[Xenial SRU][PATCH v2] UBUNTU: SAUCE: Redpine: improve cancel_hw_scan handling to fix kernel panic

[Siva Rebbagondla]

From: Siva Rebbagondla <siva.rebbagondla at redpinesignals.com>

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1773410
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1777850

Kernel panic is observed when network manager is stopped while system
is entering into hibernation. The root cause of the issue is scan work
function keeps running even after cancel_hw_scan() call.
Issue is resolved by calling cancel_work_sync().

[ 1171.913244] BUG: unable to handle page request at 00000000001067e38
[ 1171.913248] IP: cfg80211_scan_done+0xb0/0xc0 [cfg80211]
[ 1171.913554] Hardware name: Dell Inc. Edge Gateway 3003/      , BIOS 01.00.06 01/22/2018
[ 1171.913668] Workqueue: phy1 ieee80211_scan_work [mac80211]
[ 1171.913773] RIP: 0010:cfg80211_scan_done+0xb0/0xc0 [cfg80211]
[ 1171.913780] RSP: 0018:ffffc1fe41b47dc8 EFLAGS: 00010286
[ 1171.913789] RAX: 0000000000000001 RBX: ffffffffc0e60120 RCX: 0000000100080006
[ 1171.913794] RDX: ffff9eeab7e3bc58 RSI: ffff9eeab0c69080 RDI: ffff9eeab7e3bc00
[ 1171.913799] RBP: ffff9eeab7e3bc00 R08: 00000000b7e3b201 R09: 0000000100080006
[ 1171.913805] R10: ffffc1fe41b47d20 R11: 0000000000000000 R12: ffff9eeab0c69080
[ 1171.913810] R13: 0000000000000022 R14: ffff9eeab0c68760 R15: ffff9eeab7af3c00
[ 1171.913817] FS:  0000000000000000(0000) GS:ffff9eeab0000000(0000) knlGS:0000000000000000
[ 1171.913823] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1171.913828] CR2: 00007f76c73ac190 CR3: 000000006e20a000 CR4: 00000000001006f0
[ 1171.913833] Call Trace:
[ 1171.913864]  ? rsi_mac80211_sta_remove+0x260/0x260 [rsi_91x]
[ 1171.913971]  __ieee80211_scan_completed+0xb1/0x390 [mac80211]
[ 1171.914078]  ieee80211_scan_work+0x7e/0x480 [mac80211]
[ 1171.914098]  process_one_work+0x142/0x3d0
[ 1171.914111]  worker_thread+0x229/0x440
[ 1171.914122]  kthread+0xf5/0x130
[ 1171.914132]  ? process_one_work+0x3d0/0x3d0
[ 1171.914140]  ? kthread_associate_blkcg+0x90/0x90
[ 1171.914152]  ret_from_fork+0x35/0x40

Signed-off-by: Siva Rebbagondla <siva.rebbagondla at redpinesignals.com>
---
v2: Added enhancement in case of AP mode [Shrirang]
---
 ubuntu/rsi/rsi_91x_mac80211.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ubuntu/rsi/rsi_91x_mac80211.c b/ubuntu/rsi/rsi_91x_mac80211.c
index 36c0cfd..a797826 100644
--- a/ubuntu/rsi/rsi_91x_mac80211.c
+++ b/ubuntu/rsi/rsi_91x_mac80211.c
@@ -428,6 +428,7 @@ void rsi_mac80211_hw_scan_cancel(struct ieee80211_hw *hw,
 		rsi_wait_event(&common->cancel_hw_scan_event,
 			       EVENT_WAIT_FOREVER);
 		rsi_reset_event(&common->cancel_hw_scan_event);
+		cancel_work_sync(&common->scan_work);
 		common->scan_request = NULL;
 	}
 	
@@ -631,6 +632,7 @@ static void rsi_mac80211_stop(struct ieee80211_hw *hw)
 	
 	common->iface_down = true;
 #ifdef CONFIG_HW_SCAN_OFFLOAD
+	cancel_work_sync(&common->scan_work);
 	if (common->scan_in_prog) 
 		common->scan_in_prog = false;
 #endif
-- 
2.5.5