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greybus: protocol: warn on bad deregistration

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A protocol should be deregistered exactly once when the protocol module
is being unloaded. This means that protocol deregister will never be
called with active users as we take a module reference when looking up a
protocol.

Remove comment suggesting that we could one day forcefully stop a user
of a protocol, and issue a big warning if a protocol is deregistered
more than once or at some other time than during module unload (e.g.
with active users).

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Johan Hovold 2015-10-13 19:10:24 +02:00 committed by Greg Kroah-Hartman
parent 0b1118a9ef
commit 78033844da
2 changed files with 9 additions and 21 deletions
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28
drivers/staging/greybus/protocol.c
View File

@ -102,36 +102,24 @@ EXPORT_SYMBOL_GPL(__gb_protocol_register);
/*
* De-register a previously registered protocol.
*
* XXX Currently this fails (and reports an error to the caller) if
* XXX the protocol is currently in use. We may want to forcefully
* XXX kill off a protocol and all its active users at some point.
* XXX But I think that's better handled by quiescing modules that
* XXX have users and having those users drop their reference.
*
* Returns true if successful, false otherwise.
*/
int gb_protocol_deregister(struct gb_protocol *protocol)
void gb_protocol_deregister(struct gb_protocol *protocol)
{
u8 protocol_count = 0;
if (!protocol)
return 0;
return;
spin_lock_irq(&gb_protocols_lock);
protocol = gb_protocol_find(protocol->id, protocol->major,
protocol->minor);
if (protocol) {
protocol_count = protocol->count;
if (!protocol_count)
list_del(&protocol->links);
if (WARN_ON(!protocol || protocol->count)) {
spin_unlock_irq(&gb_protocols_lock);
return;
}
list_del(&protocol->links);
spin_unlock_irq(&gb_protocols_lock);
if (protocol)
pr_info("Deregistered %s protocol.\n", protocol->name);
return protocol && !protocol_count;
pr_info("Deregistered %s protocol.\n", protocol->name);
}
EXPORT_SYMBOL_GPL(gb_protocol_deregister);

2
drivers/staging/greybus/protocol.h
View File

@ -46,7 +46,7 @@ struct gb_protocol {
};
int __gb_protocol_register(struct gb_protocol *protocol, struct module *module);
int gb_protocol_deregister(struct gb_protocol *protocol);
void gb_protocol_deregister(struct gb_protocol *protocol);
#define gb_protocol_register(protocol) \
__gb_protocol_register(protocol, THIS_MODULE)