On Mon, May 02, 2016 at 03:14:34PM -0700, Bart Van Assche wrote:
> I just noticed that ib_comp_wq is created as follows:
>
> ib_comp_wq = alloc_workqueue("ib-comp-wq",
> WQ_UNBOUND | WQ_HIGHPRI | WQ_MEM_RECLAIM,
> WQ_UNBOUND_MAX_ACTIVE);
>
> I think this breaks the locking guarantees for completion handlers. A quote
> from Documentation/infiniband/core_locking.txt: "The driver must guarantee
> that only one CQ event handler for a given CQ is running at a time." The
> ib_srpt driver assumes that completion handler invocations are serialized
> such that no locking is needed to access wait_list from inside a completion
> handler.
This should still be the case - the max_active argument to alloc_workqueue
just specified the amount of work_structs that may be exectured on the
workqueue concurrently, but each individual work_struct can only be
excuted once at a time. See the following paragraph in
Documentation/workqueue.txt:
"Note that the flag WQ_NON_REENTRANT no longer exists as all workqueues
are now non-reentrant - any work item is guaranteed to be executed by
at most one worker system-wide at any given time."
--
To unsubscribe from this list: send the line "unsubscribe target-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
