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Diffstat (limited to 'sys/cddl/contrib/opensolaris/uts/common/os/taskq.c')
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diff --git a/sys/cddl/contrib/opensolaris/uts/common/os/taskq.c b/sys/cddl/contrib/opensolaris/uts/common/os/taskq.c new file mode 100644 index 0000000..efaea2e --- /dev/null +++ b/sys/cddl/contrib/opensolaris/uts/common/os/taskq.c @@ -0,0 +1,1020 @@ +/* + * CDDL HEADER START + * + * The contents of this file are subject to the terms of the + * Common Development and Distribution License, Version 1.0 only + * (the "License"). You may not use this file except in compliance + * with the License. + * + * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE + * or http://www.opensolaris.org/os/licensing. + * See the License for the specific language governing permissions + * and limitations under the License. + * + * When distributing Covered Code, include this CDDL HEADER in each + * file and include the License file at usr/src/OPENSOLARIS.LICENSE. + * If applicable, add the following below this CDDL HEADER, with the + * fields enclosed by brackets "[]" replaced with your own identifying + * information: Portions Copyright [yyyy] [name of copyright owner] + * + * CDDL HEADER END + */ +/* + * Copyright 2005 Sun Microsystems, Inc. All rights reserved. + * Use is subject to license terms. + */ + +#pragma ident "%Z%%M% %I% %E% SMI" + +/* + * Kernel task queues: general-purpose asynchronous task scheduling. + * + * A common problem in kernel programming is the need to schedule tasks + * to be performed later, by another thread. There are several reasons + * you may want or need to do this: + * + * (1) The task isn't time-critical, but your current code path is. + * + * (2) The task may require grabbing locks that you already hold. + * + * (3) The task may need to block (e.g. to wait for memory), but you + * cannot block in your current context. + * + * (4) Your code path can't complete because of some condition, but you can't + * sleep or fail, so you queue the task for later execution when condition + * disappears. + * + * (5) You just want a simple way to launch multiple tasks in parallel. + * + * Task queues provide such a facility. In its simplest form (used when + * performance is not a critical consideration) a task queue consists of a + * single list of tasks, together with one or more threads to service the + * list. There are some cases when this simple queue is not sufficient: + * + * (1) The task queues are very hot and there is a need to avoid data and lock + * contention over global resources. + * + * (2) Some tasks may depend on other tasks to complete, so they can't be put in + * the same list managed by the same thread. + * + * (3) Some tasks may block for a long time, and this should not block other + * tasks in the queue. + * + * To provide useful service in such cases we define a "dynamic task queue" + * which has an individual thread for each of the tasks. These threads are + * dynamically created as they are needed and destroyed when they are not in + * use. The API for managing task pools is the same as for managing task queues + * with the exception of a taskq creation flag TASKQ_DYNAMIC which tells that + * dynamic task pool behavior is desired. + * + * Dynamic task queues may also place tasks in the normal queue (called "backing + * queue") when task pool runs out of resources. Users of task queues may + * disallow such queued scheduling by specifying TQ_NOQUEUE in the dispatch + * flags. + * + * The backing task queue is also used for scheduling internal tasks needed for + * dynamic task queue maintenance. + * + * INTERFACES: + * + * taskq_t *taskq_create(name, nthreads, pri_t pri, minalloc, maxall, flags); + * + * Create a taskq with specified properties. + * Possible 'flags': + * + * TASKQ_DYNAMIC: Create task pool for task management. If this flag is + * specified, 'nthreads' specifies the maximum number of threads in + * the task queue. Task execution order for dynamic task queues is + * not predictable. + * + * If this flag is not