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uGNI: Fix potential deadlock when processing outstanding transfers (v4.0.x) #7180

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merged 1 commit into from
Nov 20, 2019
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uGNI: Fix potential deadlock when processing outstanding transfers (v4.0.x) #7180

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30 changes: 21 additions & 9 deletions opal/mca/btl/ugni/btl_ugni_component.c
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Original file line number Diff line number Diff line change
Expand Up @@ -664,34 +664,46 @@ static inline int
mca_btl_ugni_progress_wait_list (mca_btl_ugni_module_t *ugni_module)
{
int rc = OPAL_SUCCESS;
opal_list_t tmplist;
opal_list_t *waitlist = &ugni_module->ep_wait_list;
mca_btl_base_endpoint_t *endpoint = NULL;
int count;

if (0 == opal_list_get_size(&ugni_module->ep_wait_list)) {
return 0;
}

/* check the count before taking the lock to avoid unnecessary locking */
count = opal_list_get_size(&ugni_module->ep_wait_list);
count = opal_list_get_size(waitlist);
if (0 == count) {
return 0;
}

/* Don't hold the wait-list lock while processing the list as that may lead
* to a deadlock.
* Instead, move the wait_list elements into a temporary list and work on that.*/
OBJ_CONSTRUCT(&tmplist, opal_list_t);
OPAL_THREAD_LOCK(&ugni_module->ep_wait_list_lock);
count = opal_list_get_size(&ugni_module->ep_wait_list);
opal_list_join(&tmplist, opal_list_get_end(&tmplist), waitlist);
OPAL_THREAD_UNLOCK(&ugni_module->ep_wait_list_lock);
count = opal_list_get_size(&tmplist);
do {
endpoint = (mca_btl_base_endpoint_t *) opal_list_remove_first (&ugni_module->ep_wait_list);
endpoint = (mca_btl_base_endpoint_t *) opal_list_remove_first (&tmplist);
if (endpoint != NULL) {
rc = mca_btl_ugni_progress_send_wait_list (endpoint);

if (OPAL_SUCCESS != rc) {
opal_list_append (&ugni_module->ep_wait_list, &endpoint->super);
opal_list_append (&tmplist, &endpoint->super);
} else {
endpoint->wait_listed = false;
}
}
} while (endpoint != NULL && --count > 0) ;
OPAL_THREAD_UNLOCK(&ugni_module->ep_wait_list_lock);

/* reinsert unfinished elements into the wait-list */
count = opal_list_get_size(&tmplist);
if (0 < count) {
OPAL_THREAD_LOCK(&ugni_module->ep_wait_list_lock);
opal_list_join(waitlist, opal_list_get_end(waitlist), &tmplist);
OPAL_THREAD_UNLOCK(&ugni_module->ep_wait_list_lock);
}
OBJ_DESTRUCT(&tmplist);

return rc;
}
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