[PATCH v2][Yakkety SRU] pci/hotplug/pnv-php: Remove WARN_ON() in pnv_php_put_slot()

[Seth Forshee]

From: Gavin Shan <gwshan at linux.vnet.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1667599

The WARN_ON() causes unnecessary backtrace when putting the parent
slot, which is likely to be NULL.

 WARNING: CPU: 2 PID: 1071 at drivers/pci/hotplug/pnv_php.c:85 \
                              pnv_php_release+0xcc/0x150 [pnv_php]
    :
 Call Trace:
 [c0000003bc007c10] [d00000000ad613c4] pnv_php_release+0x144/0x150 [pnv_php]
 [c0000003bc007c40] [c0000000006641d8] pci_hp_deregister+0x238/0x330
 [c0000003bc007cd0] [d00000000ad61440] pnv_php_unregister_one+0x70/0xa0 [pnv_php]
 [c0000003bc007d10] [d00000000ad614c0] pnv_php_unregister+0x50/0x80 [pnv_php]
 [c0000003bc007d40] [d00000000ad61e84] pnv_php_exit+0x50/0xcb4 [pnv_php]
 [c0000003bc007d70] [c00000000019499c] SyS_delete_module+0x1fc/0x2a0
 [c0000003bc007e30] [c00000000000b184] system_call+0x38/0xe0

Cc: <stable at vger.kernel.org> # v4.8+
Fixes: 66725152fb9f ("PCI/hotplug: PowerPC PowerNV PCI hotplug driver")
Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>
Tested-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
(cherry picked from linux-next commit 36c7c9da40c408a71e5e6bfe12e57dcf549a296d)
Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
---

v2:
 - Note that the commit came from linux-next.

 drivers/pci/hotplug/pnv_php.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index e6245b03f0a1..4308690b2ff3 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -42,7 +42,7 @@ static void pnv_php_free_slot(struct kref *kref)
 static inline void pnv_php_put_slot(struct pnv_php_slot *php_slot)
 {
 
-	if (WARN_ON(!php_slot))
+	if (!php_slot)
 		return;
 
 	kref_put(&php_slot->kref, pnv_php_free_slot);
-- 
2.7.4