linux-kernel - [PATCH 4.10 34/75] pci/hotplug/pnv-php: Remove WARN_ON() in pnv_php_put

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Date:   Mon, 13 Mar 2017 16:43:43 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Gavin Shan <gwshan@...ux.vnet.ibm.com>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.10 34/75] pci/hotplug/pnv-php: Remove WARN_ON() in pnv_php_put_slot()

4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gavin Shan <gwshan@...ux.vnet.ibm.com>

commit 36c7c9da40c408a71e5e6bfe12e57dcf549a296d upstream.

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

Fixes: 66725152fb9f ("PCI/hotplug: PowerPC PowerNV PCI hotplug driver")
Signed-off-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@....ibm.com>
Tested-by: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -82,7 +82,7 @@ static void pnv_php_free_slot(struct kre
 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);