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thread-pool: avoid per-thread-pool EventNotifier 

EventNotifier is implemented using an eventfd or pipe.  It therefore
consumes file descriptors, which can be limited by rlimits and should
therefore be used sparingly.

Switch from EventNotifier to QEMUBH in thread-pool.c.  Originally
EventNotifier was used because qemu_bh_schedule() was not thread-safe
yet.

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2014-07-15 16:44:25 +02:00 committed by Kevin Wolf
parent 2a87151fb2
commit c2e50e3d11
1 changed files with 8 additions and 13 deletions
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21
thread-pool.c
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@ -21,7 +21,6 @@
#include "block/coroutine.h"
#include "trace.h"
#include "block/block_int.h"
#include "qemu/event_notifier.h"
#include "block/thread-pool.h"
#include "qemu/main-loop.h"
@ -57,8 +56,8 @@ struct ThreadPoolElement {
};
struct ThreadPool {
EventNotifier notifier;
AioContext *ctx;
QEMUBH *completion_bh;
QemuMutex lock;
QemuCond check_cancel;
QemuCond worker_stopped;
@ -119,7 +118,7 @@ static void *worker_thread(void *opaque)
qemu_cond_broadcast(&pool->check_cancel);
}
event_notifier_set(&pool->notifier);
qemu_bh_schedule(pool->completion_bh);
}
pool->cur_threads--;
@ -168,12 +167,11 @@ static void spawn_thread(ThreadPool *pool)
}
}
static void event_notifier_ready(EventNotifier *notifier)
static void thread_pool_completion_bh(void *opaque)
{
ThreadPool *pool = container_of(notifier, ThreadPool, notifier);
ThreadPool *pool = opaque;
ThreadPoolElement *elem, *next;
event_notifier_test_and_clear(notifier);
restart:
QLIST_FOREACH_SAFE(elem, &pool->head, all, next) {
if (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {
@ -215,7 +213,7 @@ static void thread_pool_cancel(BlockDriverAIOCB *acb)
qemu_sem_timedwait(&pool->sem, 0) == 0) {
QTAILQ_REMOVE(&pool->request_list, elem, reqs);
elem->state = THREAD_CANCELED;
event_notifier_set(&pool->notifier);
qemu_bh_schedule(pool->completion_bh);
} else {
pool->pending_cancellations++;
while (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {
@ -224,7 +222,7 @@ static void thread_pool_cancel(BlockDriverAIOCB *acb)
pool->pending_cancellations--;
}
qemu_mutex_unlock(&pool->lock);
event_notifier_ready(&pool->notifier);
thread_pool_completion_bh(pool);
}
static const AIOCBInfo thread_pool_aiocb_info = {
@ -293,8 +291,8 @@ static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
}
memset(pool, 0, sizeof(*pool));
event_notifier_init(&pool->notifier, false);
pool->ctx = ctx;
pool->completion_bh = aio_bh_new(ctx, thread_pool_completion_bh, pool);
qemu_mutex_init(&pool->lock);
qemu_cond_init(&pool->check_cancel);
qemu_cond_init(&pool->worker_stopped);
@ -304,8 +302,6 @@ static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
QLIST_INIT(&pool->head);
QTAILQ_INIT(&pool->request_list);
aio_set_event_notifier(ctx, &pool->notifier, event_notifier_ready);
}
ThreadPool *thread_pool_new(AioContext *ctx)
@ -339,11 +335,10 @@ void thread_pool_free(ThreadPool *pool)
qemu_mutex_unlock(&pool->lock);
aio_set_event_notifier(pool->ctx, &pool->notifier, NULL);
qemu_bh_delete(pool->completion_bh);
qemu_sem_destroy(&pool->sem);
qemu_cond_destroy(&pool->check_cancel);
qemu_cond_destroy(&pool->worker_stopped);
qemu_mutex_destroy(&pool->lock);
event_notifier_cleanup(&pool->notifier);
g_free(pool);
}