IB/hfi1: Prevent kernel QP post send hard lockups

The driver progress routines can call cond_resched() when
a timeslice is exhausted and irqs are enabled.

If the ULP had been holding a spin lock without disabling irqs and
the post send directly called the progress routine, the cond_resched()
could yield allowing another thread from the same ULP to deadlock
on that same lock.

Correct by replacing the current hfi1_do_send() calldown with a unique
one for post send and adding an argument to hfi1_do_send() to indicate
that the send engine is running in a thread.   If the routine is not
running in a thread, avoid calling cond_resched().

CC: <stable@vger.kernel.org> # 4.7.x-
Fixes: Commit 831464ce ("IB/hfi1: Don't call cond_resched in atomic mode when sending packets")
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/ruc.c

 /*
- * Copyright(c) 2015, 2016 Intel Corporation.
+ * Copyright(c) 2015 - 2017 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -784,23 +784,29 @@ void hfi1_make_ruc_header(struct rvt_qp *qp, struct ib_other_headers *ohdr,
 /* when sending, force a reschedule every one of these periods */
 #define SEND_RESCHED_TIMEOUT (5 * HZ)  /* 5s in jiffies */
 
+void hfi1_do_send_from_rvt(struct rvt_qp *qp)
+{
+	hfi1_do_send(qp, false);
+}
+
 void _hfi1_do_send(struct work_struct *work)
 {
 	struct iowait *wait = container_of(work, struct iowait, iowork);
 	struct rvt_qp *qp = iowait_to_qp(wait);
 
-	hfi1_do_send(qp);
+	hfi1_do_send(qp, true);
 }
 
 /**
  * hfi1_do_send - perform a send on a QP
  * @work: contains a pointer to the QP
+ * @in_thread: true if in a workqueue thread
  *
  * Process entries in the send work queue until credit or queue is
  * exhausted.  Only allow one CPU to send a packet per QP.
  * Otherwise, two threads could send packets out of order.
  */
-void hfi1_do_send(struct rvt_qp *qp)
+void hfi1_do_send(struct rvt_qp *qp, bool in_thread)
 {
 	struct hfi1_pkt_state ps;
 	struct hfi1_qp_priv *priv = qp->priv;
@@ -868,7 +874,9 @@ void hfi1_do_send(struct rvt_qp *qp)
 			qp->s_hdrwords = 0;
 			/* allow other tasks to run */
 			if (unlikely(time_after(jiffies, timeout))) {
-				if (workqueue_congested(cpu,
+				if (!in_thread ||
+				    workqueue_congested(
+						cpu,
 						ps.ppd->hfi1_wq)) {
 					spin_lock_irqsave(
 						&qp->s_lock,
@@ -882,11 +890,9 @@ void hfi1_do_send(struct rvt_qp *qp)
 						*ps.ppd->dd->send_schedule);
 					return;
 				}
-				if (!irqs_disabled()) {
 				cond_resched();
 				this_cpu_inc(
 					*ps.ppd->dd->send_schedule);
-				}
 				timeout = jiffies + (timeout_int) / 8;
 			}
 			spin_lock_irqsave(&qp->s_lock, ps.flags);

drivers/infiniband/hw/hfi1/verbs.c

 /*
- * Copyright(c) 2015, 2016 Intel Corporation.
+ * Copyright(c) 2015 - 2017 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -1820,7 +1820,7 @@ int hfi1_register_ib_device(struct hfi1_devdata *dd)
 	dd->verbs_dev.rdi.driver_f.qp_priv_free = qp_priv_free;
 	dd->verbs_dev.rdi.driver_f.free_all_qps = free_all_qps;
 	dd->verbs_dev.rdi.driver_f.notify_qp_reset = notify_qp_reset;
-	dd->verbs_dev.rdi.driver_f.do_send = hfi1_do_send;
+	dd->verbs_dev.rdi.driver_f.do_send = hfi1_do_send_from_rvt;
 	dd->verbs_dev.rdi.driver_f.schedule_send = hfi1_schedule_send;
 	dd->verbs_dev.rdi.driver_f.schedule_send_no_lock = _hfi1_schedule_send;
 	dd->verbs_dev.rdi.driver_f.get_pmtu_from_attr = get_pmtu_from_attr;

drivers/infiniband/hw/hfi1/verbs.h

 /*
- * Copyright(c) 2015, 2016 Intel Corporation.
+ * Copyright(c) 2015 - 2017 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -355,7 +355,9 @@ void hfi1_make_ruc_header(struct rvt_qp *qp, struct ib_other_headers *ohdr,
 
 void _hfi1_do_send(struct work_struct *work);
 
-void hfi1_do_send(struct rvt_qp *qp);
+void hfi1_do_send_from_rvt(struct rvt_qp *qp);
+
+void hfi1_do_send(struct rvt_qp *qp, bool in_thread);
 
 void hfi1_send_complete(struct rvt_qp *qp, struct rvt_swqe *wqe,
 			enum ib_wc_status status);