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13afcb7ab3
There's a very small but existing uncertainty window when waking another thread up where it is possible for task_wakeup() not to wake the other task up because it's still running while this once is in the process of finishing and loses its TASK_RUNNING flag. In this case the wakeup will be missed. The problem is that we have a single flag to store 3 states, since the transition from running to sleeping isn't atomic. Thus we need to have another flag to cover this part. This patch introduces TASK_QUEUED to mention that the task is already in the run queue, running or not. This bit will be removed while TASK_RUNNING is kept once dequeued, and will be used when removing TASK_RUNNING to check if the task has been requeued. It might be possible to slightly improve this but the occurrence rate is quite low and we don't really need to complexify the scheduler to optimize for a rare case. The impact with the current code is very low since we have few inter- thread wakeups. Most of them are caused by checks killing sessions. This must be backported to 1.9.
106 lines
4.2 KiB
C
106 lines
4.2 KiB
C
/*
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* include/types/task.h
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* Macros, variables and structures for task management.
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*
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* Copyright (C) 2000-2010 Willy Tarreau - w@1wt.eu
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _TYPES_TASK_H
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#define _TYPES_TASK_H
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#include <sys/time.h>
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#include <common/config.h>
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#include <common/mini-clist.h>
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#include <eb32sctree.h>
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#include <eb32tree.h>
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/* values for task->state */
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#define TASK_SLEEPING 0x0000 /* task sleeping */
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#define TASK_RUNNING 0x0001 /* the task is currently running */
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#define TASK_GLOBAL 0x0002 /* The task is currently in the global runqueue */
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#define TASK_QUEUED 0x0004 /* The task has been (re-)added to the run queue */
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#define TASK_WOKEN_INIT 0x0100 /* woken up for initialisation purposes */
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#define TASK_WOKEN_TIMER 0x0200 /* woken up because of expired timer */
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#define TASK_WOKEN_IO 0x0400 /* woken up because of completed I/O */
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#define TASK_WOKEN_SIGNAL 0x0800 /* woken up by a system signal */
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#define TASK_WOKEN_MSG 0x1000 /* woken up by another task's message */
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#define TASK_WOKEN_RES 0x2000 /* woken up because of available resource */
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#define TASK_WOKEN_OTHER 0x4000 /* woken up for an unspecified reason */
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/* use this to check a task state or to clean it up before queueing */
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#define TASK_WOKEN_ANY (TASK_WOKEN_OTHER|TASK_WOKEN_INIT|TASK_WOKEN_TIMER| \
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TASK_WOKEN_IO|TASK_WOKEN_SIGNAL|TASK_WOKEN_MSG| \
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TASK_WOKEN_RES)
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struct notification {
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struct list purge_me; /* Part of the list of signals to be purged in the
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case of the LUA execution stack crash. */
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struct list wake_me; /* Part of list of signals to be targeted if an
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event occurs. */
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struct task *task; /* The task to be wake if an event occurs. */
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__decl_hathreads(HA_SPINLOCK_T lock);
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};
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/* This part is common between struct task and struct tasklet so that tasks
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* can be used as-is as tasklets.
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*/
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#define TASK_COMMON \
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struct { \
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unsigned short state; /* task state : bitfield of TASK_ */ \
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short nice; /* task prio from -1024 to +1024, or -32768 for tasklets */ \
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unsigned int calls; /* number of times process was called */ \
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uint64_t cpu_time; /* total CPU time consumed */ \
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struct task *(*process)(struct task *t, void *ctx, unsigned short state); /* the function which processes the task */ \
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void *context; /* the task's context */ \
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}
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/* The base for all tasks */
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struct task {
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TASK_COMMON; /* must be at the beginning! */
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struct eb32sc_node rq; /* ebtree node used to hold the task in the run queue */
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struct eb32_node wq; /* ebtree node used to hold the task in the wait queue */
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int expire; /* next expiration date for this task, in ticks */
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unsigned long thread_mask; /* mask of thread IDs authorized to process the task */
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uint64_t call_date; /* date of the last task wakeup or call */
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uint64_t lat_time; /* total latency time experienced */
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};
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/* lightweight tasks, without priority, mainly used for I/Os */
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struct tasklet {
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TASK_COMMON; /* must be at the beginning! */
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struct list list;
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};
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#define TASK_IS_TASKLET(t) ((t)->nice == -32768)
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/*
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* The task callback (->process) is responsible for updating ->expire. It must
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* return a pointer to the task itself, except if the task has been deleted, in
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* which case it returns NULL so that the scheduler knows it must not check the
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* expire timer. The scheduler will requeue the task at the proper location.
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*/
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#endif /* _TYPES_TASK_H */
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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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