linux-kernel - Re: [PATCH v2] uwb: properly check kthread

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Message-ID: <CAAeHK+xN+xFxjR+c6RRAau1h2jpouCsu6nbr4S0Rf_sYDhJg=g@mail.gmail.com>
Date:   Thu, 14 Sep 2017 14:31:25 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>,
        "Gustavo A . R . Silva" <garsilva@...eddedor.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kostya Serebryany <kcc@...gle.com>
Subject: Re: [PATCH v2] uwb: properly check kthread_run return value

On Wed, Sep 13, 2017 at 6:53 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> On Wed, Sep 13, 2017 at 6:06 PM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
>> uwbd_start() calls kthread_run() and checks that the return value is
>> not NULL. But the return value is not NULL in case kthread_run() fails,
>> it takes the form of ERR_PTR(-EINTR).
>>
>> Use IS_ERR() instead.
>>
>> Also add a check to uwbd_stop().
>>
>> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
>> ---
>>  drivers/uwb/uwbd.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/uwb/uwbd.c b/drivers/uwb/uwbd.c
>> index 01c20a260a8b..2a3cc48d837c 100644
>> --- a/drivers/uwb/uwbd.c
>> +++ b/drivers/uwb/uwbd.c
>> @@ -303,7 +303,7 @@ static int uwbd(void *param)
>>  void uwbd_start(struct uwb_rc *rc)
>>  {
>>         rc->uwbd.task = kthread_run(uwbd, rc, "uwbd");
>> -       if (rc->uwbd.task == NULL)
>> +       if (IS_ERR(rc->uwbd.task))
>>                 printk(KERN_ERR "UWB: Cannot start management daemon; "
>>                        "UWB won't work\n");
>>         else
>> @@ -313,7 +313,8 @@ void uwbd_start(struct uwb_rc *rc)
>>  /* Stop the UWB daemon and free any unprocessed events */
>>  void uwbd_stop(struct uwb_rc *rc)
>>  {
>> -       kthread_stop(rc->uwbd.task);
>> +       if (!IS_ERR(rc->uwbd.task))
>> +               kthread_stop(rc->uwbd.task);
>
> It looks weird to assign an error to rc->uwbd.task and leave it there.
> I think it's better to not assign errors to rc->uwbd.task, i.e. it's
> either a valid task or NULL.

Sent v3.

>
>>         uwbd_flush(rc);
>>  }
>>
>> --
>> 2.14.1.581.gf28d330327-goog
>>