specified (default case) a + * single-list task queue is created with 'nthreads' threads + * servicing it. Entries in this queue are managed by + * taskq_ent_alloc() and taskq_ent_free() which try to keep the + * task population between 'minalloc' and 'maxalloc', but the + * latter limit is only advisory for TQ_SLEEP dispatches and the + * former limit is only advisory for TQ_NOALLOC dispatches. If + * TASKQ_PREPOPULATE is set in 'flags', the taskq will be + * prepopulated with 'minalloc' task structures. + * + * Since non-DYNAMIC taskqs are queues, tasks are guaranteed to be + * executed in the order they are scheduled if nthreads == 1. + * If nthreads > 1, task execution order is not predictable. + * + * TASKQ_PREPOPULATE: Prepopulate task queue with threads. + * Also prepopulate the task queue with 'minalloc' task structures. + * + * TASKQ_CPR_SAFE: This flag specifies that users of the task queue will + * use their own protocol for handling CPR issues. This flag is not + * supported for DYNAMIC task queues. + * + * The 'pri' field specifies the default priority for the threads that + * service all scheduled tasks. + * + * void taskq_destroy(tap): + * + * Waits for any scheduled tasks to complete, then destroys the taskq. + * Caller should guarantee that no new tasks are scheduled in the closing + * taskq. + * + * taskqid_t taskq_dispatch(tq, func, arg, flags): + * + * Dispatches the task "func(arg)" to taskq. The 'flags' indicates whether + * the caller is willing to block for memory. The function returns an + * opaque value which is zero iff dispatch fails. If flags is TQ_NOSLEEP + * or TQ_NOALLOC and the task can't be dispatched, taskq_dispatch() fails + * and returns (taskqid_t)0. + * + * ASSUMES: func != NULL. + * + * Possible flags: + * TQ_NOSLEEP: Do not wait for resources; may fail. + * + * TQ_NOALLOC: Do not allocate memory; may fail. May only be used with + * non-dynamic task queues. + * + * TQ_NOQUEUE: Do not enqueue a task if it can't dispatch it due to + * lack of available resources and fail. If this flag is not + * set, and the task pool is exhausted, the task may be scheduled + * in the backing queue. This flag may ONLY be used with dynamic + * task queues. + * + * NOTE: This flag should always be used when a task queue is used + * for tasks that may depend on each other for completion. + * Enqueueing dependent tasks may create deadlocks. + * + * TQ_SLEEP: May block waiting for resources. May still fail for + * dynamic task queues if TQ_NOQUEUE is also specified, otherwise + * always succeed. + * + * NOTE: Dynamic task queues are much more likely to fail in + * taskq_dispatch() (especially if TQ_NOQUEUE was specified), so it + * is important to have backup strategies handling such failures. + * + * void taskq_wait(tq): + * + * Waits for all previously scheduled tasks to complete. + * + * NOTE: It does not stop any new task dispatches. + * Do NOT call taskq_wait() from a task: it will cause deadlock. + * + * void taskq_suspend(tq) + * + * Suspend all task execution. Tasks already scheduled for a dynamic task + * queue will still be executed, but all new scheduled tasks will be + * suspended until taskq_resume() is called. + * + * int taskq_suspended(tq) + * + * Returns 1 if taskq is suspended and 0 otherwise. It is intended to + * ASSERT that the task queue is suspended. + * + * void taskq_resume(tq) + * + * Resume task queue execution. + * + * int taskq_member(tq, thread) + * + * Returns 1 if 'thread' belongs to taskq 'tq' and 0 otherwise. The + * intended use is to ASSERT that a given function is called in taskq + * context only. + * + * system_taskq + * + * Global system-wide dynamic task queue for common uses. It may be used by + * any subsystem that needs to schedule tasks and does not need to manage + * its own task queues. It is initialized quite early during system boot. + * + * IMPLEMENTATION. + * + * This is schematic representation of the task queue structures. + * + * taskq: + * +-------------+ + * |tq_lock | +---< taskq_ent_free() + * +-------------+ | + * |... | | tqent: tqent: + * +-------------+ | +------------+ +------------+ + * | tq_freelist |-->| tqent_next |--> ... ->| tqent_next | + * +-------------+ +------------+ +------------+ + * |... | | ... | | ... | + * +-------------+ +------------+ +------------+ + * | tq_task | | + * | | +-------------->taskq_ent_alloc() + * +--------------------------------------------------------------------------+ + * | | | tqent tqent | + * | +---------------------+ +--> +------------+ +--> +------------+ | + * | | ... | | | func, arg | | | func, arg | | + * +>+---------------------+ <---|-+ +------------+ <---|-+ +------------+ | + * | tq_taskq.tqent_next | ----+ | | tqent_next | --->+ | | tqent_next |--+ + * +---------------------+ | +------------+ ^ | +------------+ + * +-| tq_task.tqent_prev | +--| tqent_prev | | +--| tqent_prev | ^ + * | +---------------------+ +------------+ | +------------+ | + * | |... | | ... | | | ... | | + * | +---------------------+ +------------+ | +------------+ | + * | ^ | | + * | | | | + * +--------------------------------------+--------------+ TQ_APPEND() -+ + * | | | + * |... | taskq_thread()-----+ + * +-------------+ + * | tq_buckets |--+-------> [ NULL ] (for regular task queues) + * +-------------+ | + * | DYNAMIC TASK QUEUES: + * | + * +-> taskq_bucket[nCPU] taskq_bucket_dispatch() + * +-------------------+ ^ + * +--->| tqbucket_lock | | + * | +-------------------+ +--------+ +--------+ + * | | tqbucket_freelist |-->| tqent |-->...| tqent | ^ + * | +-------------------+<--+--------+<--...+--------+ | + * | | ... | | thread | | thread | | + * | +-------------------+ +--------+ +--------+ | + * | +-------------------+ | + * taskq_dispatch()--+--->| tqbucket_lock | TQ_APPEND()------+ + * TQ_HASH() | +-------------------+ +--------+ +--------+ + * | | tqbucket_freelist |-->| tqent |-->...| tqent | + * | +-------------------+<--+--------+<--...+--------+ + * | | ... | | thread | | thread | + * | +-------------------+ +--------+ +--------+ + * +---> ... + * + * + * Task queues use tq_task field to link new entry in the queue. The queue is a + * circular doubly-linked list. Entries are put in the end of the list with + * TQ_APPEND() and processed from the front of the list by taskq_thread() in + * FIFO order. Task queue entries are cached in the free list managed by + * taskq_ent_alloc() and taskq_ent_free() functions. + * + * All threads used by task queues mark t_taskq field of the thread to + * point to the task queue. + * + * Dynamic Task Queues Implementation. + * + * For a dynamic task queues there is a 1-to-1 mapping between a thread and + * taskq_ent_structure. Each entry is serviced by its own thread and each thread + * is controlled by a single entry. + * + * Entries are distributed over a set of buckets. To avoid using modulo + * arithmetics the number of buckets is 2^n and is determined as the nearest + * power of two roundown of the number of CPUs in the system. Tunable + * variable 'taskq_maxbuckets' limits the maximum number of buckets. Each entry + * is attached to a bucket for its lifetime and can't migrate to other buckets. + * + * Entries that have scheduled tasks are not placed in any list. The dispatch + * function sets their "func" and "arg" fields and signals the corresponding + * thread to execute the task. Once the thread executes the task it clears the + * "func" field and places an entry on the bucket cache of free entries pointed + * by "tqbucket_freelist" field. ALL entries on the free list should have "func" + * field equal to NULL. The free list is a circular doubly-linked list identical + * in structure to the tq_task list above, but entries are taken from it in LIFO + * order - the last freed entry is the first to be allocated. The + * taskq_bucket_dispatch() function gets the most recently used entry from the + * free list, sets its "func" and "arg" fields and signals a worker thread. + * + * After executing each task a per-entry thread taskq_d_thread() places its + * entry on the bucket free list and goes to a timed sleep. If it wakes up + * without getting new task it removes the entry from the free list and destroys + * itself. The