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SubjectRe: [PATCH] ieee1394: sbp2: fix race condition in state change
I wrote:
> An intermediate transition from _RUNNING to _IN_SHUTDOWN could have been
> missed by the former code.
>
> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
> ---
> drivers/ieee1394/sbp2.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> Index: linux/drivers/ieee1394/sbp2.c
> ===================================================================
> --- linux.orig/drivers/ieee1394/sbp2.c
> +++ linux/drivers/ieee1394/sbp2.c
> @@ -895,12 +895,13 @@ static void sbp2_host_reset(struct hpsb_
> return;
>
> read_lock_irqsave(&sbp2_hi_logical_units_lock, flags);
> +
> list_for_each_entry(lu, &hi->logical_units, lu_list)
> - if (likely(atomic_read(&lu->state) !=
> - SBP2LU_STATE_IN_SHUTDOWN)) {
> - atomic_set(&lu->state, SBP2LU_STATE_IN_RESET);
> + if (atomic_cmpxchg(&lu->state,
> + SBP2LU_STATE_RUNNING, SBP2LU_STATE_IN_RESET)
> + == SBP2LU_STATE_RUNNING)
> scsi_block_requests(lu->shost);
> - }
> +
> read_unlock_irqrestore(&sbp2_hi_logical_units_lock, flags);
> }
>

Still not entirely correct. Maybe

scsi_block_requests(lu->shost);
if (atomic_cmpxchg(&lu->state,
SBP2LU_STATE_RUNNING,
SBP2LU_STATE_IN_RESET)
== SBP2LU_IN_SHUTDOWN)
scsi_unblock_requests(lu->shost);

Does What I Mean. Or I should just put a lock around all lu->state and
shost->host_self_blocked manipulations.
--
Stefan Richter
-=====-==--- ==-- ----=
http://arcgraph.de/sr/


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