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9b36cb4a41
While running a task, we may try to delete and free a task that is about to be run, because it's part of the local tasks list, or because rq_next points to it. So flag any task that is in the local tasks list to be deleted, instead of run, by setting t->process to NULL, and re-make rq_next a global, thread-local variable, that is modified if we attempt to delete that task. Many thanks to PiBa-NL for reporting this and analysing the problem. This should be backported to 1.8.
383 lines
11 KiB
C
383 lines
11 KiB
C
/*
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* Task management functions.
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*
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* Copyright 2000-2009 Willy Tarreau <w@1wt.eu>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*/
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#include <string.h>
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#include <common/config.h>
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#include <common/memory.h>
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#include <common/mini-clist.h>
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#include <common/standard.h>
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#include <common/time.h>
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#include <eb32sctree.h>
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#include <eb32tree.h>
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#include <proto/proxy.h>
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#include <proto/stream.h>
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#include <proto/task.h>
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struct pool_head *pool_head_task;
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/* This is the memory pool containing all the signal structs. These
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* struct are used to store each requiered signal between two tasks.
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*/
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struct pool_head *pool_head_notification;
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unsigned int nb_tasks = 0;
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unsigned long active_tasks_mask = 0; /* Mask of threads with active tasks */
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unsigned int tasks_run_queue = 0;
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unsigned int tasks_run_queue_cur = 0; /* copy of the run queue size */
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unsigned int nb_tasks_cur = 0; /* copy of the tasks count */
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unsigned int niced_tasks = 0; /* number of niced tasks in the run queue */
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THREAD_LOCAL struct task *curr_task = NULL; /* task currently running or NULL */
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THREAD_LOCAL struct eb32sc_node *rq_next = NULL; /* Next task to be potentially run */
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__decl_hathreads(HA_SPINLOCK_T __attribute__((aligned(64))) rq_lock); /* spin lock related to run queue */
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__decl_hathreads(HA_SPINLOCK_T __attribute__((aligned(64))) wq_lock); /* spin lock related to wait queue */
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static struct eb_root timers; /* sorted timers tree */
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static struct eb_root rqueue; /* tree constituting the run queue */
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static unsigned int rqueue_ticks; /* insertion count */
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/* Puts the task <t> in run queue at a position depending on t->nice. <t> is
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* returned. The nice value assigns boosts in 32th of the run queue size. A
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* nice value of -1024 sets the task to -tasks_run_queue*32, while a nice value
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* of 1024 sets the task to tasks_run_queue*32. The state flags are cleared, so
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* the caller will have to set its flags after this call.
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* The task must not already be in the run queue. If unsure, use the safer
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* task_wakeup() function.
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*/
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struct task *__task_wakeup(struct task *t)
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{
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tasks_run_queue++;
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active_tasks_mask |= t->thread_mask;
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t->rq.key = ++rqueue_ticks;
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if (likely(t->nice)) {
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int offset;
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niced_tasks++;
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if (likely(t->nice > 0))
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offset = (unsigned)((tasks_run_queue * (unsigned int)t->nice) / 32U);
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else
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offset = -(unsigned)((tasks_run_queue * (unsigned int)-t->nice) / 32U);
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t->rq.key += offset;
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}
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/* reset flag to pending ones
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* Note: __task_wakeup must not be called
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* if task is running
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*/
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t->state = t->pending_state;
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eb32sc_insert(&rqueue, &t->rq, t->thread_mask);
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return t;
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}
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/*
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* __task_queue()
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*
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* Inserts a task into the wait queue at the position given by its expiration
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* date. It does not matter if the task was already in the wait queue or not,
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* as it will be unlinked. The task must not have an infinite expiration timer.
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* Last, tasks must not be queued further than the end of the tree, which is
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* between <now_ms> and <now_ms> + 2^31 ms (now+24days in 32bit).
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*
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* This function should not be used directly, it is meant to be called by the
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* inline version of task_queue() which performs a few cheap preliminary tests
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* before deciding to call __task_queue().
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*/
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void __task_queue(struct task *task)
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{
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if (likely(task_in_wq(task)))
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__task_unlink_wq(task);
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/* the task is not in the queue now */
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task->wq.key = task->expire;
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#ifdef DEBUG_CHECK_INVALID_EXPIRATION_DATES
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if (tick_is_lt(task->wq.key, now_ms))
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/* we're queuing too far away or in the past (most likely) */
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return;
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#endif
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eb32_insert(&timers, &task->wq);
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return;
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}
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/*
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* Extract all expired timers from the timer queue, and wakes up all
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* associated tasks. Returns the date of next event (or eternity).