thread sleep time is controlled by a tunable variable + * `taskq_thread_timeout'. + * + * There is various statistics kept in the bucket which allows for later + * analysis of taskq usage patterns. Also, a global copy of taskq creation and + * death statistics is kept in the global taskq data structure. Since thread + * creation and death happen rarely, updating such global data does not present + * a performance problem. + * + * NOTE: Threads are not bound to any CPU and there is absolutely no association + * between the bucket and actual thread CPU, so buckets are used only to + * split resources and reduce resource contention. Having threads attached + * to the CPU denoted by a bucket may reduce number of times the job + * switches between CPUs. + * + * Current algorithm creates a thread whenever a bucket has no free + * entries. It would be nice to know how many threads are in the running + * state and don't create threads if all CPUs are busy with existing + * tasks, but it is unclear how such strategy can be implemented. + * + * Currently buckets are created statically as an array attached to task + * queue. On some system with nCPUs < max_ncpus it may waste system + * memory. One solution may be allocation of buckets when they are first + * touched, but it is not clear how useful it is. + * + * SUSPEND/RESUME implementation. + * + * Before executing a task taskq_thread() (executing non-dynamic task + * queues) obtains taskq's thread lock as a reader. The taskq_suspend() + * function gets the same lock as a writer blocking all non-dynamic task + * execution. The taskq_resume() function releases the lock allowing + * taskq_thread to continue execution. + * + * For dynamic task queues, each bucket is marked as TQBUCKET_SUSPEND by + * taskq_suspend() function. After that taskq_bucket_dispatch() always + * fails, so that taskq_dispatch() will either enqueue tasks for a + * suspended backing queue or fail if TQ_NOQUEUE is specified in dispatch + * flags. + * + * NOTE: taskq_suspend() does not immediately block any tasks already + * scheduled for dynamic task queues. It only suspends new tasks + * scheduled after taskq_suspend() was called. + * + * taskq_member() function works by comparing a thread t_taskq pointer with + * the passed thread pointer. + * + * LOCKS and LOCK Hierarchy: + * + * There are two locks used in task queues. + * + * 1) Task queue structure has a lock, protecting global task queue state. + * + * 2) Each per-CPU bucket has a lock for bucket management. + * + * If both locks are needed, task queue lock should be taken only after bucket + * lock. + * + * DEBUG FACILITIES. + * + * For DEBUG kernels it is possible to induce random failures to + * taskq_dispatch() function when it is given TQ_NOSLEEP argument. The value of + * taskq_dmtbf and taskq_smtbf tunables control the mean time between induced + * failures for dynamic and static task queues respectively. + * + * Setting TASKQ_STATISTIC to 0 will disable per-bucket statistics. + * + * TUNABLES + * + * system_taskq_size - Size of the global system_taskq. + * This value is multiplied by nCPUs to determine + * actual size. + * Default value: 64 + * + * taskq_thread_timeout - Maximum idle time for taskq_d_thread() + * Default value: 5 minutes + * + * taskq_maxbuckets - Maximum number of buckets in any task queue + * Default value: 128 + * + * taskq_search_depth - Maximum # of buckets searched for a free entry + * Default value: 4 + * + * taskq_dmtbf - Mean time between induced dispatch failures + * for dynamic task queues. + * Default value: UINT_MAX (no induced failures) + * + * taskq_smtbf - Mean time between induced dispatch failures + * for static task queues. + * Default value: UINT_MAX (no induced failures) + * + * CONDITIONAL compilation. + * + * TASKQ_STATISTIC - If set will enable bucket statistic (default). + * + */ + +#include <sys/taskq_impl.h> +#include <sys/proc.h> +#include <sys/kmem.h> +#include <sys/callb.h> +#include <sys/systm.h> +#include <sys/cmn_err.h> +#include <sys/debug.h> +#include <sys/sysmacros.h> +#include <sys/sdt.h> +#include <sys/mutex.h> +#include <sys/kernel.h> +#include <sys/limits.h> + +static kmem_cache_t *taskq_ent_cache, *taskq_cache; + +/* Global system task queue for common use */ +taskq_t *system_taskq; + +/* + * Maxmimum number of entries in global system taskq is + * system_taskq_size * max_ncpus + */ +#define SYSTEM_TASKQ_SIZE 64 +int system_taskq_size = SYSTEM_TASKQ_SIZE; + +/* + * Dynamic task queue threads that don't get any work within + * taskq_thread_timeout destroy themselves + */ +#define TASKQ_THREAD_TIMEOUT (60 * 5) +int taskq_thread_timeout = TASKQ_THREAD_TIMEOUT; + +#define TASKQ_MAXBUCKETS 128 +int taskq_maxbuckets = TASKQ_MAXBUCKETS; + +/* + * When a bucket has no available entries another buckets are tried. + * taskq_search_depth parameter limits the amount of buckets that we search + * before failing. This is mostly useful in systems with many CPUs where we may + * spend too much time scanning busy buckets. + */ +#define TASKQ_SEARCH_DEPTH 4 +int taskq_search_depth = TASKQ_SEARCH_DEPTH; + +/* + * Hashing function: mix various bits of x. May be pretty much anything. + */ +#define TQ_HASH(x) ((x) ^ ((x) >> 11) ^ ((x) >> 17) ^ ((x) ^ 27)) + +/* + * We do not create any new threads when the system is low on memory and start + * throttling memory allocations. The following macro tries to estimate such + * condition. + */ +#define ENOUGH_MEMORY() (freemem > throttlefree) + +/* + * Static functions. + */ +static taskq_t *taskq_create_common(const char *, int, int, pri_t, int, + int, uint_t); +static void taskq_thread(void *); +static int taskq_constructor(void *, void *, int); +static void taskq_destructor(void *, void *); +static int taskq_ent_constructor(void *, void *, int); +static void taskq_ent_destructor(void *, void *); +static taskq_ent_t *taskq_ent_alloc(taskq_t *, int); +static void taskq_ent_free(taskq_t *, taskq_ent_t *); + +/* + * Collect per-bucket statistic when TASKQ_STATISTIC is defined. + */ +#define TASKQ_STATISTIC 1 + +#if TASKQ_STATISTIC +#define TQ_STAT(b, x) b->tqbucket_stat.x++ +#else +#define TQ_STAT(b, x) +#endif + +/* + * Random fault injection. + */ +uint_t taskq_random; +uint_t taskq_dmtbf = UINT_MAX; /* mean time between injected failures */ +uint_t taskq_smtbf = UINT_MAX; /* mean time between injected failures */ + +/* + * TQ_NOSLEEP dispatches on dynamic task queues are always allowed to fail. + * + * TQ_NOSLEEP dispatches on static task queues can't arbitrarily fail because + * they could prepopulate the cache and make sure that they do not use more + * then minalloc entries. So, fault injection in this case insures that + * either TASKQ_PREPOPULATE is not set or there are more entries allocated + * than is specified by minalloc. TQ_NOALLOC dispatches are always allowed + * to fail, but for simplicity we treat them identically to TQ_NOSLEEP + * dispatches. + */ +#ifdef DEBUG +#define TASKQ_D_RANDOM_DISPATCH_FAILURE(tq, flag) \ + taskq_random = (taskq_random * 2416 + 374441) % 1771875;\ + if ((flag & TQ_NOSLEEP) && \ + taskq_random < 1771875 / taskq_dmtbf) { \ + return (NULL); \ + } + +#define TASKQ_S_RANDOM_DISPATCH_FAILURE(tq, flag) \ + taskq_random = (taskq_random * 2416 + 374441) % 1771875;\ + if ((flag & (TQ_NOSLEEP | TQ_NOALLOC)) && \ + (!(tq->tq_flags & TASKQ_PREPOPULATE) || \ + (tq->tq_nalloc > tq->tq_minalloc)) && \ + (taskq_random < (1771875 / taskq_smtbf))) { \ + mutex_exit(&tq->tq_lock); \ + return ((taskqid_t)0); \ + } +#else +#define TASKQ_S_RANDOM_DISPATCH_FAILURE(tq, flag) +#define TASKQ_D_RANDOM_DISPATCH_FAILURE(tq, flag) +#endif + +#define IS_EMPTY(l) (((l).tqent_prev == (l).tqent_next) && \ + ((l).tqent_prev == &(l))) + +/* + * Append `tqe' in the end of the doubly-linked list denoted by l. + */ +#define TQ_APPEND(l, tqe) { \ + tqe->tqent_next = &l; \ + tqe->tqent_prev = l.tqent_prev; \ + tqe->tqent_next->tqent_prev = tqe; \ + tqe->tqent_prev->tqent_next = tqe; \ +} + +/* + * Schedule a task specified by func and arg into the task queue entry tqe. + */ +#define TQ_ENQUEUE(tq, tqe, func, arg) { \ + ASSERT(MUTEX_HELD(&tq->tq_lock)); \ + TQ_APPEND(tq->tq_task, tqe); \ + tqe->tqent_func = (func); \ + tqe->tqent_arg = (arg); \ + tq->tq_tasks++; \ + if (tq->tq_tasks - tq->tq_executed > tq->tq_maxtasks) \ + tq->tq_maxtasks = tq->tq_tasks - tq->tq_executed; \ + cv_signal(&tq->tq_dispatch_cv); \ + DTRACE_PROBE2(taskq__enqueue, taskq_t *, tq, taskq_ent_t *, tqe); \ +} + +/* + * Do-nothing task which may be used to prepopulate thread caches. + */ +/*ARGSUSED*/ +void +nulltask(void *unused) +{ +} + + +/*ARGSUSED*/ +static int +taskq_constructor(void *buf, void *cdrarg, int kmflags) +{ + taskq_t *tq = buf; + + bzero(tq, sizeof (taskq_t)); + + mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL); + rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL); + cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL); + cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL); + + tq->tq_task.tqent_next = &tq->tq_task; + tq->tq_task.tqent_prev = &tq->tq_task; + + return (0); +} + +/*ARGSUSED*/ +static void +taskq_destructor(void *buf, void *cdrarg) +{ + taskq_t *tq = buf; + + mutex_destroy(&tq->tq_lock); + rw_destroy(&tq->tq_threadlock); + cv_destroy(&tq->tq_dispatch_cv); + cv_destroy(&tq->tq_wait_cv); +} + +/*ARGSUSED*/ +static int +taskq_ent_constructor(void *buf, void *cdrarg, int kmflags) +{ + taskq_ent_t *tqe = buf; + + tqe->tqent_thread = NULL; + cv_init(&tqe->tqent_cv, NULL, CV_DEFAULT, NULL); + + return (0); +} + +/*ARGSUSED*/ +static void +taskq_ent_destructor(void *buf, void *cdrarg) +{ + taskq_ent_t *tqe = buf; + + ASSERT(tqe->tqent_thread == NULL); + cv_destroy(&tqe->tqent_cv); +} + +/* + * Create global system dynamic task queue. + */ +void +system_taskq_init(void) +{ + system_taskq = taskq_create_common("system_taskq", 0, + system_taskq_size * max_ncpus, minclsyspri, 4, 512, + TASKQ_PREPOPULATE); +} + +void +system_taskq_fini(void) +{ + taskq_destroy(system_taskq); +} + +static void +taskq_init(void *dummy __unused) +{ + taskq_ent_cache = kmem_cache_create("taskq_ent_cache", + sizeof (taskq_ent_t), 0, taskq_ent_constructor, + taskq_ent_destructor, NULL, NULL, NULL, 0); + taskq_cache = kmem_cache_create("taskq_cache", sizeof (taskq_t), + 0, taskq_constructor, taskq_destructor, NULL, NULL, NULL, 0); + system_taskq_init(); +} + +static void +taskq_fini(void *dummy __unused) +{ + system_taskq_fini(); + kmem_cache_destroy(taskq_cache); + kmem_cache_destroy(taskq_ent_cache); +} + +/* + * taskq_ent_alloc() + * + * Allocates a new taskq_ent_t structure either from the free list or from the + * cache. Returns NULL if it can't be allocated. + * + * Assumes: tq->tq_lock is held. + */ +static taskq_ent_t * +taskq_ent_alloc(taskq_t *tq, int flags) +{ + int kmflags = (flags & TQ_NOSLEEP) ? KM_NOSLEEP : KM_SLEEP; + + taskq_ent_t *tqe; + + ASSERT(MUTEX_HELD(&tq->tq_lock)); + + /* + * TQ_NOALLOC allocations are allowed to use the freelist, even if + * we are below tq_minalloc. + */ + if ((tqe = tq->tq_freelist) != NULL && + ((flags & TQ_NOALLOC) || tq->tq_nalloc >= tq->tq_minalloc)) { + tq->tq_freelist = tqe->tqent_next; + } else { + if (flags & TQ_NOALLOC) + return (NULL); + + mutex_exit(&tq->tq_lock); + if (tq->tq_nalloc >= tq->tq_maxalloc) { + if (kmflags & KM_NOSLEEP) { + mutex_enter(&tq->tq_lock); + return (NULL); + } + /* + * We don't want to exceed tq_maxalloc, but we can't + * wait for other tasks to complete (and thus free up + * task structures) without risking deadlock with + * the caller. So, we just delay for one second + * to throttle the allocation rate. + */ + delay(hz); + } + tqe = kmem_cache_alloc(taskq_ent_cache, kmflags); + mutex_enter(&tq->tq_lock); + if (tqe != NULL) + tq->tq_nalloc++; + } + return (tqe); +} + +/* + * taskq_ent_free() + * + * Free taskq_ent_t structure by either putting it on the free list or freeing + * it to the cache. + * + * Assumes: tq->tq_lock is held. + */ +static void +taskq_ent_free(taskq_t *tq, taskq_ent_t *tqe) +{ + ASSERT(MUTEX_HELD(&tq->tq_lock)); + + if (tq->tq_nalloc <= tq->tq_minalloc) { + tqe->tqent_next = tq->tq_freelist; + tq->tq_freelist = tqe; + } else { + tq->tq_nalloc--; + mutex_exit(&tq->tq_lock); + kmem_cache_free(taskq_ent_cache, tqe); + mutex_enter(&tq->tq_lock); + } +} + +/* + * Dispatch