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

[Shrirang Bagul]

On Wed, 2018-06-20 at 19:13 +0530, Siva Rebbagondla wrote:
> 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>
Acked-By: Shrirang Bagul <shrirang.bagul at canonical.com>
> ---
> v2: Added enhancement in case of AP mode [Shrirang]
Why do you need my name in the changelog of the patch?
> ---
>  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
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