On Wed, 2016-05-18 at 14:35 -0500, Michael Cyr wrote: > On 5/18/16 12:53 AM, Nicholas A. Bellinger wrote: > > Hi Michael, > > > > On Fri, 2016-05-13 at 17:15 -0500, Michael Cyr wrote: > >> If a command with a Simple task attribute is failed due to a Unit > >> Attention, then a subsequent command with an Ordered task attribute will > >> hang forever. The reason for this is that the Unit Attention status is > >> checked for in target_setup_cmd_from_cdb, before the call to > >> target_execute_cmd, which calls target_handle_task_attr, which in turn > >> increments dev->simple_cmds. However, transport_generic_request_failure > >> still calls transport_complete_task_attr, which will decrement > >> dev->simple_cmds. In this case, simple_cmds is now -1. So when a > >> command with the Ordered task attribute is sent, target_handle_task_attr > >> sees that dev->simple_cmds is not 0, so it decides it can't execute the > >> command until all the (nonexistent) Simple commands have completed. > >> > > Thanks for reporting this bug. Comments below. <SNIP> > > So AFAICT for delayed commands, the above patch ends up skipping these > > three checks subsequently when doing __target_execute_cmd() directly > > from target_restart_delayed_cmds(), no..? > > > > After pondering this some more, what about moving these checks into > > __target_execute_cmd() to handle both target_core_transport.c cases > > instead..? >> > You're right, __target_execute_cmd is clearly the right place for the > checks. > > > We'll also need a parameter for internal COMPARE_AND_WRITE usage > > within compare_and_write_callback(), to bypass checks upon secondary > > ->execute_cmd() WRITE payload submission after READ + COMPARE has > > completed successfully. >> > I'm still learning about the target code, and I was unaware of > COMPARE_AND_WRITE. Thanks for pointing this out to me. You're right > here too, we need to make sure we only make the tests when the Compare > and Write is first executed (to do the read), and not later when the > write is done. > > > > WDYT..? >> > You've covered all the places that call __target_execute_cmd, so I think > it's good. Thanks for the feedback. Given the nature of the change, it needs some more Reviewed-by + Tested-By (across different drivers) ahead of pushing this patch into mainline. So for the moment it's in target-pending/queue as a post v4.7-rc1 item here: https://git.kernel.org/cgit/linux/kernel/git/nab/target-pending.git/commit/?h=queue&id=0c141c33b667b6538e38b87db87232523bcd4f5b -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
