WARNING: suspicious RCU usage

[Fabio Estevam]

Hi Russell,

On Tue, Dec 12, 2017 at 3:34 PM, Russell King - ARM Linux
<linux at armlinux.org.uk> wrote:

> It's fundamentally unsafe.
>
> You need to test with CONFIG_BL_SWITCHER enabled - there's spinlocks
> in smp_call_function_single() path that are conditional on that symbol.
> If CONFIG_BL_SWITCHER is disabled, then the spinlocks are not present.

Ok, just tested with CONFIG_BL_SWITCHER=y on a imx6q-cubox-i:

# echo enabled > /sys/class/tty/ttymxc0/power/wakeup
# echo mem > /sys/power/state
[   10.503462] PM: suspend entry (deep)
[   10.507479] PM: Syncing filesystems ... done.
[   10.555024] Freezing user space processes ... (elapsed 0.002 seconds) done.
[   10.564511] OOM killer disabled.
[   10.567760] Freezing remaining freezable tasks ... (elapsed 0.002 seconds) d.
[   10.577420] Suspending console(s) (use no_console_suspend to debug)
[   10.657748] PM: suspend devices took 0.080 seconds
[   10.669329] Disabling non-boot CPUs ...
[   10.717049] IRQ17 no longer affine to CPU1
[   10.837141] Enabling non-boot CPUs ...
[   10.839386] CPU1 is up
[   10.840342] CPU2 is up
[   10.841300] CPU3 is up
[   11.113735] mmc0: queuing unknown CIS tuple 0x80 (2 bytes)
[   11.115676] mmc0: queuing unknown CIS tuple 0x80 (3 bytes)
[   11.117595] mmc0: queuing unknown CIS tuple 0x80 (3 bytes)
[   11.121014] mmc0: queuing unknown CIS tuple 0x80 (7 bytes)
[   11.124454] mmc0: queuing unknown CIS tuple 0x80 (7 bytes)
[   11.177299] ata1: SATA link down (SStatus 0 SControl 300)
[   11.181930] PM: resume devices took 0.330 seconds
[   11.243729] OOM killer enabled.
[   11.246886] Restarting tasks ... done.
[   11.253012] PM: suspend exit