This patch adds reference counting for ACPI IPMI transfers to tune the
locking granularity of tx_msg_lock.
This patch also makes the whole acpi_ipmi module's coding style consistent
by using reference counting for all its objects (i.e., acpi_ipmi_device and
acpi_ipmi_msg).
The acpi_ipmi_msg handling is re-designed using referece counting.
1. tx_msg is always unlinked before complete(), so that it is safe to put
complete() out side of tx_msg_lock.
2. tx_msg reference counters are incremented before calling
ipmi_request_settime() and tx_msg_lock protection is added to
ipmi_cancel_tx_msg() so that a complete() can be safely called in
parellel with tx_msg unlinking in failure cases.
3. tx_msg holds a reference to acpi_ipmi_device so that it can be flushed
and freed in the contexts other than acpi_ipmi_space_handler().
The lockdep_chains shows all acpi_ipmi locks are leaf locks after the
tuning:
1. ipmi_lock is always leaf:
irq_context: 0
[ffffffff81a943f8] smi_watchers_mutex
[ffffffffa06eca60] driver_data.ipmi_lock
irq_context: 0
[ffffffff82767b40] &buffer->mutex
[ffffffffa00a6678] s_active#103
[ffffffffa06eca60] driver_data.ipmi_lock
2. without this patch applied, lock used by complete() is held after
holding tx_msg_lock:
irq_context: 0
[ffffffff82767b40] &buffer->mutex
[ffffffffa00a6678] s_active#103
[ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
irq_context: 1
[ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
irq_context: 1
[ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
[ffffffffa06eccf0] &x->wait#25
irq_context: 1
[ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
[ffffffffa06eccf0] &x->wait#25
[ffffffff81e36620] &p->pi_lock
irq_context: 1
[ffffffffa06ecce8] &(&ipmi_device->tx_msg_lock)->rlock
[ffffffffa06eccf0] &x->wait#25
[ffffffff81e36620] &p->pi_lock
[ffffffff81e5d0a8] &rq->lock
3. with this patch applied, tx_msg_lock is always leaf:
irq_context: 0
[ffffffff82767b40] &buffer->mutex
[ffffffffa00a66d8] s_active#107
[ffffffffa07ecdc8] &(&ipmi_device->tx_msg_lock)->rlock
irq_context: 1
[ffffffffa07ecdc8] &(&ipmi_device->tx_msg_lock)->rlock
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reviewed-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
7b98447722