/src/zstd/lib/common/pool.c

Source
/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */


/* ======   Dependencies   ======= */
#include "../common/allocations.h"  /* ZSTD_customCalloc, ZSTD_customFree */
#include "zstd_deps.h" /* size_t */
#include "debug.h"     /* assert */
#include "pool.h"

/* ======   Compiler specifics   ====== */
#if defined(_MSC_VER)
#  pragma warning(disable : 4204)        /* disable: C4204: non-constant aggregate initializer */
#endif


#ifdef ZSTD_MULTITHREAD

#include "threading.h"   /* pthread adaptation */

/* A job is a function and an opaque argument */
typedef struct POOL_job_s {
    POOL_function function;
    void *opaque;
} POOL_job;

struct POOL_ctx_s {
    ZSTD_customMem customMem;
    /* Keep track of the threads */
    ZSTD_pthread_t* threads;
    size_t threadCapacity;
    size_t threadLimit;

    /* The queue is a circular buffer */
    POOL_job *queue;
    size_t queueHead;
    size_t queueTail;
    size_t queueSize;

    /* The number of threads working on jobs */
    size_t numThreadsBusy;
    /* Indicates if the queue is empty */
    int queueEmpty;

    /* The mutex protects the queue */
    ZSTD_pthread_mutex_t queueMutex;
    /* Condition variable for pushers to wait on when the queue is full */
    ZSTD_pthread_cond_t queuePushCond;
    /* Condition variables for poppers to wait on when the queue is empty */
    ZSTD_pthread_cond_t queuePopCond;
    /* Indicates if the queue is shutting down */
    int shutdown;
};

/* POOL_thread() :
 * Work thread for the thread pool.
 * Waits for jobs and executes them.
 * @returns : NULL on failure else non-null.
 */
static void* POOL_thread(void* opaque) {
    POOL_ctx* const ctx = (POOL_ctx*)opaque;
    if (!ctx) { return NULL; }
    for (;;) {
        /* Lock the mutex and wait for a non-empty queue or until shutdown */
        ZSTD_pthread_mutex_lock(&ctx->queueMutex);

        while ( ctx->queueEmpty
            || (ctx->numThreadsBusy >= ctx->threadLimit) ) {
            if (ctx->shutdown) {
                /* even if !queueEmpty, (possible if numThreadsBusy >= threadLimit),
                 * a few threads will be shutdown while !queueEmpty,
                 * but enough threads will remain active to finish the queue */
                ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
                return opaque;
            }
            ZSTD_pthread_cond_wait(&ctx->queuePopCond, &ctx->queueMutex);
        }
        /* Pop a job off the queue */
        {   POOL_job const job = ctx->queue[ctx->queueHead];
            ctx->queueHead = (ctx->queueHead + 1) % ctx->queueSize;
            ctx->numThreadsBusy++;
            ctx->queueEmpty = (ctx->queueHead == ctx->queueTail);
            /* Unlock the mutex, signal a pusher, and run the job */
            ZSTD_pthread_cond_signal(&ctx->queuePushCond);
            ZSTD_pthread_mutex_unlock(&ctx->queueMutex);

            job.function(job.opaque);

            /* If the intended queue size was 0, signal after finishing job */
            ZSTD_pthread_mutex_lock(&ctx->queueMutex);
            ctx->numThreadsBusy--;
            ZSTD_pthread_cond_signal(&ctx->queuePushCond);
            ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
        }
    }  /* for (;;) */
    assert(0);  /* Unreachable */
}

/* ZSTD_createThreadPool() : public access point */
POOL_ctx* ZSTD_createThreadPool(size_t numThreads) {
    return POOL_create (numThreads, 0);
}

POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
    return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
}

