scsi: fix race between simultaneous decrements of ->host_failed

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / scsi / scsi_eh.txt

diff --git a/Documentation/scsi/scsi_eh.txt b/Documentation/scsi/scsi_eh.txt
index 6ff16b620d84cf63d3e6e669a0cb7dab7d350c54..c08b62d63afa1bc2c81f9607a8921e774c856ad5 100644 (file)
--- a/Documentation/scsi/scsi_eh.txt
+++ b/Documentation/scsi/scsi_eh.txt
@@ -255,19 +255,23 @@ scmd->allowed.
 
  3. scmd recovered
     ACTION: scsi_eh_finish_cmd() is invoked to EH-finish scmd
-       - shost->host_failed--
        - clear scmd->eh_eflags
        - scsi_setup_cmd_retry()
        - move from local eh_work_q to local eh_done_q
     LOCKING: none
+    CONCURRENCY: at most one thread per separate eh_work_q to
+                keep queue manipulation lockless
 
  4. EH completes
     ACTION: scsi_eh_flush_done_q() retries scmds or notifies upper
-           layer of failure.
+           layer of failure. May be called concurrently but must have
+           a no more than one thread per separate eh_work_q to
+           manipulate the queue locklessly
        - scmd is removed from eh_done_q and scmd->eh_entry is cleared
        - if retry is necessary, scmd is requeued using
           scsi_queue_insert()
        - otherwise, scsi_finish_command() is invoked for scmd
+       - zero shost->host_failed
     LOCKING: queue or finish function performs appropriate locking