linux-kernel - Re: [PATCH][next] Bluetooth: use bitmap_empty to check if a bitmap has any bits set

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Message-ID: <51ce4458-cf8c-6219-e945-3333226dbdcc@canonical.com>
Date:   Thu, 7 Oct 2021 16:39:00 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] Bluetooth: use bitmap_empty to check if a bitmap
 has any bits set

On 07/10/2021 16:34, Luiz Augusto von Dentz wrote:
> Hi Colin,
> 
> On Thu, Oct 7, 2021 at 4:17 AM Colin King <colin.king@...onical.com> wrote:
>>
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> The check to see if any tasks are left checks if bitmap array is zero
>> rather than using the appropriate bitmap helper functions to check the
>> bits in the array. Fix this by using bitmap_empty on the bitmap.
>>
>> Addresses-Coverity: (" Array compared against 0")
>> Fixes: 912730b52552 ("Bluetooth: Fix wake up suspend_wait_q prematurely")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>   net/bluetooth/hci_request.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
>> index 209f4fe17237..bad3b9c895ba 100644
>> --- a/net/bluetooth/hci_request.c
>> +++ b/net/bluetooth/hci_request.c
>> @@ -1108,7 +1108,7 @@ static void suspend_req_complete(struct hci_dev *hdev, u8 status, u16 opcode)
>>          clear_bit(SUSPEND_SET_ADV_FILTER, hdev->suspend_tasks);
>>
>>          /* Wake up only if there are no tasks left */
>> -       if (!hdev->suspend_tasks)
>> +       if (!bitmap_empty(hdev->suspend_tasks, __SUSPEND_NUM_TASKS))
>>                  wake_up(&hdev->suspend_wait_q);
>>   }
>>
>> --
>> 2.32.0
> 
> I was going to revert this change since it appears wake_up does
> actually check the wake condition there is no premature wake up after
> all.
> 
OK, makes sense.

Colin