The write operation to "hotplug->enabled" is protected by
the lock on line 1760, but the read operation to
this data on line 1755 is not protected by the lock.
Thus, there may exist a data race for "hotplug->enabled".
To fix this data race, the read operation to "hotplug->enabled" is
also protected by the lock.
Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/acpi/scan.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 970dd87d347c..e21d7b0f7179 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1752,11 +1752,13 @@ static struct acpi_scan_handler *acpi_scan_match_handler(const char *idstr,
void acpi_scan_hotplug_enabled(struct acpi_hotplug_profile *hotplug, bool val)
{
- if (!!hotplug->enabled == !!val)
- return;
-
mutex_lock(&acpi_scan_lock);
+ if (!!hotplug->enabled == !!val) {
+ mutex_unlock(&acpi_scan_lock);
+ return;
+ }
+
hotplug->enabled = val;
mutex_unlock(&acpi_scan_lock);
--
2.17.0
On Tue, May 8, 2018 at 5:08 AM, Jia-Ju Bai <[email protected]> wrote:
> The write operation to "hotplug->enabled" is protected by
> the lock on line 1760, but the read operation to
> this data on line 1755 is not protected by the lock.
> Thus, there may exist a data race for "hotplug->enabled".
Either it does exist, or it doesn't.
If it exists, it needs to be fixed. If it doesn't exist, nothing
needs to be done.
Which is the case?
On 2018/5/9 4:17, Rafael J. Wysocki wrote:
> On Tue, May 8, 2018 at 5:08 AM, Jia-Ju Bai <[email protected]> wrote:
>> The write operation to "hotplug->enabled" is protected by
>> the lock on line 1760, but the read operation to
>> this data on line 1755 is not protected by the lock.
>> Thus, there may exist a data race for "hotplug->enabled".
> Either it does exist, or it doesn't.
>
> If it exists, it needs to be fixed. If it doesn't exist, nothing
> needs to be done.
>
> Which is the case?
I only read the code and find this possible data race.
It is not found in real driver execution.
I am not sure of it, so I use "may" and "possible" here.
Best wishes,
Jia-Ju Bai
On Wed, May 9, 2018 at 5:17 AM, Jia-Ju Bai <[email protected]> wrote:
>
>
> On 2018/5/9 4:17, Rafael J. Wysocki wrote:
>>
>> On Tue, May 8, 2018 at 5:08 AM, Jia-Ju Bai <[email protected]> wrote:
>>>
>>> The write operation to "hotplug->enabled" is protected by
>>> the lock on line 1760, but the read operation to
>>> this data on line 1755 is not protected by the lock.
>>> Thus, there may exist a data race for "hotplug->enabled".
>>
>> Either it does exist, or it doesn't.
>>
>> If it exists, it needs to be fixed. If it doesn't exist, nothing
>> needs to be done.
>>
>> Which is the case?
>
>
> I only read the code and find this possible data race.
> It is not found in real driver execution.
> I am not sure of it, so I use "may" and "possible" here.
It looks like you are not actually sure what you are doing then.