firewire: sbp2: protect a reference counter properly (0765cbd3) · Commits · 戴 / test

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:

Stefan Richter <stefanr@s5r6.in-berlin.de>

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);
		}

		/*

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