POOL_ctx* POOL_create_advanced(size_t numThreads, size_t queueSize,
                               ZSTD_customMem customMem)
{
    POOL_ctx* ctx;
    /* Check parameters */
    if (!numThreads) { return NULL; }
    /* Allocate the context and zero initialize */
    ctx = (POOL_ctx*)ZSTD_customCalloc(sizeof(POOL_ctx), customMem);
    if (!ctx) { return NULL; }
    /* Initialize the job queue.
     * It needs one extra space since one space is wasted to differentiate
     * empty and full queues.
     */
    ctx->queueSize = queueSize + 1;
    ctx->queue = (POOL_job*)ZSTD_customCalloc(ctx->queueSize * sizeof(POOL_job), customMem);
    ctx->queueHead = 0;
    ctx->queueTail = 0;
    ctx->numThreadsBusy = 0;
    ctx->queueEmpty = 1;
    {
        int error = 0;
        error |= ZSTD_pthread_mutex_init(&ctx->queueMutex, NULL);
        error |= ZSTD_pthread_cond_init(&ctx->queuePushCond, NULL);
        error |= ZSTD_pthread_cond_init(&ctx->queuePopCond, NULL);
        if (error) { POOL_free(ctx); return NULL; }
    }
    ctx->shutdown = 0;
    /* Allocate space for the thread handles */
    ctx->threads = (ZSTD_pthread_t*)ZSTD_customCalloc(numThreads * sizeof(ZSTD_pthread_t), customMem);
    ctx->threadCapacity = 0;
    ctx->threadLimit = numThreads;
    ctx->customMem = customMem;
    /* Check for errors */
    if (!ctx->threads || !ctx->queue) { POOL_free(ctx); return NULL; }
    /* Initialize the threads */
    while (ctx->threadCapacity < numThreads) {
        if (ZSTD_pthread_create(&ctx->threads[ctx->threadCapacity++], NULL, &POOL_thread, ctx)) {
            --ctx->threadCapacity;
            POOL_free(ctx);
            return NULL;
        }
    }
    return ctx;
}

/*! POOL_join() :
    Shutdown the queue, wake any sleeping threads, and join all of the threads.
*/
static void POOL_join(POOL_ctx* ctx) {
    /* Shut down the queue */
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    ctx->shutdown = 1;
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
    /* Wake up sleeping threads */
    ZSTD_pthread_cond_broadcast(&ctx->queuePushCond);
    ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
    /* Join all of the threads */
    {   size_t i;
        for (i = 0; i < ctx->threadCapacity; ++i) {
            ZSTD_pthread_join(ctx->threads[i]);  /* note : could fail */
    }   }
}

void POOL_free(POOL_ctx *ctx) {
    if (!ctx) { return; }
    POOL_join(ctx);
    ZSTD_pthread_mutex_destroy(&ctx->queueMutex);
    ZSTD_pthread_cond_destroy(&ctx->queuePushCond);
    ZSTD_pthread_cond_destroy(&ctx->queuePopCond);
    ZSTD_customFree(ctx->queue, ctx->customMem);
    ZSTD_customFree(ctx->threads, ctx->customMem);
    ZSTD_customFree(ctx, ctx->customMem);
}

/*! POOL_joinJobs() :
 *  Waits for all queued jobs to finish executing.
 */
void POOL_joinJobs(POOL_ctx* ctx) {
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    while(!ctx->queueEmpty || ctx->numThreadsBusy > 0) {
        ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
    }
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
}

void ZSTD_freeThreadPool (ZSTD_threadPool* pool) {
  POOL_free (pool);
}

size_t POOL_sizeof(const POOL_ctx* ctx) {
    if (ctx==NULL) return 0;  /* supports sizeof NULL */
    return sizeof(*ctx)
        + ctx->queueSize * sizeof(POOL_job)
        + ctx->threadCapacity * sizeof(ZSTD_pthread_t);
}


/* @return : 0 on success, 1 on error */
static int POOL_resize_internal(POOL_ctx* ctx, size_t numThreads)
{
    if (numThreads <= ctx->threadCapacity) {
        if (!numThreads) return 1;
        ctx->threadLimit = numThreads;
        return 0;
    }
    /* numThreads > threadCapacity */
    ctx->threadLimit = numThreads;
    {   ZSTD_pthread_t* const threadPool = (ZSTD_pthread_t*)ZSTD_customCalloc(numThreads * sizeof(ZSTD_pthread_t), ctx->customMem);
        if (!threadPool) return 1;
        /* extend existing thread pool */
        ZSTD_memcpy(threadPool, ctx->threads, ctx->threadCapacity * sizeof(ZSTD_pthread_t));
        ZSTD_customFree(ctx->threads, ctx->customMem);
        ctx->threads = threadPool;
        /* Initialize additional threads */
        while (ctx->threadCapacity < numThreads) {
            if (ZSTD_pthread_create(&threadPool[ctx->threadCapacity++], NULL, &POOL_thread, ctx)) {
                --ctx->threadCapacity;
                return 1;
            }
        }
    }
    /* successfully expanded */
    return 0;
}

/* @return : 0 on success, 1 on error */
int POOL_resize(POOL_ctx* ctx, size_t numThreads)
{
    int result;
    if (ctx==NULL) return 1;
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    result = POOL_resize_internal(ctx, numThreads);
    ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
    return result;
}

