[PATCH] kernel/kexec: remove the lock operation of system_transition_mutex

[Pingfan Liu]

On Fri, Jan 22, 2021 at 3:42 PM Baoquan He <bhe at redhat.com> wrote:
>
> Function kernel_kexec() is called with lock system_transition_mutex held
> in reboot system call. While inside kernel_kexec(), it will acquire
> system_transition_mutex agin. This will lead to dead lock.
>
> The dead lock should be easily triggered, it hasn't caused any failure
> report just because the feature 'kexec jump' is almost not used by anyone
> as far as I know. An inquiry can be made about who is using 'kexec jump'
> and where it's used. Before that, let's simply remove the lock operation
> inside CONFIG_KEXEC_JUMP ifdeffery scope.
>
> Signed-off-by: Baoquan He <bhe at redhat.com>
> Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
> Reviewed-by: Pingfan Liu <kernelfans at gmail.com>
> ---
>  kernel/kexec_core.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 80905e5aa8ae..a0b6780740c8 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -1134,7 +1134,6 @@ int kernel_kexec(void)
>
>  #ifdef CONFIG_KEXEC_JUMP
>         if (kexec_image->preserve_context) {
> -               lock_system_sleep();
>                 pm_prepare_console();
>                 error = freeze_processes();
>                 if (error) {
> @@ -1197,7 +1196,6 @@ int kernel_kexec(void)
>                 thaw_processes();
>   Restore_console:
>                 pm_restore_console();
> -               unlock_system_sleep();
>         }
>  #endif
>
> --
> 2.17.2
>
Reviewed-by: Pingfan Liu <kernelfans at gmail.com>