On Sun, May 29, 2016 at 08:41:13AM -0700, James Bottomley wrote:
> Actually, it doesn't look fine at all. The same mechanism that's
> supposed to protect the host_failed decrement is also supposed to
> protect the list_move_tail(). If there's a problem with the former
> then we're also in danger of corrupting the list.
No, that's not the case. eh_entry is used for two things:
a) shost->eh_cmd_q, which is used to queue up command for the EH
thread, and is locked using the host lock.
b) various on-stack lists in the EH thread
scsi_eh_finish_cmd is only called for case b) as all EH thread
implementations move the commands from eh_cmd_q to a local list
as the very first thing.
host_fail on the other hand is incremented under the host_lock
in scsi_eh_scmd_add, but decremented without any lock from the
EH thread.
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