From 59ad7697705a65940f6370c28729aff87d446b46 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marek=20Ol=C5=A1=C3=A1k?= Date: Mon, 10 Jul 2017 21:17:04 +0200 Subject: util/u_queue: add an option to resize the queue when it's full MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Consider the following situation: mtx_lock(mutex); do_something(); util_queue_add_job(...); mtx_unlock(mutex); If the queue is full, util_queue_add_job will wait for a free slot. If the job which is currently being executed tries to lock the mutex, it will be stuck forever, because util_queue_add_job is stuck. The deadlock can be trivially resolved by increasing the queue size (reallocating the queue) in util_queue_add_job if the queue is full. Then util_queue_add_job becomes wait-free. radeonsi will use it. Reviewed-by: Nicolai Hähnle --- src/util/u_queue.c | 37 ++++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-) (limited to 'src/util/u_queue.c') diff --git a/src/util/u_queue.c b/src/util/u_queue.c index cb5903014e7..49361c3dadf 100644 --- a/src/util/u_queue.c +++ b/src/util/u_queue.c @@ -204,6 +204,7 @@ util_queue_init(struct util_queue *queue, memset(queue, 0, sizeof(*queue)); queue->name = name; + queue->flags = flags; queue->num_threads = num_threads; queue->max_jobs = max_jobs; @@ -329,9 +330,39 @@ util_queue_add_job(struct util_queue *queue, assert(queue->num_queued >= 0 && queue->num_queued <= queue->max_jobs); - /* if the queue is full, wait until there is space */ - while (queue->num_queued == queue->max_jobs) - cnd_wait(&queue->has_space_cond, &queue->lock); + if (queue->num_queued == queue->max_jobs) { + if (queue->flags & UTIL_QUEUE_INIT_RESIZE_IF_FULL) { + /* If the queue is full, make it larger to avoid waiting for a free + * slot. + */ + unsigned new_max_jobs = queue->max_jobs + 8; + struct util_queue_job *jobs = + (struct util_queue_job*)calloc(new_max_jobs, + sizeof(struct util_queue_job)); + assert(jobs); + + /* Copy all queued jobs into the new list. */ + unsigned num_jobs = 0; + unsigned i = queue->read_idx; + + do { + jobs[num_jobs++] = queue->jobs[i]; + i = (i + 1) % queue->max_jobs; + } while (i != queue->write_idx); + + assert(num_jobs == queue->num_queued); + + free(queue->jobs); + queue->jobs = jobs; + queue->read_idx = 0; + queue->write_idx = num_jobs; + queue->max_jobs = new_max_jobs; + } else { + /* Wait until there is a free slot. */ + while (queue->num_queued == queue->max_jobs) + cnd_wait(&queue->has_space_cond, &queue->lock); + } + } ptr = &queue->jobs[queue->write_idx]; assert(ptr->job == NULL); -- cgit v1.2.3