From: Wei Fang <fangwei1@xxxxxxxxxx>
This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit 72d8c36ec364c82bf1bf0c64dfa1041cfaf139f7 ]
sas_ata_strategy_handler() adds the works of the ata error handler to
system_unbound_wq. This workqueue asynchronously runs work items, so the
ata error handler will be performed concurrently on different CPUs. In
this case, ->host_failed will be decreased simultaneously in
scsi_eh_finish_cmd() on different CPUs, and become abnormal.
It will lead to permanently inequality between ->host_failed and
->host_busy, and scsi error handler thread won't start running. IO
errors after that won't be handled.
Since all scmds must have been handled in the strategy handler, just
remove the decrement in scsi_eh_finish_cmd() and zero ->host_busy after
the strategy handler to fix this race.
Fixes: 50824d6c5657 ("[SCSI] libsas: async ata-eh")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wei Fang <fangwei1@xxxxxxxxxx>
Reviewed-by: James Bottomley <jejb@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
Documentation/scsi/scsi_eh.txt | 8 ++++++--
drivers/ata/libata-eh.c | 2 +-
drivers/scsi/scsi_error.c | 4 +++-
3 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/Documentation/scsi/scsi_eh.txt b/Documentation/scsi/scsi_eh.txt
index 8638f61..37eca00 100644
--- a/Documentation/scsi/scsi_eh.txt
+++ b/Documentation/scsi/scsi_eh.txt
@@ -263,19 +263,23 @@ 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
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index cb0508a..5ab6fa9 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -606,7 +606,7 @@ void ata_scsi_error(struct Scsi_Host *host)
ata_scsi_port_error_handler(host, ap);
/* finish or retry handled scmd's and clean up */
- WARN_ON(host->host_failed || !list_empty(&eh_work_q));
+ WARN_ON(!list_empty(&eh_work_q));
DPRINTK("EXIT\n");
}
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index c6b93d2..841fdf7 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1122,7 +1122,6 @@ static int scsi_eh_action(struct scsi_cmnd *scmd, int rtn)
*/
void scsi_eh_finish_cmd(struct scsi_cmnd *scmd, struct list_head *done_q)
{
- scmd->device->host->host_failed--;
scmd->eh_eflags = 0;
list_move_tail(&scmd->eh_entry, done_q);
}
@@ -2216,6 +2215,9 @@ int scsi_error_handler(void *data)
else
scsi_unjam_host(shost);
+ /* All scmds have been handled */
+ shost->host_failed = 0;
+
/*
* Note - if the above fails completely, the action is to take
* individual devices offline and flush the queue of any
--
2.5.0
--
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