[PATCH 1/1] powerpc/pseries: Use the system workqueue as fallback to hotplug workqueue

[Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>]

The hotplug engine uses its own workqueue to handle IRQ requests, the
problem is that such workqueue is initialized not so early in the boot
process.

Thus, when the kernel is ready to handle IRQ requests, after the system
workqueue is initialized, we have a timeframe where any hotplug issued
by the client will result in a kernel panic. That timeframe goes until
the hotplug workqueue is initialized.

It would be good to have the hotplug workqueue initialized as soon as
the system workqueue but I don't think it is possible. So, this patch
uses the system workqueue as a fallback the handle such IRQs.

Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/dlpar.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
index 6e35780c5962..0474aa14b5f6 100644
--- a/arch/powerpc/platforms/pseries/dlpar.c
+++ b/arch/powerpc/platforms/pseries/dlpar.c
@@ -399,7 +399,15 @@ void queue_hotplug_event(struct pseries_hp_errorlog *hp_errlog,
 		work->errlog = hp_errlog_copy;
 		work->hp_completion = hotplug_done;
 		work->rc = rc;
-		queue_work(pseries_hp_wq, (struct work_struct *)work);
+
+		/* The hotplug workqueue may happen to be NULL at the moment
+		 * this code is executed, during the boot phase. So, in this
+		 * scenario, we can fallback to the system workqueue.
+		 */
+		if (unlikely(pseries_hp_wq == NULL))
+			schedule_work((struct work_struct *)work);
+		else
+			queue_work(pseries_hp_wq, (struct work_struct *)work);
 	} else {
 		*rc = -ENOMEM;
 		kfree(hp_errlog_copy);
-- 
2.14.1