ACPI / IPMI: Add reference counting for ACPI IPMI transfers
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: NLv Zheng <lv.zheng@intel.com> Reviewed-by: NHuang Ying <ying.huang@intel.com> Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
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