[net-next 15/15] i40e: synchronize nvmupdate command and adminq subtask

[Jeff Kirsher]

From: Sudheer Mogilappagari <sudheer.mogilappag...@intel.com>

During NVM update, state machine gets into unrecoverable state because
i40e_clean_adminq_subtask can get scheduled after the admin queue
command but before other state variables are updated. This causes
incorrect input to i40e_nvmupd_check_wait_event and state transitions
don't happen.

This issue existed before but surfaced after commit 373149fc99a0
("i40e: Decrease the scope of rtnl lock")

This fix adds locking around admin queue command and update of
state variables so that adminq_subtask will have accurate information
whenever it gets scheduled.

Signed-off-by: Sudheer Mogilappagari <sudheer.mogilappag...@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
---
 drivers/net/ethernet/intel/i40e/i40e_nvm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_nvm.c 
b/drivers/net/ethernet/intel/i40e/i40e_nvm.c
index 6fdecd70dcbc..2cf7db2dc7cd 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_nvm.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_nvm.c
@@ -753,6 +753,11 @@ i40e_status i40e_nvmupd_command(struct i40e_hw *hw,
                hw->nvmupd_state = I40E_NVMUPD_STATE_INIT;
        }
 
+       /* Acquire lock to prevent race condition where adminq_task
+        * can execute after i40e_nvmupd_nvm_read/write but before state
+        * variables (nvm_wait_opcode, nvm_release_on_done) are updated
+        */
+       mutex_lock(&hw->aq.arq_mutex);
        switch (hw->nvmupd_state) {
        case I40E_NVMUPD_STATE_INIT:
                status = i40e_nvmupd_state_init(hw, cmd, bytes, perrno);
@@ -788,6 +793,7 @@ i40e_status i40e_nvmupd_command(struct i40e_hw *hw,
                *perrno = -ESRCH;
                break;
        }
+       mutex_unlock(&hw->aq.arq_mutex);
        return status;
 }
 
-- 
2.14.0