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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: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter 2014-03-03 23:22:35 +01:00
parent 0238507b95
commit 0765cbd3be
1 changed files with 6 additions and 8 deletions
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14
drivers/firewire/sbp2.c
View File

@ -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);
}
/*