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firewire: addendum to address handler RCU conversion

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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: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter 2012-09-27 21:46:09 +02:00
parent 35202f7d84
commit 4d50c44381
2 changed files with 18 additions and 7 deletions
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13
drivers/firewire/core-transaction.c
View File

@ -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);

12
include/linux/firewire.h
View File

@ -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,