[linux-azure:xenial][PATCH] PCI: hv: Do not sleep in compose_msi_msg()

[Marcelo Henrique Cerri]

From: Stephen Hemminger <stephen at networkplumber.org>

BugLink: http://bugs.launchpad.net/bugs/1747543

The setup of MSI with Hyper-V host was sleeping with locks held.  This
error is reported when doing SR-IOV hotplug with kernel built with lockdep:

    BUG: sleeping function called from invalid context at kernel/sched/completion.c:93
    in_atomic(): 1, irqs_disabled(): 1, pid: 1405, name: ip
    3 locks held by ip/1405:
   #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff976b10bb>] rtnetlink_rcv+0x1b/0x40
   #1:  (&desc->request_mutex){+.+...}, at: [<ffffffff970ddd33>] __setup_irq+0xb3/0x720
   #2:  (&irq_desc_lock_class){-.-...}, at: [<ffffffff970ddd65>] __setup_irq+0xe5/0x720
   irq event stamp: 3476
   hardirqs last  enabled at (3475): [<ffffffff971b3005>] get_page_from_freelist+0x225/0xc90
   hardirqs last disabled at (3476): [<ffffffff978024e7>] _raw_spin_lock_irqsave+0x27/0x90
   softirqs last  enabled at (2446): [<ffffffffc05ef0b0>] ixgbevf_configure+0x380/0x7c0 [ixgbevf]
   softirqs last disabled at (2444): [<ffffffffc05ef08d>] ixgbevf_configure+0x35d/0x7c0 [ixgbevf]

The workaround is to poll for host response instead of blocking on
completion.

Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
(cherry picked from commit 80bfeeb9dd6b54ac108c884c792f0fc7d4912bee)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>
---
 drivers/pci/host/pci-hyperv.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 9ade00572399..8b5f66d3c4f2 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -50,6 +50,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/delay.h>
 #include <linux/semaphore.h>
 #include <linux/irqdomain.h>
 #include <asm/irqdomain.h>
@@ -1115,7 +1116,12 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		goto free_int_desc;
 	}
 
-	wait_for_completion(&comp.comp_pkt.host_event);
+	/*
+	 * Since this function is called with IRQ locks held, can't
+	 * do normal wait for completion; instead poll.
+	 */
+	while (!try_wait_for_completion(&comp.comp_pkt.host_event))
+		udelay(100);
 
 	if (comp.comp_pkt.completion_status < 0) {
 		dev_err(&hbus->hdev->device,
-- 
2.7.4