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*/
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int wake_expired_tasks()
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{
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struct task *task;
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struct eb32_node *eb;
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int ret = TICK_ETERNITY;
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while (1) {
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HA_SPIN_LOCK(TASK_WQ_LOCK, &wq_lock);
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lookup_next:
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eb = eb32_lookup_ge(&timers, now_ms - TIMER_LOOK_BACK);
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if (!eb) {
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/* we might have reached the end of the tree, typically because
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* <now_ms> is in the first half and we're first scanning the last
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* half. Let's loop back to the beginning of the tree now.
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*/
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eb = eb32_first(&timers);
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if (likely(!eb))
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break;
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}
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if (tick_is_lt(now_ms, eb->key)) {
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/* timer not expired yet, revisit it later */
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ret = eb->key;
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break;
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}
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/* timer looks expired, detach it from the queue */
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task = eb32_entry(eb, struct task, wq);
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__task_unlink_wq(task);
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/* It is possible that this task was left at an earlier place in the
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* tree because a recent call to task_queue() has not moved it. This
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* happens when the new expiration date is later than the old one.
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* Since it is very unlikely that we reach a timeout anyway, it's a
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* lot cheaper to proceed like this because we almost never update
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* the tree. We may also find disabled expiration dates there. Since
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* we have detached the task from the tree, we simply call task_queue
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* to take care of this. Note that we might occasionally requeue it at
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* the same place, before <eb>, so we have to check if this happens,
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* and adjust <eb>, otherwise we may skip it which is not what we want.
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* We may also not requeue the task (and not point eb at it) if its
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* expiration time is not set.
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*/
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if (!tick_is_expired(task->expire, now_ms)) {
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if (tick_isset(task->expire))
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__task_queue(task);
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goto lookup_next;
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}
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task_wakeup(task, TASK_WOKEN_TIMER);
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HA_SPIN_UNLOCK(TASK_WQ_LOCK, &wq_lock);
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}
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HA_SPIN_UNLOCK(TASK_WQ_LOCK, &wq_lock);
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return ret;
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}
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/* The run queue is chronologically sorted in a tree. An insertion counter is
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* used to assign a position to each task. This counter may be combined with
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* other variables (eg: nice value) to set the final position in the tree. The
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* counter may wrap without a problem, of course. We then limit the number of
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* tasks processed to 200 in any case, so that general latency remains low and
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* so that task positions have a chance to be considered.
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*
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* The function adjusts <next> if a new event is closer.
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*/
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void process_runnable_tasks()
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{
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struct task *t;
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int i;
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int max_processed;
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struct task *local_tasks[16];
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int local_tasks_count;
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int final_tasks_count;
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tasks_run_queue_cur = tasks_run_queue; /* keep a copy for reporting */
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nb_tasks_cur = nb_tasks;
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max_processed = 200;
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if (unlikely(global.nbthread <= 1)) {
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/* when no lock is needed, this loop is much faster */
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if (!(active_tasks_mask & tid_bit)) {
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activity[tid].empty_rq++;
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return;
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}
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active_tasks_mask &= ~tid_bit;
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rq_next = eb32sc_lookup_ge(&rqueue, rqueue_ticks - TIMER_LOOK_BACK, tid_bit);
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while (1) {
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if (!rq_next) {
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/* we might have reached the end of the tree, typically because
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* <rqueue_ticks> is in the first half and we're first scanning
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* the last half. Let's loop back to the beginning of the tree now.
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*/
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rq_next = eb32sc_first(&rqueue, tid_bit);
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if (!rq_next)
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break;
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}
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t = eb32sc_entry(rq_next, struct task, rq);
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rq_next = eb32sc_next(rq_next, tid_bit);
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__task_unlink_rq(t);
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t->state |= TASK_RUNNING;
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t->pending_state = 0;
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t->calls++;
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curr_task = t;
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/* This is an optimisation to help the processor's branch
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* predictor take this most common call.
