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iw_cm: free cm_id resources on the last deref 

Remove the complicated logic to free the iw_cm_id inside iw_cm
event handlers vs when an application thread destroys the cm_id.
Also remove the block in iw_destroy_cm_id() to block the application
until all references are removed.  This block can cause a deadlock when
disconnecting or destroying cm_ids inside an rdma_cm event handler.
Simply allowing the last deref of the iw_cm_id to free the memory
is cleaner and avoids this potential deadlock. Also a flag is added,
IW_CM_DROP_EVENTS, that is set when the cm_id is marked for destruction.
If any events are pending on this iw_cm_id, then as they are processed
they will be dropped vs posted upstream if IW_CM_DROP_EVENTS is set.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
This commit is contained in:
Steve Wise 2016-07-29 11:00:54 -07:00 committed by Doug Ledford
parent ad61a4c7a9
commit 59c68ac31e
2 changed files with 18 additions and 38 deletions
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50
drivers/infiniband/core/iwcm.c
View File

@ -183,15 +183,14 @@ static void free_cm_id(struct iwcm_id_private *cm_id_priv)
/*
* Release a reference on cm_id. If the last reference is being
* released, enable the waiting thread (in iw_destroy_cm_id) to
* get woken up, and return 1 if a thread is already waiting.
* released, free the cm_id and return 1.
*/
static int iwcm_deref_id(struct iwcm_id_private *cm_id_priv)
{
BUG_ON(atomic_read(&cm_id_priv->refcount)==0);
if (atomic_dec_and_test(&cm_id_priv->refcount)) {
BUG_ON(!list_empty(&cm_id_priv->work_list));
complete(&cm_id_priv->destroy_comp);
free_cm_id(cm_id_priv);
return 1;
}
@ -208,19 +207,10 @@ static void add_ref(struct iw_cm_id *cm_id)
static void rem_ref(struct iw_cm_id *cm_id)
{
struct iwcm_id_private *cm_id_priv;
int cb_destroy;
cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
/*
* Test bit before deref in case the cm_id gets freed on another
* thread.
*/
cb_destroy = test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
if (iwcm_deref_id(cm_id_priv) && cb_destroy) {
BUG_ON(!list_empty(&cm_id_priv->work_list));
free_cm_id(cm_id_priv);
}
(void)iwcm_deref_id(cm_id_priv);
}
static int cm_event_handler(struct iw_cm_id *cm_id, struct iw_cm_event *event);
@ -370,6 +360,12 @@ static void destroy_cm_id(struct iw_cm_id *cm_id)
wait_event(cm_id_priv->connect_wait,
!test_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags));
/*
* Since we're deleting the cm_id, drop any events that
* might arrive before the last dereference.
*/
set_bit(IWCM_F_DROP_EVENTS, &cm_id_priv->flags);
spin_lock_irqsave(&cm_id_priv->lock, flags);
switch (cm_id_priv->state) {
case IW_CM_STATE_LISTEN:
@ -433,13 +429,7 @@ void iw_destroy_cm_id(struct iw_cm_id *cm_id)
struct iwcm_id_private *cm_id_priv;
cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
BUG_ON(test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags));
destroy_cm_id(cm_id);
wait_for_completion(&cm_id_priv->destroy_comp);
free_cm_id(cm_id_priv);
}
EXPORT_SYMBOL(iw_destroy_cm_id);
@ -809,10 +799,7 @@ static void cm_conn_req_handler(struct iwcm_id_private *listen_id_priv,
ret = cm_id->cm_handler(cm_id, iw_event);
if (ret) {
iw_cm_reject(cm_id, NULL, 0);
set_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
destroy_cm_id(cm_id);
if (atomic_read(&cm_id_priv->refcount)==0)
free_cm_id(cm_id_priv);
iw_destroy_cm_id(cm_id);
}
out:
@ -1000,7 +987,6 @@ static void cm_work_handler(struct work_struct *_work)
unsigned long flags;
int empty;
int ret = 0;
int destroy_id;
spin_lock_irqsave(&cm_id_priv->lock, flags);
empty = list_empty(&cm_id_priv->work_list);
@ -1013,20 +999,14 @@ static void cm_work_handler(struct work_struct *_work)
put_work(work);
spin_unlock_irqrestore(&cm_id_priv->lock, flags);
if (!test_bit(IWCM_F_DROP_EVENTS, &cm_id_priv->flags)) {
ret = process_event(cm_id_priv, &levent);
if (ret) {
set_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
if (ret)
destroy_cm_id(&cm_id_priv->id);
}
BUG_ON(atomic_read(&cm_id_priv->refcount)==0);
destroy_id = test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
if (iwcm_deref_id(cm_id_priv)) {
if (destroy_id) {
BUG_ON(!list_empty(&cm_id_priv->work_list));
free_cm_id(cm_id_priv);
}
} else
pr_debug("dropping event %d\n", levent.event);
if (iwcm_deref_id(cm_id_priv))
return;
}
if (empty)
return;
spin_lock_irqsave(&cm_id_priv->lock, flags);

2
drivers/infiniband/core/iwcm.h
View File

@ -56,7 +56,7 @@ struct iwcm_id_private {
struct list_head work_free_list;
};
#define IWCM_F_CALLBACK_DESTROY 1
#define IWCM_F_DROP_EVENTS 1
#define IWCM_F_CONNECT_WAIT 2
#endif /* IWCM_H */