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tcmu: fix unmap thread race

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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>
This commit is contained in:
Mike Christie 2017-11-28 12:40:30 -06:00 committed by Nicholas Bellinger
parent 89ec9cfd3b
commit 9972cebb59
1 changed files with 10 additions and 33 deletions
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43
drivers/target/target_core_user.c
View file

@ -32,7 +32,7 @@
#include <linux/highmem.h> #include <linux/highmem.h>
#include <linux/configfs.h> #include <linux/configfs.h>
#include <linux/mutex.h> #include <linux/mutex.h>
#include <linux/kthread.h> #include <linux/workqueue.h>
#include <net/genetlink.h> #include <net/genetlink.h>
#include <scsi/scsi_common.h> #include <scsi/scsi_common.h>
#include <scsi/scsi_proto.h> #include <scsi/scsi_proto.h>
@ -176,12 +176,11 @@ struct tcmu_cmd {
unsigned long flags; unsigned long flags;
}; };
static struct task_struct *unmap_thread;
static wait_queue_head_t unmap_wait;
static DEFINE_MUTEX(root_udev_mutex); static DEFINE_MUTEX(root_udev_mutex);
static LIST_HEAD(root_udev); static LIST_HEAD(root_udev);
static atomic_t global_db_count = ATOMIC_INIT(0); static atomic_t global_db_count = ATOMIC_INIT(0);
static struct work_struct tcmu_unmap_work;
static struct kmem_cache *tcmu_cmd_cache; static struct kmem_cache *tcmu_cmd_cache;
@ -389,8 +388,7 @@ static bool tcmu_get_empty_blocks(struct tcmu_dev *udev,
err: err:
udev->waiting_global = true; udev->waiting_global = true;
/* Try to wake up the unmap thread */ schedule_work(&tcmu_unmap_work);
wake_up(&unmap_wait);
return false; return false;
} }
@ -1065,8 +1063,7 @@ static void tcmu_device_timedout(struct timer_list *t)
idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL); idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
spin_unlock_irqrestore(&udev->commands_lock, flags); spin_unlock_irqrestore(&udev->commands_lock, flags);
/* Try to wake up the ummap thread */ schedule_work(&tcmu_unmap_work);
wake_up(&unmap_wait);
/* /*
* We don't need to wakeup threads on wait_cmdr since they have their * We don't need to wakeup threads on wait_cmdr since they have their
@ -2044,23 +2041,10 @@ static void run_cmdr_queues(void)
mutex_unlock(&root_udev_mutex); mutex_unlock(&root_udev_mutex);
} }
static int unmap_thread_fn(void *data) static void tcmu_unmap_work_fn(struct work_struct *work)
{ {
while (!kthread_should_stop()) { find_free_blocks();
DEFINE_WAIT(__wait); run_cmdr_queues();
prepare_to_wait(&unmap_wait, &__wait, TASK_INTERRUPTIBLE);
schedule();
finish_wait(&unmap_wait, &__wait);
if (kthread_should_stop())
break;
find_free_blocks();
run_cmdr_queues();
}
return 0;
} }
static int __init tcmu_module_init(void) static int __init tcmu_module_init(void)
@ -2069,6 +2053,8 @@ static int __init tcmu_module_init(void)
BUILD_BUG_ON((sizeof(struct tcmu_cmd_entry) % TCMU_OP_ALIGN_SIZE) != 0); BUILD_BUG_ON((sizeof(struct tcmu_cmd_entry) % TCMU_OP_ALIGN_SIZE) != 0);
INIT_WORK(&tcmu_unmap_work, tcmu_unmap_work_fn);
tcmu_cmd_cache = kmem_cache_create("tcmu_cmd_cache", tcmu_cmd_cache = kmem_cache_create("tcmu_cmd_cache",
sizeof(struct tcmu_cmd), sizeof(struct tcmu_cmd),
__alignof__(struct tcmu_cmd), __alignof__(struct tcmu_cmd),
@ -2114,17 +2100,8 @@ static int __init tcmu_module_init(void)
if (ret) if (ret)
goto out_attrs; goto out_attrs;
init_waitqueue_head(&unmap_wait);
unmap_thread = kthread_run(unmap_thread_fn, NULL, "tcmu_unmap");
if (IS_ERR(unmap_thread)) {
ret = PTR_ERR(unmap_thread);
goto out_unreg_transport;
}
return 0; return 0;
out_unreg_transport:
target_backend_unregister(&tcmu_ops);
out_attrs: out_attrs:
kfree(tcmu_attrs); kfree(tcmu_attrs);
out_unreg_genl: out_unreg_genl:
@ -2139,7 +2116,7 @@ static int __init tcmu_module_init(void)
static void __exit tcmu_module_exit(void) static void __exit tcmu_module_exit(void)
{ {
kthread_stop(unmap_thread); cancel_work_sync(&tcmu_unmap_work);
target_backend_unregister(&tcmu_ops); target_backend_unregister(&tcmu_ops);
kfree(tcmu_attrs); kfree(tcmu_attrs);
genl_unregister_family(&tcmu_genl_family); genl_unregister_family(&tcmu_genl_family);