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author | Joern Engel <joern@logfs.org> | 2014-09-16 16:23:12 -0400 |
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committer | Nicholas Bellinger <nab@linux-iscsi.org> | 2014-10-01 14:39:06 -0700 |
commit | 33940d09937276cd3c81f2874faf43e37c2db0e2 (patch) | |
tree | 2c3043e6902ee4e8e23b947f2e30e50967e99c5b /drivers/target/target_core_transport.c | |
parent | 74ed7e62289dc6d388996d7c8f89c2e7e95b9657 (diff) | |
download | op-kernel-dev-33940d09937276cd3c81f2874faf43e37c2db0e2.zip op-kernel-dev-33940d09937276cd3c81f2874faf43e37c2db0e2.tar.gz |
target: encapsulate smp_mb__after_atomic()
The target code has a rather generous helping of smp_mb__after_atomic()
throughout the code base. Most atomic operations were followed by one
and none were preceded by smp_mb__before_atomic(), nor accompanied by a
comment explaining the need for a barrier.
Instead of trying to prove for every case whether or not it is needed,
this patch introduces atomic_inc_mb() and atomic_dec_mb(), which
explicitly include the memory barriers before and after the atomic
operation. For now they are defined in a target header, although they
could be of general use.
Most of the existing atomic/mb combinations were replaced by the new
helpers. In a few cases the atomic was sandwiched in
spin_lock/spin_unlock and I simply removed the barrier.
I suspect that in most cases the correct conversion would have been to
drop the barrier. I also suspect that a few cases exist where a) the
barrier was necessary and b) a second barrier before the atomic would
have been necessary and got added by this patch.
Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers/target/target_core_transport.c')
-rw-r--r-- | drivers/target/target_core_transport.c | 18 |
1 files changed, 6 insertions, 12 deletions
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index 0b43761..115632e 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -752,8 +752,7 @@ void target_qf_do_work(struct work_struct *work) list_for_each_entry_safe(cmd, cmd_tmp, &qf_cmd_list, se_qf_node) { list_del(&cmd->se_qf_node); - atomic_dec(&dev->dev_qf_count); - smp_mb__after_atomic(); + atomic_dec_mb(&dev->dev_qf_count); pr_debug("Processing %s cmd: %p QUEUE_FULL in work queue" " context: %s\n", cmd->se_tfo->get_fabric_name(), cmd, @@ -1721,8 +1720,7 @@ static bool target_handle_task_attr(struct se_cmd *cmd) cmd->t_task_cdb[0], cmd->se_ordered_id); return false; case MSG_ORDERED_TAG: - atomic_inc(&dev->dev_ordered_sync); - smp_mb__after_atomic(); + atomic_inc_mb(&dev->dev_ordered_sync); pr_debug("Added ORDERED for CDB: 0x%02x to ordered list, " " se_ordered_id: %u\n", @@ -1739,8 +1737,7 @@ static bool target_handle_task_attr(struct se_cmd *cmd) /* * For SIMPLE and UNTAGGED Task Attribute commands */ - atomic_inc(&dev->simple_cmds); - smp_mb__after_atomic(); + atomic_inc_mb(&dev->simple_cmds); break; } @@ -1844,8 +1841,7 @@ static void transport_complete_task_attr(struct se_cmd *cmd) return; if (cmd->sam_task_attr == MSG_SIMPLE_TAG) { - atomic_dec(&dev->simple_cmds); - smp_mb__after_atomic(); + atomic_dec_mb(&dev->simple_cmds); dev->dev_cur_ordered_id++; pr_debug("Incremented dev->dev_cur_ordered_id: %u for" " SIMPLE: %u\n", dev->dev_cur_ordered_id, @@ -1856,8 +1852,7 @@ static void transport_complete_task_attr(struct se_cmd *cmd) " HEAD_OF_QUEUE: %u\n", dev->dev_cur_ordered_id, cmd->se_ordered_id); } else if (cmd->sam_task_attr == MSG_ORDERED_TAG) { - atomic_dec(&dev->dev_ordered_sync); - smp_mb__after_atomic(); + atomic_dec_mb(&dev->dev_ordered_sync); dev->dev_cur_ordered_id++; pr_debug("Incremented dev_cur_ordered_id: %u for ORDERED:" @@ -1915,8 +1910,7 @@ static void transport_handle_queue_full( { spin_lock_irq(&dev->qf_cmd_lock); list_add_tail(&cmd->se_qf_node, &cmd->se_dev->qf_cmd_list); - atomic_inc(&dev->dev_qf_count); - smp_mb__after_atomic(); + atomic_inc_mb(&dev->dev_qf_count); spin_unlock_irq(&cmd->se_dev->qf_cmd_lock); schedule_work(&cmd->se_dev->qf_work_queue); |