On 2020/10/9 23:21, Jamie Iles wrote:
If ACPI is disabled then loading the acpi_dbg module will result in the
following splat when lock debugging is enabled.
DEBUG_LOCKS_WARN_ON(lock->magic != lock)
WARNING: CPU: 0 PID: 1 at kernel/locking/mutex.c:938 __mutex_lock+0xa10/0x1290
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc8+ #103
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x0/0x4d8
show_stack+0x34/0x48
dump_stack+0x174/0x1f8
panic+0x360/0x7a0
__warn+0x244/0x2ec
report_bug+0x240/0x398
bug_handler+0x50/0xc0
call_break_hook+0x160/0x1d8
brk_handler+0x30/0xc0
do_debug_exception+0x184/0x340
el1_dbg+0x48/0xb0
el1_sync_handler+0x170/0x1c8
el1_sync+0x80/0x100
__mutex_lock+0xa10/0x1290
mutex_lock_nested+0x6c/0xc0
acpi_register_debugger+0x40/0x88
acpi_aml_init+0xc4/0x114
do_one_initcall+0x24c/0xb10
kernel_init_freeable+0x690/0x728
kernel_init+0x20/0x1e8
ret_from_fork+0x10/0x18
That's because the mutex acpi_debugger.lock will not be initialized
as acpi_debugger_init() is not called if ACPI is disabled.
If you add above commit log then make it easier to be understood.
Fail module loading to avoid this and any subsequent problems that might
arise by trying to debug AML when ACPI is disabled.
It's better to add a fix tag:
Fixes: 8cfb0cdf07e2 ("ACPI / debugger: Add IO interface to access
debugger functionalities")
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Signed-off-by: Jamie Iles <jamie@xxxxxxxxxxxx>
---
drivers/acpi/acpi_dbg.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/acpi/acpi_dbg.c b/drivers/acpi/acpi_dbg.c
index 6041974c7627..fb7290338593 100644
--- a/drivers/acpi/acpi_dbg.c
+++ b/drivers/acpi/acpi_dbg.c
@@ -749,6 +749,9 @@ static int __init acpi_aml_init(void)
{
int ret;
+ if (acpi_disabled)
+ return -ENODEV;
+
/* Initialize AML IO interface */
mutex_init(&acpi_aml_io.lock);
init_waitqueue_head(&acpi_aml_io.wait);
With above comments addressed, feel free to add
Reviewed-by: Hanjun Guo <guohanjun@xxxxxxxxxx>
Thanks
Hanjun
