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Commit 4d50c443 authored by Stefan Richter's avatar Stefan Richter
Browse files

firewire: addendum to address handler RCU conversion 



Follow up on commit c285f6ff6787 "firewire: remove global lock around
address handlers, convert to RCU":

  - address_handler_lock no longer serializes the address handler, only
    its function to serialize updates to the list of handlers remains.
    Rename the lock to address_handler_list_lock.

  - Callers of fw_core_remove_address_handler() must be able to sleep.
    Comment on this in the API documentation.

  - The counterpart fw_core_add_address_handler() is by nature something
    which is used in process context.  Replace spin_lock_bh() by
    spin_lock() in fw_core_add_address_handler() and in
    fw_core_remove_address_handler(), and document that process context
    is now required for fw_core_add_address_handler().

  - Extend the documentation of fw_address_callback_t.

Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent 35202f7d

drivers/firewire/core-transaction.c

+8 −5
Original line number Diff line number Diff line
@@ -519,7 +519,7 @@ static struct fw_address_handler *lookup_enclosing_address_handler( 
	return NULL;

}



static DEFINE_SPINLOCK(address_handler_lock);

static DEFINE_SPINLOCK(address_handler_list_lock);

static LIST_HEAD(address_handler_list);



const struct fw_address_region fw_high_memory_region =
@@ -556,6 +556,7 @@ static bool is_in_fcp_region(u64 offset, size_t length) 
 * the specified callback is invoked.  The parameters passed to the callback

 * give the details of the particular request.

 *

 * To be called in process context.

 * Return value:  0 on success, non-zero otherwise.

 *

 * The start offset of the handler's address region is determined by
@@ -576,7 +577,7 @@ int fw_core_add_address_handler(struct fw_address_handler *handler, 
	    handler->length == 0)

		return -EINVAL;



	spin_lock_bh(&address_handler_lock);

	spin_lock(&address_handler_list_lock);



	handler->offset = region->start;

	while (handler->offset + handler->length <= region->end) {
@@ -595,7 +596,7 @@ int fw_core_add_address_handler(struct fw_address_handler *handler, 
		}

	}



	spin_unlock_bh(&address_handler_lock);

	spin_unlock(&address_handler_list_lock);



	return ret;

}
@@ -604,14 +605,16 @@ EXPORT_SYMBOL(fw_core_add_address_handler); 
/**

 * fw_core_remove_address_handler() - unregister an address handler

 *

 * To be called in process context.

 *

 * When fw_core_remove_address_handler() returns, @handler->callback() is

 * guaranteed to not run on any CPU anymore.

 */

void fw_core_remove_address_handler(struct fw_address_handler *handler)

{

	spin_lock_bh(&address_handler_lock);

	spin_lock(&address_handler_list_lock);

	list_del_rcu(&handler->link);

	spin_unlock_bh(&address_handler_lock);

	spin_unlock(&address_handler_list_lock);

	synchronize_rcu();

}

EXPORT_SYMBOL(fw_core_remove_address_handler);

include/linux/firewire.h

+10 −2
Original line number Diff line number Diff line
@@ -265,8 +265,16 @@ typedef void (*fw_transaction_callback_t)(struct fw_card *card, int rcode, 
					  void *data, size_t length,

					  void *callback_data);

/*

 * Important note:  Except for the FCP registers, the callback must guarantee

 * that either fw_send_response() or kfree() is called on the @request.

 * This callback handles an inbound request subaction.  It is called in

 * RCU read-side context, therefore must not sleep.

 *

 * The callback should not initiate outbound request subactions directly.

 * Otherwise there is a danger of recursion of inbound and outbound

 * transactions from and to the local node.

 *

 * The callback is responsible that either fw_send_response() or kfree()

 * is called on the @request, except for FCP registers for which the core

 * takes care of that.

 */

typedef void (*fw_address_callback_t)(struct fw_card *card,

				      struct fw_request *request,