a task. + * + * Assumes: func != NULL + * + * Returns: NULL if dispatch failed. + * non-NULL if task dispatched successfully. + * Actual return value is the pointer to taskq entry that was used to + * dispatch a task. This is useful for debugging. + */ +/* ARGSUSED */ +taskqid_t +taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags) +{ + taskq_ent_t *tqe = NULL; + + ASSERT(tq != NULL); + ASSERT(func != NULL); + ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC)); + + /* + * TQ_NOQUEUE flag can't be used with non-dynamic task queues. + */ + ASSERT(! (flags & TQ_NOQUEUE)); + + /* + * Enqueue the task to the underlying queue. + */ + mutex_enter(&tq->tq_lock); + + TASKQ_S_RANDOM_DISPATCH_FAILURE(tq, flags); + + if ((tqe = taskq_ent_alloc(tq, flags)) == NULL) { + mutex_exit(&tq->tq_lock); + return ((taskqid_t)NULL); + } + TQ_ENQUEUE(tq, tqe, func, arg); + mutex_exit(&tq->tq_lock); + return ((taskqid_t)tqe); +} + +/* + * Wait for all pending tasks to complete. + * Calling taskq_wait from a task will cause deadlock. + */ +void +taskq_wait(taskq_t *tq) +{ + + mutex_enter(&tq->tq_lock); + while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0) + cv_wait(&tq->tq_wait_cv, &tq->tq_lock); + mutex_exit(&tq->tq_lock); +} + +/* + * Suspend execution of tasks. + * + * Tasks in the queue part will be suspended immediately upon return from this + * function. Pending tasks in the dynamic part will continue to execute, but all + * new tasks will be suspended. + */ +void +taskq_suspend(taskq_t *tq) +{ + rw_enter(&tq->tq_threadlock, RW_WRITER); + + /* + * Mark task queue as being suspended. Needed for taskq_suspended(). + */ + mutex_enter(&tq->tq_lock); + ASSERT(!(tq->tq_flags & TASKQ_SUSPENDED)); + tq->tq_flags |= TASKQ_SUSPENDED; + mutex_exit(&tq->tq_lock); +} + +/* + * returns: 1 if tq is suspended, 0 otherwise. + */ +int +taskq_suspended(taskq_t *tq) +{ + return ((tq->tq_flags & TASKQ_SUSPENDED) != 0); +} + +/* + * Resume taskq execution. + */ +void +taskq_resume(taskq_t *tq) +{ + ASSERT(RW_WRITE_HELD(&tq->tq_threadlock)); + + mutex_enter(&tq->tq_lock); + ASSERT(tq->tq_flags & TASKQ_SUSPENDED); + tq->tq_flags &= ~TASKQ_SUSPENDED; + mutex_exit(&tq->tq_lock); + + rw_exit(&tq->tq_threadlock); +} + +/* + * Worker thread for processing task queue. + */ +static void +taskq_thread(void *arg) +{ + taskq_t *tq = arg; + taskq_ent_t *tqe; + callb_cpr_t cprinfo; + hrtime_t start, end; + + CALLB_CPR_INIT(&cprinfo, &tq->tq_lock, callb_generic_cpr, tq->tq_name); + + mutex_enter(&tq->tq_lock); + while (tq->tq_flags & TASKQ_ACTIVE) { + if ((tqe = tq->tq_task.tqent_next) == &tq->tq_task) { + if (--tq->tq_active == 0) + cv_broadcast(&tq->tq_wait_cv); + if (tq->tq_flags & TASKQ_CPR_SAFE) { + cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock); + } else { + CALLB_CPR_SAFE_BEGIN(&cprinfo); + cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock); + CALLB_CPR_SAFE_END(&cprinfo, &tq->tq_lock); + } + tq->tq_active++; + continue; + } + tqe->tqent_prev->tqent_next = tqe->tqent_next; + tqe->tqent_next->tqent_prev = tqe->tqent_prev; + mutex_exit(&tq->tq_lock); + + rw_enter(&tq->tq_threadlock, RW_READER); + start = gethrtime(); + DTRACE_PROBE2(taskq__exec__start, taskq_t *, tq, + taskq_ent_t *, tqe); + tqe->tqent_func(tqe->tqent_arg); + DTRACE_PROBE2(taskq__exec__end, taskq_t *, tq, + taskq_ent_t *, tqe); + end = gethrtime(); + rw_exit(&tq->tq_threadlock); + + mutex_enter(&tq->tq_lock); + tq->tq_totaltime += end - start; + tq->tq_executed++; + + taskq_ent_free(tq, tqe); + } + tq->tq_nthreads--; + cv_broadcast(&tq->tq_wait_cv); + ASSERT(!