linux-kernel - Re: [PATCH v4 2/2] firmware_loader: Abort all upcoming firmware load request once reboot triggered

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Date:   Thu, 26 Oct 2023 14:17:25 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>
Cc:     Russ Weight <russ.weight@...ux.dev>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] firmware_loader: Abort all upcoming firmware load
 request once reboot triggered

On Thu, Oct 26, 2023 at 07:57:39PM +0530, Mukesh Ojha wrote:
> There could be following scenario where there is a ongoing reboot
> is going from processA which tries to call all the reboot notifier
> callback and one of them is firmware reboot call which tries to
> abort all the ongoing firmware userspace request under fw_lock but
> there could be another processB which tries to do request firmware,
> which came just after abort done from ProcessA and ask for userspace
> to load the firmware and this can stop the ongoing reboot ProcessA
> to stall for next 60s(default timeout) which may not be expected
> behaviour everyone like to see, instead we should abort any firmware
> load request which came once firmware knows about the reboot through
> notification.
> 
>       ProcessA                             ProcessB
> 
> kernel_restart_prepare
>   blocking_notifier_call_chain
>    fw_shutdown_notify
>      kill_pending_fw_fallback_reqs
>       __fw_load_abort
>        fw_state_aborted                request_firmware
>          __fw_state_set                 firmware_fallback_sysfs
> ...                                       fw_load_from_user_helper
> ..                                         ...
> .                                          ..
>                                             usermodehelper_read_trylock
>                                              fw_load_sysfs_fallback
>                                               fw_sysfs_wait_timeout
> usermodehelper_disable
>  __usermodehelper_disable
>   down_write()
> 
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---

Acked-by: Luis Chamberlain <mcgrof@...nel.org>

  Luis