/**
 * Returns 1 if the queue is full and 0 otherwise.
 *
 * When queueSize is 1 (pool was created with an intended queueSize of 0),
 * then a queue is empty if there is a thread free _and_ no job is waiting.
 */
static int isQueueFull(POOL_ctx const* ctx) {
    if (ctx->queueSize > 1) {
        return ctx->queueHead == ((ctx->queueTail + 1) % ctx->queueSize);
    } else {
        return (ctx->numThreadsBusy == ctx->threadLimit) ||
               !ctx->queueEmpty;
    }
}


static void
POOL_add_internal(POOL_ctx* ctx, POOL_function function, void *opaque)
{
    POOL_job job;
    job.function = function;
    job.opaque = opaque;
    assert(ctx != NULL);
    if (ctx->shutdown) return;

    ctx->queueEmpty = 0;
    ctx->queue[ctx->queueTail] = job;
    ctx->queueTail = (ctx->queueTail + 1) % ctx->queueSize;
    ZSTD_pthread_cond_signal(&ctx->queuePopCond);
}

void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque)
{
    assert(ctx != NULL);
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    /* Wait until there is space in the queue for the new job */
    while (isQueueFull(ctx) && (!ctx->shutdown)) {
        ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
    }
    POOL_add_internal(ctx, function, opaque);
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
}


int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque)
{
    assert(ctx != NULL);
    ZSTD_pthread_mutex_lock(&ctx->queueMutex);
    if (isQueueFull(ctx)) {
        ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
        return 0;
    }
    POOL_add_internal(ctx, function, opaque);
    ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
    return 1;
}


#else  /* ZSTD_MULTITHREAD  not defined */

/* ========================== */
/* No multi-threading support */
/* ========================== */


/* We don't need any data, but if it is empty, malloc() might return NULL. */
struct POOL_ctx_s {
    int dummy;
};
static POOL_ctx g_poolCtx;

POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
    return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
}

POOL_ctx*
POOL_create_advanced(size_t numThreads, size_t queueSize, ZSTD_customMem customMem)
{
    (void)numThreads;
    (void)queueSize;
    (void)customMem;
    return &g_poolCtx;
}

void POOL_free(POOL_ctx* ctx) {
    assert(!ctx || ctx == &g_poolCtx);
    (void)ctx;
}

void POOL_joinJobs(POOL_ctx* ctx){
    assert(!ctx || ctx == &g_poolCtx);
    (void)ctx;
}

int POOL_resize(POOL_ctx* ctx, size_t numThreads) {
    (void)ctx; (void)numThreads;
    return 0;
}

void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque) {
    (void)ctx;
    function(opaque);
}

int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque) {
    (void)ctx;
    function(opaque);
    return 1;
}

size_t POOL_sizeof(const POOL_ctx* ctx) {
    if (ctx==NULL) return 0;  /* supports sizeof NULL */
    assert(ctx == &g_poolCtx);
    return sizeof(*ctx);
}

