On Thu, 23 Sept 2021 at 04:51, Zhang Jianhua <chris.zjh@xxxxxxxxxx> wrote:
>
> While reboot the system by sysrq, the following bug will be occur.
>
> BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:90
> in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 10052, name: rc.shutdown
> CPU: 3 PID: 10052 Comm: rc.shutdown Tainted: G W O 5.10.0 #1
> Call trace:
> dump_backtrace+0x0/0x1c8
> show_stack+0x18/0x28
> dump_stack+0xd0/0x110
> ___might_sleep+0x14c/0x160
> __might_sleep+0x74/0x88
> down_interruptible+0x40/0x118
> virt_efi_reset_system+0x3c/0xd0
> efi_reboot+0xd4/0x11c
> machine_restart+0x60/0x9c
> emergency_restart+0x1c/0x2c
> sysrq_handle_reboot+0x1c/0x2c
> __handle_sysrq+0xd0/0x194
> write_sysrq_trigger+0xbc/0xe4
> proc_reg_write+0xd4/0xf0
> vfs_write+0xa8/0x148
> ksys_write+0x6c/0xd8
> __arm64_sys_write+0x18/0x28
> el0_svc_common.constprop.3+0xe4/0x16c
> do_el0_svc+0x1c/0x2c
> el0_svc+0x20/0x30
> el0_sync_handler+0x80/0x17c
> el0_sync+0x158/0x180
>
> The reason for this problem is that irq has been disabled in
> machine_restart() and then it calls down_interruptible() in
> virt_efi_reset_system(), which would occur sleep in irq context,
> it is dangerous! Commit 99409b935c9a("locking/semaphore: Add
> might_sleep() to down_*() family") add might_sleep() in
> down_interruptible(), so the bug info is here. down_trylock()
> can solve this problem, cause there is no might_sleep.
>
> --------
>
> Signed-off-by: Zhang Jianhua <chris.zjh@xxxxxxxxxx>
Thanks. I will queue this up.
> ---
> drivers/firmware/efi/runtime-wrappers.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index 1410beaef5c3..f3e54f6616f0 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -414,7 +414,7 @@ static void virt_efi_reset_system(int reset_type,
> unsigned long data_size,
> efi_char16_t *data)
> {
> - if (down_interruptible(&efi_runtime_lock)) {
> + if (down_trylock(&efi_runtime_lock)) {
> pr_warn("failed to invoke the reset_system() runtime service:\n"
> "could not get exclusive access to the firmware\n");
> return;
> --
> 2.31.0
>
