ptr = timer_queue.next; ptr != &timer_queue; ptr = ptr->next) { + if (ptr->class == class) { + diff = UTI_DiffTimespecsToDouble(&ptr->ts, &now); + if (new_min_delay > diff) { + if (new_min_delay - diff < separation) { + new_min_delay = diff + separation; + } + } else { + if (diff - new_min_delay < separation) { + new_min_delay = diff + separation; + } + } + } + } + + for (ptr = timer_queue.next; ptr != &timer_queue; ptr = ptr->next) { + diff = UTI_DiffTimespecsToDouble(&ptr->ts, &now); + if (diff > new_min_delay) { + break; + } + } + + /* We have located the insertion point */ + new_tqe = allocate_tqe(); + + new_tqe->id = get_new_tqe_id(); + new_tqe->handler = handler; + new_tqe->arg = arg; + UTI_AddDoubleToTimespec(&now, new_min_delay, &new_tqe->ts); + new_tqe->class = class; + + new_tqe->next = ptr; + new_tqe->prev = ptr->prev; + ptr->prev->next = new_tqe; + ptr->prev = new_tqe; + n_timer_queue_entries++; + + return new_tqe->id; +} + +/* ================================================== */ + +void +SCH_RemoveTimeout(SCH_TimeoutID id) +{ + TimerQueueEntry *ptr; + + assert(initialised); + + if (!id) + return; + + for (ptr = timer_queue.next; ptr != &timer_queue; ptr = ptr->next) { + + if (ptr->id == id) { + /* Found the required entry */ + + /* Unlink from the queue */ + ptr->next->prev = ptr->prev; + ptr->prev->next = ptr->next; + + /* Decrement entry count */ + --n_timer_queue_entries; + + /* Release memory back to the operating system */ + release_tqe(ptr); + + return; + } + } + + /* Catch calls with invalid non-zero ID */ + assert(0); +} + +/* ================================================== */ +/* Try to dispatch any timeouts that have already gone by, and + keep going until all are done. (The earlier ones may take so + long to do that the later ones come around by the time they are + completed). */ + +static void +dispatch_timeouts(struct timespec *now) { + TimerQueueEntry *ptr; + SCH_TimeoutHandler handler; + SCH_ArbitraryArgument arg; + int n_done = 0, n_entries_on_start = n_timer_queue_entries; + + while (1) { + LCL_ReadRawTime(now); + + if (!(n_timer_queue_entries > 0 && + UTI_CompareTimespecs(now, &timer_queue.next->ts) >= 0)) { + break; + } + + ptr = timer_queue.next; + + last_class_dispatch[ptr->class] = *now; + + handler = ptr->handler; + arg = ptr->arg; + + SCH_RemoveTimeout(ptr->id); + + /* Dispatch the handler */ + (handler)(arg); + + /* Increment count of timeouts handled */ + ++n_done; + + /* If more timeouts were handled than there were in the timer queue on + start and there are now, assume some code is scheduling timeouts with + negative delays and abort. Make the actual limit higher in case the + machine is temporarily overloaded and dispatching the handlers takes + more time than was delay of a scheduled timeout. */ + if (n_done > n_timer_queue_entries * 4 && + n_done > n_entries_on_start * 4) { + LOG_FATAL("Possible infinite loop in scheduling"); + } + } +} + +/* ================================================== */ + +/* nfd is the number of bits set in all fd_sets */ + +static void +dispatch_filehandlers(int nfd, fd_set *read_fds, fd_set *write_fds, fd_set *except_fds) +{ + FileHandlerEntry *ptr; + int fd; + + for (fd = 0; nfd && fd < one_highest_fd; fd++) { + if (except_fds && FD_ISSET(fd, except_fds)) { + /* This descriptor has an exception, dispatch its handler */ + ptr = (FileHandlerEntry *)ARR_GetElement(file_handlers, fd); + if (ptr->handler) + (ptr->handler)(fd, SCH_FILE_EXCEPTION, ptr->arg); + nfd--; + + /* Don't try to read from it now */ + if (read_fds && FD_ISSET(fd, read_fds)) { + FD_CLR(fd, read_fds); + nfd--; + } + } + + if (read_fds && FD_ISSET(fd, read_fds)) { + /* This descriptor can be read from, dispatch its handler */ + ptr = (FileHandlerEntry *)ARR_GetElement(file_handlers, fd); + if (ptr->handler) + (ptr->handler)(fd, SCH_FILE_INPUT, ptr->arg); + nfd--; + } + + if (write_fds && FD_ISSET(fd, write_fds)) { + /* This descriptor can be written to, dispatch its handler */ + ptr = (FileHandlerEntry *)ARR_GetElement(file_handlers, fd); + if (ptr->handler) + (ptr->handler)(fd, SCH_FILE_OUTPUT, ptr->arg); + nfd--; + } + } +} + +/* ================================================== */ + +static void +handle_slew(struct timespec *raw, + struct timespec *cooked, + double dfreq, + double doffset, + LCL_ChangeType change_type, + void *anything) +{ + TimerQueueEntry *ptr; + double delta; + int i; + + if (change_type != LCL_ChangeAdjust) { + /* Make sure this handler is invoked first in order to not shift new timers + added from other handlers */ + assert(LCL_IsFirstParameterChangeHandler(handle_slew)); + + /* If a step change occurs, just shift all raw time stamps by the offset */ + + for (ptr = timer_queue.next; ptr != &timer_queue; ptr = ptr->next) { + UTI_AddDoubleToTimespec(&ptr->ts, -doffset, &ptr->ts); + } + + for (i = 0; i < SCH_NumberOfClasses; i++) { + UTI_AddDoubleToTimespec(&last_class_dispatch[i], -doffset, &last_class_dispatch[i]); + } + + UTI_AddDoubleToTimespec(&last_select_ts_raw, -doffset, &last_select_ts_raw); + } + + UTI_AdjustTimespec(&last_select_ts, cooked, &last_select_ts, &delta, dfreq, doffset); +} + +/* ================================================== */ + +static void +fill_fd_sets(fd_set **read_fds, fd_set **write_fds, fd_set **except_fds) +{ + FileHandlerEntry *handlers; + fd_set *rd, *wr, *ex; + int i, n, events; + + n = ARR_GetSize(file_handlers); + handlers = ARR_GetElements(file_handlers); + rd = wr = ex = NULL; + + for (i = 0; i < n; i++) { + events = handlers[i].events; + + if (!events) + continue; + + if (events & SCH_FILE_INPUT) { + if (!rd) { + rd = *read_fds; + FD_ZERO(rd); + } + FD_SET(i, rd); + } + + if (events & SCH_FILE_OUTPUT) { + if (!wr) { + wr = *write_fds; + FD_ZERO(wr); + } + FD_SET(i, wr); + } + + if (events & SCH_FILE_EXCEPTION) { + if (!ex) { + ex = *except_fds; + FD_ZERO(ex); + } + FD_SET(i, ex); + } + } + + if (!rd) + *read_fds = NULL; + if (!wr) + *write_fds = NULL; + if (!ex) + *except_fds = NULL; +} + +/* ================================================== */ + +#define JUMP_DETECT_THRESHOLD 10 + +static int +check_current_time(struct timespec *prev_raw, struct timespec *raw, int timeout, + struct timeval *orig_select_tv, + struct timeval *rem_select_tv) +{ + struct timespec elapsed_min, elapsed_max, orig_select_ts, rem_select_ts; + double step, elapsed; + + UTI_TimevalToTimespec(orig_select_tv, &orig_select_ts); + + /* Get an estimate of the time spent waiting in the select() call. On some + systems (e.g. Linux) the timeout timeval is modified to return the + remaining time, use that information. */ + if (timeout) { + elapsed_max = elapsed_min = orig_select_ts; + } else if (rem_select_tv && rem_select_tv->tv_sec >= 0 && + rem_select_tv->tv_sec <= orig_select_tv->tv_sec && + (rem_select_tv->tv_sec != orig_select_tv->tv_sec || + rem_select_tv->tv_usec != orig_select_tv->tv_usec)) { + UTI_TimevalToTimespec(rem_select_tv, &rem_select_ts); + UTI_DiffTimespecs(&elapsed_min, &orig_select_ts, &rem_select_ts); + elapsed_max = elapsed_min; + } else { + if (rem_select_tv) + elapsed_max = orig_select_ts; + else + UTI_DiffTimespecs(&elapsed_max, raw, prev_raw); + UTI_ZeroTimespec(&elapsed_min); + } + + if (last_select_ts_raw.tv_sec + elapsed_min.tv_sec > + raw->tv_sec + JUMP_DETECT_THRESHOLD) { + LOG(LOGS_WARN, "Backward time jump detected!"); + } else if (prev_raw->tv_sec + elapsed_max.tv_sec + JUMP_DETECT_THRESHOLD < + raw->tv_sec) { + LOG(LOGS_WARN, "Forward time jump detected!"); + } else { + return 1; + } + + step = UTI_DiffTimespecsToDouble(&last_select_ts_raw, raw); + elapsed = UTI_TimespecToDouble(&elapsed_min); + step += elapsed; + + /* Cooked time may no longer be valid after dispatching the handlers */ + LCL_NotifyExternalTimeStep(raw, raw, step, fabs(step)); + + return 0; +} + +/* ================================================== */ + +static void +update_monotonic_time(struct timespec *now, struct timespec *before) +{ + struct timespec diff; + + /* Avoid frequent floating-point operations and handle small + increments to a large value */ + + UTI_DiffTimespecs(&diff, now, before); + if (diff.tv_sec == 0) { + last_select_ts_mono_ns += diff.tv_nsec; + } else { + last_select_ts_mono += fabs(UTI_TimespecToDouble(&diff) + + last_select_ts_mono_ns / 1.0e9); + last_select_ts_mono_ns = 0; + } + + if (last_select_ts_mono_ns > TS_MONO_PRECISION_NS) { + last_select_ts_mono += last_select_ts_mono_ns / 1.0e9; + last_select_ts_mono_ns = 0; + } +} + +/* ================================================== */ + +void +SCH_MainLoop(void) +{ + fd_set read_fds, write_fds, except_fds; + fd_set *p_read_fds, *p_write_fds, *p_except_fds; + int status, errsv; + struct timeval tv, saved_tv, *ptv; + struct timespec ts, now, saved_now, cooked; + double err; + + assert(initialised); + + while (!need_to_exit) { + /* Dispatch timeouts and fill now with current raw time */ + dispatch_timeouts(&now); + saved_now = now; + + /* The timeout handlers may request quit */ + if (need_to_exit) + break; + + /* Check whether there is a timeout and set it up */ + if (n_timer_queue_entries > 0) { + UTI_DiffTimespecs(&ts, &timer_queue.next->ts, &now); + assert(ts.tv_sec > 0 || ts.tv_nsec > 0); + + UTI_TimespecToTimeval(&ts, &tv); + ptv = &tv; + saved_tv = tv; + } else { + ptv = NULL; + saved_tv.tv_sec = saved_tv.tv_usec = 0; + } + + p_read_fds = &read_fds; + p_write_fds = &write_fds; + p_except_fds = &except_fds; + fill_fd_sets(&p_read_fds, &p_write_fds, &p_except_fds); + + /* if there are no file descriptors being waited on and no + timeout set, this is clearly ridiculous, so stop the run */ + if (!ptv && !p_read_fds && !p_write_fds) + LOG_FATAL("Nothing to do"); + + status = select(one_highest_fd, p_read_fds, p_write_fds, p_except_fds, ptv); + errsv = errno; + + LCL_ReadRawTime(&now); + LCL_CookTime(&now, &cooked, &err); + + update_monotonic_time(&now, &last_select_ts_raw); + + /* Check if the time didn't jump unexpectedly */ + if (!check_current_time(&saved_now, &now, status == 0, &saved_tv, ptv)) { + /* Cook the time again after handling the step */ + LCL_CookTime(&now, &cooked, &err); + } + + last_select_ts_raw = now; + last_select_ts = cooked; + last_select_ts_err = err; + + if (status < 0) { + if (!need_to_exit && errsv != EINTR) { + LOG_FATAL("select() failed : %s", strerror(errsv)); + } + } else if (status > 0) { + /* A file descriptor is ready for input or output */ + dispatch_filehandlers(status, p_read_fds, p_write_fds, p_except_fds); + } else { + /* No descriptors readable, timeout must have elapsed. + Therefore, tv must be non-null */ + assert(ptv); + + /* There's nothing to do here, since the timeouts + will be dispatched at the top of the next loop + cycle */ + + } + } +} + +/* ================================================== */ + +void +SCH_QuitProgram(void) +{ + need_to_exit = 1; +} + +/* ================================================== */ + |