#endif  /* ZSTD_MULTITHREAD */

Coverage Report

Created: 2026-03-12 07:14

Line	Count	Source
1		/*
2		* Copyright (c) Meta Platforms, Inc. and affiliates.
3		* All rights reserved.
4		*
5		* This source code is licensed under both the BSD-style license (found in the
6		* LICENSE file in the root directory of this source tree) and the GPLv2 (found
7		* in the COPYING file in the root directory of this source tree).
8		* You may select, at your option, one of the above-listed licenses.
9		*/
10
11
12		/* ====== Dependencies ======= */
13		#include "../common/allocations.h" /* ZSTD_customCalloc, ZSTD_customFree */
14		#include "zstd_deps.h" /* size_t */
15		#include "debug.h" /* assert */
16		#include "pool.h"
17
18		/* ====== Compiler specifics ====== */
19		#if defined(_MSC_VER)
20		# pragma warning(disable : 4204) /* disable: C4204: non-constant aggregate initializer */
21		#endif
22
23
24		#ifdef ZSTD_MULTITHREAD
25
26		#include "threading.h" /* pthread adaptation */
27
28		/* A job is a function and an opaque argument */
29		typedef struct POOL_job_s {
30		POOL_function function;
31		void *opaque;
32		} POOL_job;
33
34		struct POOL_ctx_s {
35		ZSTD_customMem customMem;
36		/* Keep track of the threads */
37		ZSTD_pthread_t* threads;
38		size_t threadCapacity;
39		size_t threadLimit;
40
41		/* The queue is a circular buffer */
42		POOL_job *queue;
43		size_t queueHead;
44		size_t queueTail;
45		size_t queueSize;
46
47		/* The number of threads working on jobs */
48		size_t numThreadsBusy;
49		/* Indicates if the queue is empty */
50		int queueEmpty;
51
52		/* The mutex protects the queue */
53		ZSTD_pthread_mutex_t queueMutex;
54		/* Condition variable for pushers to wait on when the queue is full */
55		ZSTD_pthread_cond_t queuePushCond;
56		/* Condition variables for poppers to wait on when the queue is empty */
57		ZSTD_pthread_cond_t queuePopCond;
58		/* Indicates if the queue is shutting down */
59		int shutdown;
60		};
61
62		/* POOL_thread() :
63		* Work thread for the thread pool.
64		* Waits for jobs and executes them.
65		* @returns : NULL on failure else non-null.
66		*/
67	0	static void* POOL_thread(void* opaque) {
68	0	POOL_ctx* const ctx = (POOL_ctx*)opaque;
69	0	if (!ctx) { return NULL; }
70	0	for (;;) {
71		/* Lock the mutex and wait for a non-empty queue or until shutdown */
72	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
73
74	0	while ( ctx->queueEmpty
75	0	\|\| (ctx->numThreadsBusy >= ctx->threadLimit) ) {
76	0	if (ctx->shutdown) {
77		/* even if !queueEmpty, (possible if numThreadsBusy >= threadLimit),
78		* a few threads will be shutdown while !queueEmpty,
79		* but enough threads will remain active to finish the queue */
80	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
81	0	return opaque;
82	0	}
83	0	ZSTD_pthread_cond_wait(&ctx->queuePopCond, &ctx->queueMutex);
84	0	}
85		/* Pop a job off the queue */
86	0	{ POOL_job const job = ctx->queue[ctx->queueHead];
87	0	ctx->queueHead = (ctx->queueHead + 1) % ctx->queueSize;
88	0	ctx->numThreadsBusy++;
89	0	ctx->queueEmpty = (ctx->queueHead == ctx->queueTail);
90		/* Unlock the mutex, signal a pusher, and run the job */
91	0	ZSTD_pthread_cond_signal(&ctx->queuePushCond);
92	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
93
94	0	job.function(job.opaque);
95
96		/* If the intended queue size was 0, signal after finishing job */
97	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
98	0	ctx->numThreadsBusy--;
99	0	ZSTD_pthread_cond_signal(&ctx->queuePushCond);
100	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
101	0	}
102	0	} /* for (;;) */
103	0	assert(0); /* Unreachable */
104	0	}
105
106		/* ZSTD_createThreadPool() : public access point */
107	0	POOL_ctx* ZSTD_createThreadPool(size_t numThreads) {
108	0	return POOL_create (numThreads, 0);
109	0	}
110
111	0	POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
112	0	return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
113	0	}
114
115		POOL_ctx* POOL_create_advanced(size_t numThreads, size_t queueSize,
116		ZSTD_customMem customMem)
117	0	{
118	0	POOL_ctx* ctx;
