Date: Sun, 19 Aug 2012 02:50:02 -0400 From: Peter Hurley <[email protected]>
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 are now no longer serialized. (There is still per-card serialization 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 <[email protected]> Signed-off-by: Stefan Richter <[email protected]> --- Peter, are you OK with the new changelog? drivers/firewire/core-transaction.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) --- a/drivers/firewire/core-transaction.c +++ b/drivers/firewire/core-transaction.c @@ -489,7 +489,7 @@ static struct fw_address_handler *lookup { 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 +510,7 @@ static struct fw_address_handler *lookup { 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 +588,7 @@ int fw_core_add_address_handler(struct f 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 +609,9 @@ EXPORT_SYMBOL(fw_core_add_address_handle 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 +845,7 @@ static void handle_exclusive_region_requ 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 +854,7 @@ static void handle_exclusive_region_requ 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 +887,8 @@ static void handle_fcp_region_request(st 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 +897,7 @@ static void handle_fcp_region_request(st request->length, handler->callback_data); } - spin_unlock_bh(&address_handler_lock); + rcu_read_unlock(); fw_send_response(card, request, RCODE_COMPLETE); } -- Stefan Richter -=====-===-- =--= ==-== http://arcgraph.de/sr/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
