On Thu, May 25, 2023, at 3:41 PM, Hans de Goede wrote:
> Hi Mark,
>
> On 5/25/23 21:31, Mark Pearson wrote:
>> Add mutex protection around cases where an operation needs multiple
>> WMI calls - e.g. setting password.
>>
>> Signed-off-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>
>> ---
>> Changes in V2: New commit added after review of other patches in series.
>>
>> drivers/platform/x86/think-lmi.c | 46 ++++++++++++++++++++++++--------
>> 1 file changed, 35 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
>> index 64cd453d6e7d..f3e1e4dacba2 100644
>> --- a/drivers/platform/x86/think-lmi.c
>> +++ b/drivers/platform/x86/think-lmi.c
>> @@ -14,6 +14,7 @@
>> #include <linux/acpi.h>
>> #include <linux/errno.h>
>> #include <linux/fs.h>
>> +#include <linux/mutex.h>
>> #include <linux/string.h>
>> #include <linux/types.h>
>> #include <linux/dmi.h>
>> @@ -195,6 +196,7 @@ static const char * const level_options[] = {
>> };
>> static struct think_lmi tlmi_priv;
>> static struct class *fw_attr_class;
>> +static DEFINE_MUTEX(tlmi_mutex);
>>
>> /* ------ Utility functions ------------*/
>> /* Strip out CR if one is present */
>> @@ -463,23 +465,32 @@ static ssize_t new_password_store(struct kobject *kobj,
>> sprintf(pwd_type, "%s", setting->pwd_type);
>> }
>>
>> + mutex_lock(&tlmi_mutex);
>> ret = tlmi_opcode_setting("WmiOpcodePasswordType", pwd_type);
>> - if (ret)
>> + if (ret) {
>> + mutex_unlock(&tlmi_mutex);
>> goto out;
>> -
>> + }
>> if (tlmi_priv.pwd_admin->valid) {
>> ret = tlmi_opcode_setting("WmiOpcodePasswordAdmin",
>> tlmi_priv.pwd_admin->password);
>> - if (ret)
>> + if (ret) {
>> + mutex_unlock(&tlmi_mutex);
>> goto out;
>> + }
>> }
>> ret = tlmi_opcode_setting("WmiOpcodePasswordCurrent01", setting->password);
>> - if (ret)
>> + if (ret) {
>> + mutex_unlock(&tlmi_mutex);
>> goto out;
>> + }
>> ret = tlmi_opcode_setting("WmiOpcodePasswordNew01", new_pwd);
>> - if (ret)
>> + if (ret) {
>> + mutex_unlock(&tlmi_mutex);
>> goto out;
>> + }
>> ret = tlmi_simple_call(LENOVO_OPCODE_IF_GUID, "WmiOpcodePasswordSetUpdate;");
>> + mutex_unlock(&tlmi_mutex);
>> } else {
>> /* Format: 'PasswordType,CurrentPw,NewPw,Encoding,KbdLang;' */
>> auth_str = kasprintf(GFP_KERNEL, "%s,%s,%s,%s,%s;",
>
>
> I haven't take a really close / good look yet. But at a first glance
> I think it would be cleaner to just take the mutex at the top
> and unlock it after the out label to which all the existing goto-s
> already go ?
>
I did consider that - and it was in my first implementation; but then I got concerned
about if the mutex_unlock could potentially get called without mutex_lock having been
called beforehand. I couldn't find any good reference as to whether that was safe or not.
I ended up deciding that a few extra brackets and unlock calls wasn't that ugly and was 'safer'...and
so went that route.
Happy to change it - but do you happen to know if it's safe to call unlock without a lock? If it is then
that implementation is cleaner.
Mark