119		/* Check parameters */
120	0	if (!numThreads) { return NULL; }
121		/* Allocate the context and zero initialize */
122	0	ctx = (POOL_ctx*)ZSTD_customCalloc(sizeof(POOL_ctx), customMem);
123	0	if (!ctx) { return NULL; }
124		/* Initialize the job queue.
125		* It needs one extra space since one space is wasted to differentiate
126		* empty and full queues.
127		*/
128	0	ctx->queueSize = queueSize + 1;
129	0	ctx->queue = (POOL_job)ZSTD_customCalloc(ctx->queueSize sizeof(POOL_job), customMem);
130	0	ctx->queueHead = 0;
131	0	ctx->queueTail = 0;
132	0	ctx->numThreadsBusy = 0;
133	0	ctx->queueEmpty = 1;
134	0	{
135	0	int error = 0;
136	0	error \|= ZSTD_pthread_mutex_init(&ctx->queueMutex, NULL);
137	0	error \|= ZSTD_pthread_cond_init(&ctx->queuePushCond, NULL);
138	0	error \|= ZSTD_pthread_cond_init(&ctx->queuePopCond, NULL);
139	0	if (error) { POOL_free(ctx); return NULL; }
140	0	}
141	0	ctx->shutdown = 0;
142		/* Allocate space for the thread handles */
143	0	ctx->threads = (ZSTD_pthread_t)ZSTD_customCalloc(numThreads sizeof(ZSTD_pthread_t), customMem);
144	0	ctx->threadCapacity = 0;
145	0	ctx->threadLimit = numThreads;
146	0	ctx->customMem = customMem;
147		/* Check for errors */
148	0	if (!ctx->threads \|\| !ctx->queue) { POOL_free(ctx); return NULL; }
149		/* Initialize the threads */
150	0	while (ctx->threadCapacity < numThreads) {
151	0	if (ZSTD_pthread_create(&ctx->threads[ctx->threadCapacity++], NULL, &POOL_thread, ctx)) {
152	0	--ctx->threadCapacity;
153	0	POOL_free(ctx);
154	0	return NULL;
155	0	}
156	0	}
157	0	return ctx;
158	0	}
159
160		/*! POOL_join() :
161		Shutdown the queue, wake any sleeping threads, and join all of the threads.
162		*/
163	0	static void POOL_join(POOL_ctx* ctx) {
164		/* Shut down the queue */
165	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
166	0	ctx->shutdown = 1;
167	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
168		/* Wake up sleeping threads */
169	0	ZSTD_pthread_cond_broadcast(&ctx->queuePushCond);
170	0	ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
171		/* Join all of the threads */
172	0	{ size_t i;
173	0	for (i = 0; i < ctx->threadCapacity; ++i) {
174	0	ZSTD_pthread_join(ctx->threads[i]); /* note : could fail */
175	0	} }
176	0	}
177
178	0	void POOL_free(POOL_ctx *ctx) {
179	0	if (!ctx) { return; }
180	0	POOL_join(ctx);
181	0	ZSTD_pthread_mutex_destroy(&ctx->queueMutex);
182	0	ZSTD_pthread_cond_destroy(&ctx->queuePushCond);
183	0	ZSTD_pthread_cond_destroy(&ctx->queuePopCond);
184	0	ZSTD_customFree(ctx->queue, ctx->customMem);
185	0	ZSTD_customFree(ctx->threads, ctx->customMem);
186	0	ZSTD_customFree(ctx, ctx->customMem);
187	0	}
188
189		/*! POOL_joinJobs() :
190		* Waits for all queued jobs to finish executing.
191		*/
192	0	void POOL_joinJobs(POOL_ctx* ctx) {
193	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
194	0	while(!ctx->queueEmpty \|\| ctx->numThreadsBusy > 0) {
195	0	ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
196	0	}
197	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
198	0	}
199
200	0	void ZSTD_freeThreadPool (ZSTD_threadPool* pool) {
201	0	POOL_free (pool);
202	0	}
203
204	0	size_t POOL_sizeof(const POOL_ctx* ctx) {
205	0	if (ctx==NULL) return 0; /* supports sizeof NULL */
206	0	return sizeof(*ctx)
207	0	+ ctx->queueSize * sizeof(POOL_job)
208	0	+ ctx->threadCapacity * sizeof(ZSTD_pthread_t);
209	0	}
210
211
212		/* @return : 0 on success, 1 on error */
213		static int POOL_resize_internal(POOL_ctx* ctx, size_t numThreads)
214	0	{
215	0	if (numThreads <= ctx->threadCapacity) {
216	0	if (!numThreads) return 1;
217	0	ctx->threadLimit = numThreads;
218	0	return 0;
219	0	}
220		/* numThreads > threadCapacity */
221	0	ctx->threadLimit = numThreads;
222	0	{ ZSTD_pthread_t* const threadPool = (ZSTD_pthread_t)ZSTD_customCalloc(numThreads sizeof(ZSTD_pthread_t), ctx->customMem);
223	0	if (!threadPool) return 1;
224		/* extend existing thread pool */
225	0	ZSTD_memcpy(threadPool, ctx->threads, ctx->threadCapacity * sizeof(ZSTD_pthread_t));
226	0	ZSTD_customFree(ctx->threads, ctx->customMem);
227	0	ctx->threads = threadPool;
