On Thu, Jan 31, 2019 at 01:56:15PM -0700, Parav Pandit wrote: > > > > From: linux-rdma-owner@xxxxxxxxxxxxxxx <linux-rdma- > > owner@xxxxxxxxxxxxxxx> On Behalf Of Steve Wise > > Sent: Thursday, January 31, 2019 1:31 PM > > To: dledford@xxxxxxxxxx; Jason Gunthorpe <jgg@xxxxxxxxxxxx> > > Cc: linux-rdma@xxxxxxxxxxxxxxx > > Subject: [PATCH rdma-next] RDMA/addr: create addr_wq with > > WQ_MEM_RECLAIM flag > > > > While running NVMe/oF wire unplug tests, we hit this warning in > > kernel/workqueue.c:check_flush_dependency(): > > > > WARN_ONCE(worker && ((worker->current_pwq->wq->flags & > > (WQ_MEM_RECLAIM | __WQ_LEGACY)) == > > WQ_MEM_RECLAIM), > > "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing > > !WQ_MEM_RECLAIM %s:%pf", > > worker->current_pwq->wq->name, worker->current_func, > > target_wq->name, target_func); > > > > Which I think means we're flushing a workq that doesn't have > > WQ_MEM_RECLAIM set, from workqueue context that does have it set. > > > > Looking at rdma_addr_cancel() which is doing the flushing, it flushes the > > addr_wq which doesn't have MEM_RECLAIM set. Yet rdma_addr_cancel() is > > being called by the nvme host connection timeout/reconnect workqueue > > thread that does have WQ_MEM_RECLAIM set. > > > > So set WQ_MEM_RECLAIM on the addr_req workqueue. > > > > Please add below [1] fixes by tag. > I removed this flag based on commit [2] of Sagi and discussion[3]. > Which I think [2] and [3] are incorrect. > > Memory reclaim path could have been triggered by processes or kernel > and I think it is ok to allocate a memory in a work item trigger as > part of reclaim path or otherwise. Memory allocation in a wq has > nothing to do with memory reclaim. I wish if Tejun or Christoph > confirm this is right or correct our understanding. Considering the only thing WQ_MEM_RECLAIM does is to pre-allocate a execution progress to guarentee forward progress if the system is unable to succed in memory allocations.. It seems a bit goofy to say that it is OK to then block on memory allocations inside that precious execution context.. I also would like to understand what the rules should be for this flag before applying this patch?? > Based these past discussions, it appears to me that WQ_MEM_RECLAIM > limitation and its use is not clear. I've always thought it was designed to guarentee forward progress if memory cannot be allocated. Jason
