[PATCH v1] mpt3sas: correct reset of smid while clearing scsi tracker

[Sreekanth Reddy]

In mpt3sas_base_clear_st() function smid value is reseted in wrong line,
i.e. driver should reset smid value to zero after decrementing chain_offset
counter in chain_lookup table but in current code, driver is resetting smid
value before decrementing the chain_offset counter. which we are correcting
with this patch.

v1 changelog:
Added memory barriers before & after atomic_set() API.

Signed-off-by: Sreekanth Reddy <sreekanth.re...@broadcom.com>
---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c 
b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 902610d..94359d8 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -1702,6 +1702,8 @@ static int mpt3sas_remove_dead_ioc_func(void *arg)
                return NULL;
 
        chain_req = &ioc->chain_lookup[smid - 1].chains_per_smid[chain_offset];
+       /* Adding memory barrier before atomic operation. */
+       smp_mb__before_atomic();
        atomic_inc(&ioc->chain_lookup[smid - 1].chain_offset);
        return chain_req;
 }
@@ -3283,8 +3285,12 @@ void mpt3sas_base_clear_st(struct MPT3SAS_ADAPTER *ioc,
                return;
        st->cb_idx = 0xFF;
        st->direct_io = 0;
-       st->smid = 0;
+       /* Adding memory barrier before atomic operation. */
+       smp_mb__before_atomic();
        atomic_set(&ioc->chain_lookup[st->smid - 1].chain_offset, 0);
+       /* Adding memory barrier after atomic operation. */
+       smp_mb__after_atomic();
+       st->smid = 0;
 }
 
 /**
-- 
1.8.3.1