Re: [PATCH v2 1/2] scsi: fix race between simultaneous decrements of ->host_failed

On Tue, 2016-05-31 at 16:38 +0800, Wei Fang wrote:

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 inequal between ->host_failed and
 ->host_busy, and scsi error handler thread won't become running.
IO errors after that won't be handled forever.

Use atomic type for ->host_failed to fix this race.

As I said previously, you don't need atomics to do this, could you just
remove the decrement in scsi_eh_finish_command() and zero the counter
after the strategy handler completes.

Thanks,

James