(tq->tq_flags & TASKQ_CPR_SAFE)); + CALLB_CPR_EXIT(&cprinfo); + thread_exit(); +} + +/* + * Taskq creation. May sleep for memory. + * Always use automatically generated instances to avoid kstat name space + * collisions. + */ + +taskq_t * +taskq_create(const char *name, int nthreads, pri_t pri, int minalloc, + int maxalloc, uint_t flags) +{ + return taskq_create_common(name, 0, nthreads, pri, minalloc, + maxalloc, flags | TASKQ_NOINSTANCE); +} + +static taskq_t * +taskq_create_common(const char *name, int instance, int nthreads, pri_t pri, + int minalloc, int maxalloc, uint_t flags) +{ + taskq_t *tq = kmem_cache_alloc(taskq_cache, KM_SLEEP); + uint_t ncpus = ((boot_max_ncpus == -1) ? max_ncpus : boot_max_ncpus); + uint_t bsize; /* # of buckets - always power of 2 */ + + ASSERT(instance == 0); + ASSERT(flags == TASKQ_PREPOPULATE | TASKQ_NOINSTANCE); + + /* + * TASKQ_CPR_SAFE and TASKQ_DYNAMIC flags are mutually exclusive. + */ + ASSERT((flags & (TASKQ_DYNAMIC | TASKQ_CPR_SAFE)) != + ((TASKQ_DYNAMIC | TASKQ_CPR_SAFE))); + + ASSERT(tq->tq_buckets == NULL); + + bsize = 1 << (highbit(ncpus) - 1); + ASSERT(bsize >= 1); + bsize = MIN(bsize, taskq_maxbuckets); + + tq->tq_maxsize = nthreads; + + (void) strncpy(tq->tq_name, name, TASKQ_NAMELEN + 1); + tq->tq_name[TASKQ_NAMELEN] = '\0'; + /* Make sure the name conforms to the rules for C indentifiers */ + strident_canon(tq->tq_name, TASKQ_NAMELEN); + + tq->tq_flags = flags | TASKQ_ACTIVE; + tq->tq_active = nthreads; + tq->tq_nthreads = nthreads; + tq->tq_minalloc = minalloc; + tq->tq_maxalloc = maxalloc; + tq->tq_nbuckets = bsize; + tq->tq_pri = pri; + + if (flags & TASKQ_PREPOPULATE) { + mutex_enter(&tq->tq_lock); + while (minalloc-- > 0) + taskq_ent_free(tq, taskq_ent_alloc(tq, TQ_SLEEP)); + mutex_exit(&tq->tq_lock); + } + + if (nthreads == 1) { + tq->tq_thread = thread_create(NULL, 0, taskq_thread, tq, + 0, NULL, TS_RUN, pri); + } else { + kthread_t **tpp = kmem_alloc(sizeof (kthread_t *) * nthreads, + KM_SLEEP); + + tq->tq_threadlist = tpp; + + mutex_enter(&tq->tq_lock); + while (nthreads-- > 0) { + *tpp = thread_create(NULL, 0, taskq_thread, tq, + 0, NULL, TS_RUN, pri); + tpp++; + } + mutex_exit(&tq->tq_lock); + } + + return (tq); +} + +/* + * taskq_destroy(). + * + * Assumes: by the time taskq_destroy is called no one will use this task queue + * in any way and no one will try to dispatch entries in it. + */ +void +taskq_destroy(taskq_t *tq) +{ + taskq_bucket_t *b = tq->tq_buckets; + int bid = 0; + + ASSERT(! (tq->tq_flags & TASKQ_CPR_SAFE)); + + /* + * Wait for any pending entries to complete. + */ + taskq_wait(tq); + + mutex_enter(&tq->tq_lock); + ASSERT((tq->tq_task.tqent_next == &tq->tq_task) && + (tq->tq_active == 0)); + + if ((tq->tq_nthreads > 1) && (tq->tq_threadlist != NULL)) + kmem_free(tq->tq_threadlist, sizeof (kthread_t *) * + tq->tq_nthreads); + + tq->tq_flags &= ~TASKQ_ACTIVE; + cv_broadcast(&tq->tq_dispatch_cv); + while (tq->tq_nthreads != 0) + cv_wait(&tq->tq_wait_cv, &tq->tq_lock); + + tq->tq_minalloc = 0; + while (tq->tq_nalloc != 0) + taskq_ent_free(tq, taskq_ent_alloc(tq, TQ_SLEEP)); + + mutex_exit(&tq->tq_lock); + + /* + * Mark each bucket as closing and wakeup all sleeping threads. + */ + for (; (b != NULL) && (bid < tq->tq_nbuckets); b++, bid++) { + taskq_ent_t *tqe; + + mutex_enter(&b->tqbucket_lock); + + b->tqbucket_flags |= TQBUCKET_CLOSE; + /* Wakeup all sleeping threads */ + + for (tqe = b->tqbucket_freelist.tqent_next; + tqe != &b->tqbucket_freelist; tqe = tqe->tqent_next) + cv_signal(&tqe->tqent_cv); + + ASSERT(b->tqbucket_nalloc == 0); + + /* + * At this point we waited for all pending jobs to complete (in + * both the task queue and the bucket and no new jobs should + * arrive. Wait for all threads to die. + */ + while (b->tqbucket_nfree > 0) + cv_wait(&b->tqbucket_cv, &b->tqbucket_lock); + mutex_exit(&b->tqbucket_lock); + mutex_destroy(&b->tqbucket_lock); + cv_destroy(&b->tqbucket_cv); + } + + if (tq->tq_buckets != NULL) { + ASSERT(tq->tq_flags & TASKQ_DYNAMIC); + kmem_free(tq->tq_buckets, + sizeof (taskq_bucket_t) * tq->tq_nbuckets); + + /* Cleanup fields before returning tq to the cache */ + tq->tq_buckets = NULL; + tq->tq_tcreates = 0; + tq->tq_tdeaths = 0; + } else { + ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC)); + } + + tq->tq_totaltime = 0; + tq->tq_tasks = 0; + tq->tq_maxtasks = 0; + tq->tq_executed = 0; + kmem_cache_free(taskq_cache, tq); +} + +SYSINIT(sol_taskq, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, taskq_init, NULL) +SYSUNINIT(sol_taskq, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, taskq_fini, NULL); |
