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author | Bart Van Assche <bart.vanassche@wdc.com> | 2018-06-22 14:52:54 -0700 |
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committer | Martin K. Petersen <martin.petersen@oracle.com> | 2018-07-02 16:44:31 -0400 |
commit | 953bcf7ad16ac6ecee7d2f5593501aee5e5ae8b8 (patch) | |
tree | 001bcd757513994a3ac483d565c78bef8dbe7e05 /drivers/target/target_core_transport.c | |
parent | 00d909a10710a3416272d4179adf3837b9a9f3c2 (diff) | |
download | linux-stable-953bcf7ad16ac6ecee7d2f5593501aee5e5ae8b8.tar.gz linux-stable-953bcf7ad16ac6ecee7d2f5593501aee5e5ae8b8.tar.bz2 linux-stable-953bcf7ad16ac6ecee7d2f5593501aee5e5ae8b8.zip |
scsi: target: Document when CMD_T_STOP and CMD_T_COMPLETE are set
Document those aspects of transport_cmd_check_stop_to_fabric() and
transport_generic_free_cmd() of which it is nontrivial to derive these from
their implementation.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/target/target_core_transport.c')
-rw-r--r-- | drivers/target/target_core_transport.c | 34 |
1 files changed, 28 insertions, 6 deletions
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index 087dddfc5c35..47318f64296d 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -632,6 +632,13 @@ static void target_remove_from_state_list(struct se_cmd *cmd) spin_unlock_irqrestore(&dev->execute_task_lock, flags); } +/* + * This function is called by the target core after the target core has + * finished processing a SCSI command or SCSI TMF. Both the regular command + * processing code and the code for aborting commands can call this + * function. CMD_T_STOP is set if and only if another thread is waiting + * inside transport_wait_for_tasks() for t_transport_stop_comp. + */ static int transport_cmd_check_stop_to_fabric(struct se_cmd *cmd) { unsigned long flags; @@ -2624,6 +2631,27 @@ static void target_wait_free_cmd(struct se_cmd *cmd, bool *aborted, bool *tas) spin_unlock_irqrestore(&cmd->t_state_lock, flags); } +/* + * This function is called by frontend drivers after processing of a command + * has finished. + * + * The protocol for ensuring that either the regular flow or the TMF + * code drops one reference is as follows: + * - Calling .queue_data_in(), .queue_status() or queue_tm_rsp() will cause + * the frontend driver to drop one reference, synchronously or asynchronously. + * - During regular command processing the target core sets CMD_T_COMPLETE + * before invoking one of the .queue_*() functions. + * - The code that aborts commands skips commands and TMFs for which + * CMD_T_COMPLETE has been set. + * - CMD_T_ABORTED is set atomically after the CMD_T_COMPLETE check for + * commands that will be aborted. + * - If the CMD_T_ABORTED flag is set but CMD_T_TAS has not been set + * transport_generic_free_cmd() skips its call to target_put_sess_cmd(). + * - For aborted commands for which CMD_T_TAS has been set .queue_status() will + * be called and will drop a reference. + * - For aborted commands for which CMD_T_TAS has not been set .aborted_task() + * will be called. transport_cmd_finish_abort() will drop the final reference. + */ int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks) { int ret = 0; @@ -2652,12 +2680,6 @@ int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks) if (!aborted || tas) ret = target_put_sess_cmd(cmd); } - /* - * If the task has been internally aborted due to TMR ABORT_TASK - * or LUN_RESET, target_core_tmr.c is responsible for performing - * the remaining calls to target_put_sess_cmd(), and not the - * callers of this function. - */ if (aborted) { pr_debug("Detected CMD_T_ABORTED for ITT: %llu\n", cmd->tag); wait_for_completion(&cmd->cmd_wait_comp); |