eh_abort_handler and calling scsi_done

From this and from looking at the code, i would conclude:

I am investigating what is required from a LLD when SCSI commands time out and the SCSI EH calls the eh_abort_handler. The documentation in scsi_eh.txt states:

<<scsi_eh_abort_cmds>>

This action is taken for each timed out command. hostt->eh_abort_handler() is invoked for each scmd. The handler returns SUCCESS if it has succeeded to make LLDD and all related hardware forget about the scmd.

From this and from looking at the code, i would conclude:

1) If the LLD returns FAILED from the eh_abort_handler, then the command is still allowed to be active in the LLD and the LLD can call scsi_done any time later (probably latest when the eh_host_reset_handler flushes everything that is still pending).

2) While the abort is pending, but before returning SUCCESS from eh_abort_handler, the LLD can still call scsi_done for the SCSI command to be aborted (the SCSI command might be returned with a status "aborted" if the abort succeeds, or "good" if it was completed just before the abort reached the storage system).

Is this correct? Are there any more limitations a SCSI LLD has to be aware of?

--
Christof Schmitt
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Your assessment sounds correct to me. The other caveat to note is that if for some reason in your eh_abort_handler you don't think the command is still outstanding, you should return SUCCESS for this as well.

Your assessment sounds correct to me. The other caveat to note is that if for some reason in your eh_abort_handler you don't think the command is still outstanding, you should return SUCCESS for this as well.

-Brian

Quoted 24 lines · Christof Schmitt

I am investigating what is required from a LLD when SCSI commands time out and the SCSI EH calls the eh_abort_handler. The documentation in scsi_eh.txt states:

<<scsi_eh_abort_cmds>>

This action is taken for each timed out command. hostt->eh_abort_handler() is invoked for each scmd. The handler returns SUCCESS if it has succeeded to make LLDD and all related hardware forget about the scmd.

From this and from looking at the code, i would conclude:

1) If the LLD returns FAILED from the eh_abort_handler, then the command is still allowed to be active in the LLD and the LLD can call scsi_done any time later (probably latest when the eh_host_reset_handler flushes everything that is still pending).

2) While the abort is pending, but before returning SUCCESS from eh_abort_handler, the LLD can still call scsi_done for the SCSI command to be aborted (the SCSI command might be returned with a status "aborted" if the abort succeeds, or "good" if it was completed just before the abort reached the storage system).

Quoted 4 lines · Brian King

Your assessment sounds correct to me. The other caveat to note is that if for some reason in your eh_abort_handler you don't think the command is still outstanding, you should return SUCCESS for this as well.

Quoted 27 lines

-Brian

Quoted 24 lines · Christof Schmitt

I am investigating what is required from a LLD when SCSI commands time out and the SCSI EH calls the eh_abort_handler. The documentation in scsi_eh.txt states:

<<scsi_eh_abort_cmds>>

This action is taken for each timed out command. hostt->eh_abort_handler() is invoked for each scmd. The handler returns SUCCESS if it has succeeded to make LLDD and all related hardware forget about the scmd.

From this and from looking at the code, i would conclude:

1) If the LLD returns FAILED from the eh_abort_handler, then the command is still allowed to be active in the LLD and the LLD can call scsi_done any time later (probably latest when the eh_host_reset_handler flushes everything that is still pending).

2) While the abort is pending, but before returning SUCCESS from eh_abort_handler, the LLD can still call scsi_done for the SCSI command to be aborted (the SCSI command might be returned with a status "aborted" if the abort succeeds, or "good" if it was completed just before the abort reached the storage system).

In cases 1 and 2 above calling scsi_done can be done but will cause the request to be stopped in blk_complete_request (scsi_done->blk_complete_request) as the timed out handler has already taken ownership of the command.

Quoted 32 lines · Mike Anderson

Quoted 4 lines · Brian King

Your assessment sounds correct to me. The other caveat to note is that if for some reason in your eh_abort_handler you don't think the command is still outstanding, you should return SUCCESS for this as well.

Quoted 27 lines

-Brian

Quoted 24 lines · Christof Schmitt

I am investigating what is required from a LLD when SCSI commands time out and the SCSI EH calls the eh_abort_handler. The documentation in scsi_eh.txt states:

<<scsi_eh_abort_cmds>>

This action is taken for each timed out command. hostt->eh_abort_handler() is invoked for each scmd. The handler returns SUCCESS if it has succeeded to make LLDD and all related hardware forget about the scmd.

From this and from looking at the code, i would conclude:

1) If the LLD returns FAILED from the eh_abort_handler, then the command is still allowed to be active in the LLD and the LLD can call scsi_done any time later (probably latest when the eh_host_reset_handler flushes everything that is still pending).

2) While the abort is pending, but before returning SUCCESS from eh_abort_handler, the LLD can still call scsi_done for the SCSI command to be aborted (the SCSI command might be returned with a status "aborted" if the abort succeeds, or "good" if it was completed just before the abort reached the storage system).

Quoted 4 lines

In cases 1 and 2 above calling scsi_done can be done but will cause the request to be stopped in blk_complete_request (scsi_done->blk_complete_request) as the timed out handler has already taken ownership of the command.

I am not too familiar with the blk completion handling. Would calling scsi_done for the cases above cause any problems? If there are reasons not to call scsi_done here, then this could be mentioned in the scsi documentation file.