Hi Pankaj, ---- On Fri, 02 Jan 2026 20:29:59 +0800 Pankaj Gupta <[email protected]> wrote --- > +CC MST > > virtio_pmem_host_ack() reclaims virtqueue descriptors with > > virtqueue_get_buf(). The -ENOSPC waiter wakeup is tied to completing the > > returned token. > > > > If token completion is skipped for any reason, reclaimed descriptors may > > not wake a waiter and the submitter may sleep forever waiting for a free > > slot. > > > > Always wake one -ENOSPC waiter for each virtqueue completion before > > touching the returned token. > > > > Use READ_ONCE()/WRITE_ONCE() for the wait_event() flags (done and > > wq_buf_avail). They are observed by waiters without pmem_lock, so make > > the accesses explicit single loads/stores and avoid compiler > > reordering/caching across the wait/wake paths. > > > > Signed-off-by: Li Chen <[email protected]> > > --- > > drivers/nvdimm/nd_virtio.c | 35 +++++++++++++++++++++-------------- > > 1 file changed, 21 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > > index c3f07be4aa22..6f9890361d0b 100644 > > --- a/drivers/nvdimm/nd_virtio.c > > +++ b/drivers/nvdimm/nd_virtio.c > > @@ -9,26 +9,33 @@ > > #include "virtio_pmem.h" > > #include "nd.h" > > > > +static void virtio_pmem_wake_one_waiter(struct virtio_pmem *vpmem) > > +{ > > + struct virtio_pmem_request *req_buf; > > + > > + if (list_empty(&vpmem->req_list)) > > + return; > > + > > + req_buf = list_first_entry(&vpmem->req_list, > > + struct virtio_pmem_request, list); > > [...] > > + list_del_init(&req_buf->list); > > + WRITE_ONCE(req_buf->wq_buf_avail, true); > > + wake_up(&req_buf->wq_buf); > > Seems with the above change (3 line fix), you are allowing to wakeup a waiter > before accessing the token. Maybe simplify the patch by just > keeping this change in the single patch & other changes > (READ_ONCE/WRITE_ONCE) > onto separate patch with corresponding commit log.
Sorry for the late reply, I just realized I somehow missed this email :-p Thanks for the suggestion. I'll do it in v3. Regards, Li