228		/* Initialize additional threads */
229	0	while (ctx->threadCapacity < numThreads) {
230	0	if (ZSTD_pthread_create(&threadPool[ctx->threadCapacity++], NULL, &POOL_thread, ctx)) {
231	0	--ctx->threadCapacity;
232	0	return 1;
233	0	}
234	0	}
235	0	}
236		/* successfully expanded */
237	0	return 0;
238	0	}
239
240		/* @return : 0 on success, 1 on error */
241		int POOL_resize(POOL_ctx* ctx, size_t numThreads)
242	0	{
243	0	int result;
244	0	if (ctx==NULL) return 1;
245	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
246	0	result = POOL_resize_internal(ctx, numThreads);
247	0	ZSTD_pthread_cond_broadcast(&ctx->queuePopCond);
248	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
249	0	return result;
250	0	}
251
252		/**
253		* Returns 1 if the queue is full and 0 otherwise.
254		*
255		* When queueSize is 1 (pool was created with an intended queueSize of 0),
256		* then a queue is empty if there is a thread free _and_ no job is waiting.
257		*/
258	0	static int isQueueFull(POOL_ctx const* ctx) {
259	0	if (ctx->queueSize > 1) {
260	0	return ctx->queueHead == ((ctx->queueTail + 1) % ctx->queueSize);
261	0	} else {
262	0	return (ctx->numThreadsBusy == ctx->threadLimit) \|\|
263	0	!ctx->queueEmpty;
264	0	}
265	0	}
266
267
268		static void
269		POOL_add_internal(POOL_ctx* ctx, POOL_function function, void *opaque)
270	0	{
271	0	POOL_job job;
272	0	job.function = function;
273	0	job.opaque = opaque;
274	0	assert(ctx != NULL);
275	0	if (ctx->shutdown) return;
276
277	0	ctx->queueEmpty = 0;
278	0	ctx->queue[ctx->queueTail] = job;
279	0	ctx->queueTail = (ctx->queueTail + 1) % ctx->queueSize;
280	0	ZSTD_pthread_cond_signal(&ctx->queuePopCond);
281	0	}
282
283		void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque)
284	0	{
285	0	assert(ctx != NULL);
286	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
287		/* Wait until there is space in the queue for the new job */
288	0	while (isQueueFull(ctx) && (!ctx->shutdown)) {
289	0	ZSTD_pthread_cond_wait(&ctx->queuePushCond, &ctx->queueMutex);
290	0	}
291	0	POOL_add_internal(ctx, function, opaque);
292	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
293	0	}
294
295
296		int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque)
297	0	{
298	0	assert(ctx != NULL);
299	0	ZSTD_pthread_mutex_lock(&ctx->queueMutex);
300	0	if (isQueueFull(ctx)) {
301	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
302	0	return 0;
303	0	}
304	0	POOL_add_internal(ctx, function, opaque);
305	0	ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
306	0	return 1;
307	0	}
308
309
310		#else /* ZSTD_MULTITHREAD not defined */
311
312		/* ========================== */
313		/* No multi-threading support */
314		/* ========================== */
315
316
317		/* We don't need any data, but if it is empty, malloc() might return NULL. */
318		struct POOL_ctx_s {
319		int dummy;
320		};
321		static POOL_ctx g_poolCtx;
322
323		POOL_ctx* POOL_create(size_t numThreads, size_t queueSize) {
324		return POOL_create_advanced(numThreads, queueSize, ZSTD_defaultCMem);
325		}
326
327		POOL_ctx*
328		POOL_create_advanced(size_t numThreads, size_t queueSize, ZSTD_customMem customMem)
329		{
330		(void)numThreads;
331		(void)queueSize;
332		(void)customMem;
333		return &g_poolCtx;
334		}
335
336		void POOL_free(POOL_ctx* ctx) {
337		assert(!ctx \|\| ctx == &g_poolCtx);
338		(void)ctx;
339		}
340
341		void POOL_joinJobs(POOL_ctx* ctx){
342		assert(!ctx \|\| ctx == &g_poolCtx);
343		(void)ctx;
344		}
345
346		int POOL_resize(POOL_ctx* ctx, size_t numThreads) {
347		(void)ctx; (void)numThreads;
348		return 0;
349		}
350
351		void POOL_add(POOL_ctx* ctx, POOL_function function, void* opaque) {
352		(void)ctx;
353		function(opaque);
354		}
355
356		int POOL_tryAdd(POOL_ctx* ctx, POOL_function function, void* opaque) {
357		(void)ctx;
358		function(opaque);
359		return 1;
360		}
361
362		size_t POOL_sizeof(const POOL_ctx* ctx) {
363		if (ctx==NULL) return 0; /* supports sizeof NULL */
364		assert(ctx == &g_poolCtx);
365		return sizeof(*ctx);
366		}
367
368		#endif /* ZSTD_MULTITHREAD */