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Commit 0765cbd3 authored by Stefan Richter's avatar Stefan Richter
Browse files

firewire: sbp2: protect a reference counter properly 



The assertion in the comment in sbp2_allow_block() is no longer true.
Or maybe it never was true.  At least now, the sole caller of
sbp2_allow_block(), sbp2_login, can run concurrently to one of
sbp2_unblock()'s callers, sbp2_remove.

sbp2_login is performed by sbp2_logical_unit.work.
sbp2_remove is performed by fw_device.work.
sbp2_remove cancels sbp2_logical_unit.work, but only after it called
sbp2_unblock.

Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent 0238507b

drivers/firewire/sbp2.c

+6 −8
Original line number Diff line number Diff line
@@ -689,14 +689,12 @@ static void sbp2_agent_reset_no_wait(struct sbp2_logical_unit *lu) 


static inline void sbp2_allow_block(struct sbp2_logical_unit *lu)

{

	/*

	 * We may access dont_block without taking card->lock here:

	 * All callers of sbp2_allow_block() and all callers of sbp2_unblock()

	 * are currently serialized against each other.

	 * And a wrong result in sbp2_conditionally_block()'s access of

	 * dont_block is rather harmless, it simply misses its first chance.

	 */

	--lu->tgt->dont_block;

	struct sbp2_target *tgt = lu->tgt;

	struct fw_card *card = target_parent_device(tgt)->card;



	spin_lock_irq(&card->lock);

	--tgt->dont_block;

	spin_unlock_irq(&card->lock);

}



/*