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The taskq_t's active thread list is sorted based on its tqt_ent->tqent_id field. The list is kept sorted solely by inserting new taskq_thread_t's in their correct sorted location; no other means is used. This means that once inserted, if a taskq_thread_t's tqt_ent->tqent_id field changes, the list runs the risk of no longer being sorted. Prior to the introduction of the taskq_dispatch_prealloc() interface, this was not a problem as a taskq_ent_t actively being serviced under the old interface should always have a static tqent_id field. Thus, once the taskq_thread_t is added to the taskq_t's active thread list, the taskq_thread_t's tqt_ent->tqent_id field would remain constant. Now, this is no longer the case. Currently, if using the taskq_dispatch_prealloc() interface, any given taskq_ent_t actively being serviced _may_ have its tqent_id value incremented. This happens when the preallocated taskq_ent_t structure is recursively dispatched. Thus, a taskq_thread_t could potentially have its tqt_ent->tqent_id field silently modified from under its feet. If this were to happen to a taskq_thread_t on a taskq_t's active thread list, this would compromise the integrity of the order of the list (as the list _may_ no longer be sorted). To get around this, the taskq_thread_t's taskq_ent_t pointer was replaced with its own static copy of the tqent_id. So, as a taskq_ent_t is pulled off of the taskq_t's pending list, a static copy of its tqent_id is made and this copy is used to sort the active thread list. Using a static copy is key in ensuring the integrity of the order of the active thread list. Even if the underlying taskq_ent_t is recursively dispatched (as has its tqent_id modified), this static copy stored inside the taskq_thread_t will remain constant. Signed-off-by: Prakash Surya <surya1@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #71
133 lines
5.5 KiB
C
133 lines
5.5 KiB
C
/*****************************************************************************\
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://github.com/behlendorf/spl/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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\*****************************************************************************/
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#ifndef _SPL_TASKQ_H
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#define _SPL_TASKQ_H
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#include <linux/module.h>
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#include <linux/gfp.h>
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#include <linux/slab.h>
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#include <linux/interrupt.h>
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#include <linux/kthread.h>
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#include <sys/types.h>
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#include <sys/thread.h>
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#define TASKQ_NAMELEN 31
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#define TASKQ_PREPOPULATE 0x00000001
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#define TASKQ_CPR_SAFE 0x00000002
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#define TASKQ_DYNAMIC 0x00000004
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#define TASKQ_THREADS_CPU_PCT 0x00000008
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#define TASKQ_DC_BATCH 0x00000010
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#define TASKQ_NORECLAIM 0x00000020
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typedef unsigned long taskqid_t;
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typedef void (task_func_t)(void *);
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typedef struct taskq_ent {
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spinlock_t tqent_lock;
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struct list_head tqent_list;
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taskqid_t tqent_id;
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task_func_t *tqent_func;
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void *tqent_arg;
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uintptr_t tqent_flags;
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} taskq_ent_t;
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#define TQENT_FLAG_PREALLOC 0x1
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/*
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* Flags for taskq_dispatch. TQ_SLEEP/TQ_NOSLEEP should be same as
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* KM_SLEEP/KM_NOSLEEP. TQ_NOQUEUE/TQ_NOALLOC are set particularly
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* large so as not to conflict with already used GFP_* defines.
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*/
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#define TQ_SLEEP KM_SLEEP
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#define TQ_NOSLEEP KM_NOSLEEP
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#define TQ_NOQUEUE 0x01000000
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#define TQ_NOALLOC 0x02000000
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#define TQ_NEW 0x04000000
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#define TQ_FRONT 0x08000000
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#define TQ_ACTIVE 0x80000000
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typedef struct taskq {
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spinlock_t tq_lock; /* protects taskq_t */
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unsigned long tq_lock_flags; /* interrupt state */
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const char *tq_name; /* taskq name */
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struct list_head tq_thread_list;/* list of all threads */
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struct list_head tq_active_list;/* list of active threads */
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int tq_nactive; /* # of active threads */
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int tq_nthreads; /* # of total threads */
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int tq_pri; /* priority */
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int tq_minalloc; /* min task_t pool size */
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int tq_maxalloc; /* max task_t pool size */
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int tq_nalloc; /* cur task_t pool size */
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uint_t tq_flags; /* flags */
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taskqid_t tq_next_id; /* next pend/work id */
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taskqid_t tq_lowest_id; /* lowest pend/work id */
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struct list_head tq_free_list; /* free task_t's */
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struct list_head tq_pend_list; /* pending task_t's */
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struct list_head tq_prio_list; /* priority pending task_t's */
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wait_queue_head_t tq_work_waitq; /* new work waitq */
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wait_queue_head_t tq_wait_waitq; /* wait waitq */
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} taskq_t;
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typedef struct taskq_thread {
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struct list_head tqt_thread_list;
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struct list_head tqt_active_list;
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struct task_struct *tqt_thread;
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taskq_t *tqt_tq;
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taskqid_t tqt_id;
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} taskq_thread_t;
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/* Global system-wide dynamic task queue available for all consumers */
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extern taskq_t *system_taskq;
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extern taskqid_t __taskq_dispatch(taskq_t *, task_func_t, void *, uint_t);
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extern void __taskq_dispatch_ent(taskq_t *, task_func_t, void *, uint_t, taskq_ent_t *);
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extern int __taskq_empty_ent(taskq_ent_t *);
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extern void __taskq_init_ent(taskq_ent_t *);
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extern taskq_t *__taskq_create(const char *, int, pri_t, int, int, uint_t);
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extern void __taskq_destroy(taskq_t *);
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extern void __taskq_wait_id(taskq_t *, taskqid_t);
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extern void __taskq_wait(taskq_t *);
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extern int __taskq_member(taskq_t *, void *);
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int spl_taskq_init(void);
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void spl_taskq_fini(void);
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#define taskq_member(tq, t) __taskq_member(tq, t)
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#define taskq_wait_id(tq, id) __taskq_wait_id(tq, id)
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#define taskq_wait(tq) __taskq_wait(tq)
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#define taskq_dispatch(tq, f, p, fl) __taskq_dispatch(tq, f, p, fl)
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#define taskq_dispatch_ent(tq, f, p, fl, t) __taskq_dispatch_ent(tq, f, p, fl, t)
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#define taskq_empty_ent(t) __taskq_empty_ent(t)
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#define taskq_init_ent(t) __taskq_init_ent(t)
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#define taskq_create(n, th, p, mi, ma, fl) __taskq_create(n, th, p, mi, ma, fl)
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#define taskq_create_proc(n, th, p, mi, ma, pr, fl) \
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__taskq_create(n, th, p, mi, ma, fl)
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#define taskq_create_sysdc(n, th, mi, ma, pr, dc, fl) \
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__taskq_create(n, th, maxclsyspri, mi, ma, fl)
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#define taskq_destroy(tq) __taskq_destroy(tq)
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#endif /* _SPL_TASKQ_H */
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