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tcmu: fix unmap thread race
If the unmap thread has already run find_free_blocks but not yet run prepare_to_wait when a wake_up(&unmap_wait) call is done, the unmap thread is going to miss the wake call. Instead of adding checks for if new waiters were added this just has us use a work queue which will run us again in this type of case. Signed-off-by: Mike Christie <mchristi@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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parent
89ec9cfd3b
commit
9972cebb59
1 changed files with 10 additions and 33 deletions
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@ -32,7 +32,7 @@
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#include <linux/highmem.h>
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#include <linux/configfs.h>
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#include <linux/mutex.h>
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#include <linux/kthread.h>
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#include <linux/workqueue.h>
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#include <net/genetlink.h>
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#include <scsi/scsi_common.h>
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#include <scsi/scsi_proto.h>
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@ -176,12 +176,11 @@ struct tcmu_cmd {
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unsigned long flags;
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};
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static struct task_struct *unmap_thread;
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static wait_queue_head_t unmap_wait;
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static DEFINE_MUTEX(root_udev_mutex);
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static LIST_HEAD(root_udev);
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static atomic_t global_db_count = ATOMIC_INIT(0);
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static struct work_struct tcmu_unmap_work;
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static struct kmem_cache *tcmu_cmd_cache;
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@ -389,8 +388,7 @@ static bool tcmu_get_empty_blocks(struct tcmu_dev *udev,
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err:
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udev->waiting_global = true;
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/* Try to wake up the unmap thread */
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wake_up(&unmap_wait);
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schedule_work(&tcmu_unmap_work);
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return false;
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}
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@ -1065,8 +1063,7 @@ static void tcmu_device_timedout(struct timer_list *t)
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idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
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spin_unlock_irqrestore(&udev->commands_lock, flags);
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/* Try to wake up the ummap thread */
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wake_up(&unmap_wait);
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schedule_work(&tcmu_unmap_work);
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/*
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* We don't need to wakeup threads on wait_cmdr since they have their
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@ -2044,23 +2041,10 @@ static void run_cmdr_queues(void)
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mutex_unlock(&root_udev_mutex);
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}
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static int unmap_thread_fn(void *data)
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static void tcmu_unmap_work_fn(struct work_struct *work)
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{
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while (!kthread_should_stop()) {
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DEFINE_WAIT(__wait);
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prepare_to_wait(&unmap_wait, &__wait, TASK_INTERRUPTIBLE);
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schedule();
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finish_wait(&unmap_wait, &__wait);
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if (kthread_should_stop())
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break;
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find_free_blocks();
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run_cmdr_queues();
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}
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return 0;
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find_free_blocks();
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run_cmdr_queues();
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}
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static int __init tcmu_module_init(void)
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@ -2069,6 +2053,8 @@ static int __init tcmu_module_init(void)
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BUILD_BUG_ON((sizeof(struct tcmu_cmd_entry) % TCMU_OP_ALIGN_SIZE) != 0);
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INIT_WORK(&tcmu_unmap_work, tcmu_unmap_work_fn);
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tcmu_cmd_cache = kmem_cache_create("tcmu_cmd_cache",
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sizeof(struct tcmu_cmd),
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__alignof__(struct tcmu_cmd),
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@ -2114,17 +2100,8 @@ static int __init tcmu_module_init(void)
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if (ret)
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goto out_attrs;
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init_waitqueue_head(&unmap_wait);
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unmap_thread = kthread_run(unmap_thread_fn, NULL, "tcmu_unmap");
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if (IS_ERR(unmap_thread)) {
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ret = PTR_ERR(unmap_thread);
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goto out_unreg_transport;
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}
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return 0;
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out_unreg_transport:
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target_backend_unregister(&tcmu_ops);
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out_attrs:
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kfree(tcmu_attrs);
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out_unreg_genl:
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@ -2139,7 +2116,7 @@ static int __init tcmu_module_init(void)
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static void __exit tcmu_module_exit(void)
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{
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kthread_stop(unmap_thread);
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cancel_work_sync(&tcmu_unmap_work);
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target_backend_unregister(&tcmu_ops);
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kfree(tcmu_attrs);
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genl_unregister_family(&tcmu_genl_family);
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