[CCID 3]: Reduce time spent while write-lock is held
This minimizes the time during which the `write_lock' is held: by using a
temporary list_head and re-adjusting the pointers of the old list accordingly.
The clean-up operation can then safely be done outside the lock, since the
newly created list is then `homeless'.
1. For dccp_tx_hist_purge, this is conveniently done by using list_replace_init,
2. the case for dccp_tx_hist_purge_older is analogous and, in the absence of a
matching library function, done manually;
3. the `dangerous' function dccp_tx_hist_purge_older has been removed by
merging its functionality into dccp_tx_hist_get_send_time.
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/ccids/lib/packet_history.c | 47 +++++++++++++++++++-----------------
net/dccp/ccids/lib/packet_history.h | 4 ---
2 files changed, 25 insertions(+), 26 deletions(-)
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -87,6 +87,16 @@ void dccp_tx_hist_delete(struct dccp_tx_
EXPORT_SYMBOL_GPL(dccp_tx_hist_delete);
+static void __dccp_tx_hist_wipe(struct list_head *head, struct kmem_cache *slab)
+{
+ struct dccp_tx_hist_entry *entry, *next;
+
+ list_for_each_entry_safe(entry, next, head, dccphtx_node) {
+ list_del(&entry->dccphtx_node);
+ kmem_cache_free(slab, entry);
+ }
+}
+
/**
* dccp_tx_hist_get_send_time - Retrieve timestamp of sent packet
*
@@ -101,6 +111,7 @@ int dccp_tx_hist_get_send_time(struct dc
struct timeval *t_send)
{
struct dccp_tx_hist_entry *entry;
+ struct list_head free_this;
int found = 0;
write_lock_bh(&dccp_tx_hist_lock);
@@ -108,12 +119,20 @@ int dccp_tx_hist_get_send_time(struct dc
if (entry->dccphtx_seqno == seq) {
found = 1;
*t_send = entry->dccphtx_tstamp;
+ /* forget/free all entries older than this one */
+ free_this.next = entry->dccphtx_node.next;
+ free_this.next->prev = &free_this;
+ free_this.prev = list->prev;
+ free_this.prev->next = &free_this;
+
+ entry->dccphtx_node.next = list;
+ list->prev = &entry->dccphtx_node;
break;
}
+ write_unlock_bh(&dccp_tx_hist_lock);
if (found)
- dccp_tx_hist_purge_older(hist, list, entry);
- write_unlock_bh(&dccp_tx_hist_lock);
+ __dccp_tx_hist_wipe(&free_this, hist->dccptxh_slab);
return found;
}
@@ -132,32 +151,16 @@ EXPORT_SYMBOL_GPL(dccp_tx_hist_add_entry
void dccp_tx_hist_purge(struct dccp_tx_hist *hist, struct list_head *list)
{
- struct dccp_tx_hist_entry *entry, *next;
+ struct list_head free_this;
write_lock_bh(&dccp_tx_hist_lock);
- list_for_each_entry_safe(entry, next, list, dccphtx_node) {
- list_del_init(&entry->dccphtx_node);
- dccp_tx_hist_entry_delete(hist, entry);
- }
+ list_replace_init(list, &free_this);
write_unlock_bh(&dccp_tx_hist_lock);
-}
-EXPORT_SYMBOL_GPL(dccp_tx_hist_purge);
-
-/* XXX careful, this one is not lock-protected */
-void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist,
- struct list_head *list,
- struct dccp_tx_hist_entry *packet)
-{
- struct dccp_tx_hist_entry *next;
-
- list_for_each_entry_safe_continue(packet, next, list, dccphtx_node) {
- list_del_init(&packet->dccphtx_node);
- dccp_tx_hist_entry_delete(hist, packet);
- }
+ __dccp_tx_hist_wipe(&free_this, hist->dccptxh_slab);
}
-EXPORT_SYMBOL_GPL(dccp_tx_hist_purge_older);
+EXPORT_SYMBOL_GPL(dccp_tx_hist_purge);
/*
* Receiver History Routines
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -95,10 +95,6 @@ static inline void dccp_tx_hist_entry_de
extern void dccp_tx_hist_purge(struct dccp_tx_hist *hist,
struct list_head *list);
-extern void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist,
- struct list_head *list,
- struct dccp_tx_hist_entry *next);
-
/*
* Receiver History data structures and declarations
*/
-
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