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server: improve callback list and safeguard locking 

Coding style: pairwise nesting of lock/unlock.

Always prefer writes in front of reads when callbacks
need to be transported.
This commit is contained in:
Thomas Schoebel-Theuer 2022-06-01 10:47:04 +02:00 committed by Thomas Schoebel-Theuer
parent d901c41793
commit 5a659a0441
1 changed files with 25 additions and 9 deletions
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34
kernel/mars_server.c
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@ -123,20 +123,36 @@ int cb_thread(void *data)
!list_empty(&brick->cb_write_list),
1 * HZ);
/* Try to get the next request for callback over
* the network.
* Writes are preferred.
* This is important for long-distance transports
* of IO (e.g. using MARS for iSCSI-like use cases).
* Use the cork iff there are some more requests
* to be completed, whether reads or writes.
*/
tmp = NULL;
cork = false;
mutex_lock(&brick->cb_mutex);
tmp = brick->cb_write_list.next;
if (tmp == &brick->cb_write_list) {
if (!list_empty(&brick->cb_write_list)) {
tmp = brick->cb_write_list.next;
list_del_init(tmp);
cork =
!list_empty(&brick->cb_write_list) ||
!list_empty(&brick->cb_read_list);
} else if (!list_empty(&brick->cb_read_list)) {
tmp = brick->cb_read_list.next;
if (tmp == &brick->cb_read_list) {
mutex_unlock(&brick->cb_mutex);
brick_yield();
continue;
}
list_del_init(tmp);
cork = !list_empty(&brick->cb_read_list);
}
list_del_init(tmp);
cork = !list_empty(&brick->cb_write_list);
mutex_unlock(&brick->cb_mutex);
if (!tmp) {
/* nothing to do for now */
brick_yield();
continue;
}
mref_a = container_of(tmp, struct server_mref_aspect, cb_head);
mref = mref_a->object;
status = -EINVAL;