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authorPeter Hurley <peter@hurleysoftware.com>2012-08-19 02:50:02 -0400
committerStefan Richter <stefanr@s5r6.in-berlin.de>2012-09-28 11:47:41 +0200
commit35202f7d8420fff586b372422a2419affeaba8ef (patch)
tree617a3f8c13fa06e46432029ad172c172db8d4dd3 /drivers/firewire
parent52439d605d6604c15954281a1d2831471dbd024c (diff)
downloadlinux-35202f7d8420fff586b372422a2419affeaba8ef.tar.gz
firewire: remove global lock around address handlers, convert to RCU
Upper-layer handlers for inbound requests were called with a spinlock held by firewire-core. Calling into upper layers with a lower layer lock held is generally a bad idea. What's more, since commit ea102d0ec475 "firewire: core: convert AR-req handler lock from _irqsave to _bh", a caller of fw_send_request() i.e. initiator of outbound request could no longer do that while having interrupts disabled, if the local node was addressed by that request. In order to make all this more flexible, convert the management of address ranges and handlers from a global lock around readers and writers to RCU (and a remaining global lock for writers). As a minor side effect, handling of inbound requests at different cards and of local requests is now no longer serialized. (There is still per-card serialization of remote requests since firewire-ohci uses a single DMA tasklet for inbound request events.) In other words, address handlers are now called in an RCU read-side critical section instead of from within a spin_lock_bh serialized section. (Changelog rewritten by Stefan R.) Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Diffstat (limited to 'drivers/firewire')
-rw-r--r--drivers/firewire/core-transaction.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index 87d6f2d2f02..d39cfa45817 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -31,6 +31,7 @@
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
+#include <linux/rculist.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
@@ -489,7 +490,7 @@ static struct fw_address_handler *lookup_overlapping_address_handler(
{
struct fw_address_handler *handler;
- list_for_each_entry(handler, list, link) {
+ list_for_each_entry_rcu(handler, list, link) {
if (handler->offset < offset + length &&
offset < handler->offset + handler->length)
return handler;
@@ -510,7 +511,7 @@ static struct fw_address_handler *lookup_enclosing_address_handler(
{
struct fw_address_handler *handler;
- list_for_each_entry(handler, list, link) {
+ list_for_each_entry_rcu(handler, list, link) {
if (is_enclosing_handler(handler, offset, length))
return handler;
}
@@ -588,7 +589,7 @@ int fw_core_add_address_handler(struct fw_address_handler *handler,
if (other != NULL) {
handler->offset += other->length;
} else {
- list_add_tail(&handler->link, &address_handler_list);
+ list_add_tail_rcu(&handler->link, &address_handler_list);
ret = 0;
break;
}
@@ -609,8 +610,9 @@ EXPORT_SYMBOL(fw_core_add_address_handler);
void fw_core_remove_address_handler(struct fw_address_handler *handler)
{
spin_lock_bh(&address_handler_lock);
- list_del(&handler->link);
+ list_del_rcu(&handler->link);
spin_unlock_bh(&address_handler_lock);
+ synchronize_rcu();
}
EXPORT_SYMBOL(fw_core_remove_address_handler);
@@ -844,7 +846,7 @@ static void handle_exclusive_region_request(struct fw_card *card,
if (tcode == TCODE_LOCK_REQUEST)
tcode = 0x10 + HEADER_GET_EXTENDED_TCODE(p->header[3]);
- spin_lock_bh(&address_handler_lock);
+ rcu_read_lock();
handler = lookup_enclosing_address_handler(&address_handler_list,
offset, request->length);
if (handler)
@@ -853,7 +855,7 @@ static void handle_exclusive_region_request(struct fw_card *card,
p->generation, offset,
request->data, request->length,
handler->callback_data);
- spin_unlock_bh(&address_handler_lock);
+ rcu_read_unlock();
if (!handler)
fw_send_response(card, request, RCODE_ADDRESS_ERROR);
@@ -886,8 +888,8 @@ static void handle_fcp_region_request(struct fw_card *card,
return;
}
- spin_lock_bh(&address_handler_lock);
- list_for_each_entry(handler, &address_handler_list, link) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(handler, &address_handler_list, link) {
if (is_enclosing_handler(handler, offset, request->length))
handler->address_callback(card, NULL, tcode,
destination, source,
@@ -896,7 +898,7 @@ static void handle_fcp_region_request(struct fw_card *card,
request->length,
handler->callback_data);
}
- spin_unlock_bh(&address_handler_lock);
+ rcu_read_unlock();
fw_send_response(card, request, RCODE_COMPLETE);
}