netdev - Re: [PATCH v2] Bluetooth: Allow suspend even when preparation has failed

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Date:   Fri, 5 Jun 2020 13:44:52 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
Cc:     marcel@...tmann.org, linux-bluetooth@...r.kernel.org,
        len.brown@...el.com, chromeos-bluetooth-upstreaming@...omium.org,
        linux-pm@...r.kernel.org, rafael@...nel.org,
        todd.e.brandt@...ux.intel.com, rui.zhang@...el.com,
        "David S. Miller" <davem@...emloft.net>,
        Johan Hedberg <johan.hedberg@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Bluetooth: Allow suspend even when preparation has
 failed

On Thu,  4 Jun 2020 21:28:50 -0700 Abhishek Pandit-Subedi wrote:
> It is preferable to allow suspend even when Bluetooth has problems
> preparing for sleep. When Bluetooth fails to finish preparing for
> suspend, log the error and allow the suspend notifier to continue
> instead.
> 
> To also make it clearer why suspend failed, change bt_dev_dbg to
> bt_dev_err when handling the suspend timeout.
> 
> Fixes: dd522a7429b07e ("Bluetooth: Handle LE devices during suspend")
> Reported-by: Len Brown <len.brown@...el.com>
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> ---
> To verify this is properly working, I added an additional change to
> hci_suspend_wait_event to always return -16. This validates that suspend
> continues even when an error has occurred during the suspend
> preparation.
> 
> Example on Chromebook:
> [   55.834524] PM: Syncing filesystems ... done.
> [   55.841930] PM: Preparing system for sleep (s2idle)
> [   55.940492] Bluetooth: hci_core.c:hci_suspend_notifier() hci0: Suspend notifier action (3) failed: -16
> [   55.940497] Freezing user space processes ... (elapsed 0.001 seconds) done.
> [   55.941692] OOM killer disabled.
> [   55.941693] Freezing remaining freezable tasks ... (elapsed 0.000 seconds) done.
> [   55.942632] PM: Suspending system (s2idle)
> 
> I ran this through a suspend_stress_test in the following scenarios:
> * Peer classic device connected: 50+ suspends
> * No devices connected: 100 suspends
> * With the above test case returning -EBUSY: 50 suspends
> 
> I also ran this through our automated testing for suspend and wake on
> BT from suspend continues to work.
> 
> 
> Changes in v2:
> - Added fixes and reported-by tags

Building W=1 C=1 gcc-10:

In file included from ../net/bluetooth/hci_core.c:38:
../net/bluetooth/hci_core.c: In function â€˜hci_suspend_notifierâ€™:
../include/net/bluetooth/bluetooth.h:182:9: warning: format â€˜%xâ€™ expects argument of type â€˜unsigned intâ€™, but argument 3 has type â€˜long unsigned intâ€™ [-Wformat=]
  182 |  BT_ERR("%s: " fmt, (hdev)->name, ##__VA_ARGS__)
      |         ^~~~~~
../include/net/bluetooth/bluetooth.h:169:33: note: in definition of macro â€˜BT_ERRâ€™
  169 | #define BT_ERR(fmt, ...) bt_err(fmt "\n", ##__VA_ARGS__)
      |                                 ^~~
../net/bluetooth/hci_core.c:3368:3: note: in expansion of macro â€˜bt_dev_errâ€™
 3368 |   bt_dev_err(hdev, "Suspend notifier action (%x) failed: %d",
      |   ^~~~~~~~~~