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avoid potential RC on ctx->threadLimit (gh-4547), code review #4601

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Merged
terrelln merged 1 commit into from
Mar 2, 2026
+16 −19
Merged

avoid potential RC on ctx->threadLimit (gh-4547), code review #4601

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35 changes: 16 additions & 19 deletions lib/common/pool.c
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Original file line number Diff line number Diff line change
Expand Up @@ -142,19 +142,17 @@ POOL_ctx* POOL_create_advanced(size_t numThreads, size_t queueSize,
/* 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 */
{ size_t i;
for (i = 0; i < numThreads; ++i) {
if (ZSTD_pthread_create(&ctx->threads[i], NULL, &POOL_thread, ctx)) {
ctx->threadCapacity = i;
POOL_free(ctx);
return NULL;
} }
ctx->threadCapacity = numThreads;
ctx->threadLimit = numThreads;
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;
}
Expand Down Expand Up @@ -220,23 +218,22 @@ static int POOL_resize_internal(POOL_ctx* ctx, size_t numThreads)
return 0;
}
/* numThreads > threadCapacity */
ctx->threadLimit = numThreads;
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@terrelln terrelln Mar 2, 2026

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This is a minor change in behavior when an operation fails below, but it seems fine & slightly preferable.

{ ZSTD_pthread_t* const threadPool = (ZSTD_pthread_t*)ZSTD_customCalloc(numThreads * sizeof(ZSTD_pthread_t), ctx->customMem);
if (!threadPool) return 1;
/* replace existing thread pool */
/* 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 */
{ size_t threadId;
for (threadId = ctx->threadCapacity; threadId < numThreads; ++threadId) {
if (ZSTD_pthread_create(&threadPool[threadId], NULL, &POOL_thread, ctx)) {
ctx->threadCapacity = threadId;
return 1;
} }
} }
while (ctx->threadCapacity < numThreads) {
if (ZSTD_pthread_create(&threadPool[ctx->threadCapacity++], NULL, &POOL_thread, ctx)) {
--ctx->threadCapacity;
return 1;
}
}
}
/* successfully expanded */
ctx->threadCapacity = numThreads;
ctx->threadLimit = numThreads;
return 0;
}

Expand Down