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*/
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if (likely(t->process == process_stream))
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t = process_stream(t);
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else {
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if (t->process != NULL)
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t = t->process(t);
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else {
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__task_free(t);
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t = NULL;
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}
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}
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curr_task = NULL;
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if (likely(t != NULL)) {
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t->state &= ~TASK_RUNNING;
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/* If there is a pending state
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* we have to wake up the task
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* immediatly, else we defer
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* it into wait queue
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*/
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if (t->pending_state)
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__task_wakeup(t);
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else
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task_queue(t);
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}
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max_processed--;
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if (max_processed <= 0) {
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active_tasks_mask |= tid_bit;
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activity[tid].long_rq++;
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break;
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}
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}
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return;
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}
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HA_SPIN_LOCK(TASK_RQ_LOCK, &rq_lock);
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if (!(active_tasks_mask & tid_bit)) {
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HA_SPIN_UNLOCK(TASK_RQ_LOCK, &rq_lock);
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activity[tid].empty_rq++;
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return;
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}
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active_tasks_mask &= ~tid_bit;
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while (1) {
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/* Note: this loop is one of the fastest code path in
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* the whole program. It should not be re-arranged
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* without a good reason.
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*/
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/* we have to restart looking up after every batch */
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rq_next = eb32sc_lookup_ge(&rqueue, rqueue_ticks - TIMER_LOOK_BACK, tid_bit);
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for (local_tasks_count = 0; local_tasks_count < 16; local_tasks_count++) {
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if (unlikely(!rq_next)) {
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/* either we just started or we reached the end
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* of the tree, typically because <rqueue_ticks>
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* is in the first half and we're first scanning
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* the last half. Let's loop back to the beginning
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* of the tree now.
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*/
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rq_next = eb32sc_first(&rqueue, tid_bit);
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if (!rq_next)
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break;
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}
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t = eb32sc_entry(rq_next, struct task, rq);
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rq_next = eb32sc_next(rq_next, tid_bit);
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/* detach the task from the queue */
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__task_unlink_rq(t);
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local_tasks[local_tasks_count] = t;
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t->state |= TASK_RUNNING;
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t->pending_state = 0;
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t->calls++;
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max_processed--;
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}
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if (!local_tasks_count)
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break;
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HA_SPIN_UNLOCK(TASK_RQ_LOCK, &rq_lock);
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final_tasks_count = 0;
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for (i = 0; i < local_tasks_count ; i++) {
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t = local_tasks[i];
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/* This is an optimisation to help the processor's branch
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* predictor take this most common call.
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*/
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curr_task = t;
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if (likely(t->process == process_stream))
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t = process_stream(t);
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else {
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if (t->process != NULL)
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t = t->process(t);
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else {
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__task_free(t);
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t = NULL;
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}
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}
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curr_task = NULL;
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if (t)
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local_tasks[final_tasks_count++] = t;
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}
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for (i = 0; i < final_tasks_count ; i++) {
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t = local_tasks[i];
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/* If there is a pending state
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* we have to wake up the task
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* immediatly, else we defer
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* it into wait queue
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*/
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HA_SPIN_LOCK(TASK_RQ_LOCK, &rq_lock);
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t->state &= ~TASK_RUNNING;
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if (t->pending_state) {
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__task_wakeup(t);
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HA_SPIN_UNLOCK(TASK_RQ_LOCK, &rq_lock);
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}
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else {
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/* we must never hold the RQ lock before the WQ lock */
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HA_SPIN_UNLOCK(TASK_RQ_LOCK, &rq_lock);
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task_queue(t);
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}
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}
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HA_SPIN_LOCK(TASK_RQ_LOCK, &rq_lock);
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if (max_processed <= 0) {
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active_tasks_mask |= tid_bit;
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activity[tid].long_rq++;
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break;
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}
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}
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HA_SPIN_UNLOCK(TASK_RQ_LOCK, &rq_lock);
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}
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/* perform minimal intializations, report 0 in case of error, 1 if OK. */
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int init_task()
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{
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memset(&timers, 0, sizeof(timers));
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memset(&rqueue, 0, sizeof(rqueue));
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HA_SPIN_INIT(&wq_lock);
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HA_SPIN_INIT(&rq_lock);
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pool_head_task = create_pool("task", sizeof(struct task), MEM_F_SHARED);
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if (!pool_head_task)
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return 0;
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pool_head_notification = create_pool("notification", sizeof(struct notification), MEM_F_SHARED);
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if (!pool_head_notification)
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return 0;
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return 1;
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}
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/*
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* Local variables:
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* c-indent-level: 8
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* c-basic-offset: 8
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* End:
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*/
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