ACK/cmnt: [SRU Xenial][v4][PATCH] UBUNTU: SAUCE: Redpine: improve cancel_hw_scan handling to fix kernel panic

[Anthony Wong]

On Fri, Jul 20, 2018 at 10:23:17AM +0800, Shrirang Bagul wrote:
> On Mon, 2018-07-16 at 19:29 +0530, Siva Rebbagondla wrote:
> > From: Siva Rebbagondla <siva.rebbagondla at redpinesignals.com>
> > 
> > BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1773410
> > BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1777850
> 
> Siva, please use the correct format for buglinks, these bug links should be:
> BugLink: https://bugs.launchpad.net/bugs/1773410
> BugLink: https://bugs.launchpad.net/bugs/1777850
> 
> > Kernel panic is observed when network manager is stopped or Interface is
> > is DOWN, 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().
> > 
> > ...skipping...
> > [ 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>

Confirmed offline with Shrirang that this patch has been verified by
our QA and does not cause any regression. BugLink needs fixing though.

Acked-by: Anthony Wong <anthony.wong at canonical.com>