linux-kernel - Re: [PATCH] staging: rtl8188eu: replaced msleep() by usleep

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Date:   Mon, 12 Apr 2021 13:29:18 +0530
From:   Mitali Borkar <mitaliborkar810@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Larry.Finger@...inger.net, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, outreachy-kernel@...glegroups.com,
        mitali_s@...iitr.ac.in
Subject: Re: [PATCH] staging: rtl8188eu: replaced msleep() by usleep_range()

On Mon, Apr 12, 2021 at 08:19:02AM +0200, Greg KH wrote:
> On Mon, Apr 12, 2021 at 11:40:53AM +0530, Mitali Borkar wrote:
> > Fixed the warning:-msleep < 20ms can sleep for up to 20ms by replacing
> > msleep(unsigned long msecs) by usleep_range(unsigned long min, unsigned long max)
> > in usecs as msleep(1ms~20ms) can sleep for upto 20 ms.
> > 
> > Signed-off-by: Mitali Borkar <mitaliborkar810@...il.com>
> > ---
> >  drivers/staging/rtl8188eu/core/rtw_mlme_ext.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/rtl8188eu/core/rtw_mlme_ext.c b/drivers/staging/rtl8188eu/core/rtw_mlme_ext.c
> > index 50d3c3631be0..6afbb5bf8118 100644
> > --- a/drivers/staging/rtl8188eu/core/rtw_mlme_ext.c
> > +++ b/drivers/staging/rtl8188eu/core/rtw_mlme_ext.c
> > @@ -5396,7 +5396,7 @@ u8 tx_beacon_hdl(struct adapter *padapter, unsigned char *pbuf)
> >  			return H2C_SUCCESS;
> >  
> >  		if ((pstapriv->tim_bitmap & BIT(0)) && (psta_bmc->sleepq_len > 0)) {
> > -			msleep(10);/*  10ms, ATIM(HIQ) Windows */
> > +			usleep_range(10000 , 20000);/*  10ms, ATIM(HIQ) Windows */
> 
> How do you know you can sleep for 20000 here?
>

When i ran checkpatch.pl it warned that msleep<20 ms can sleep for 20ms.
I checked Documentation, it stated that msleep(1ms~20ms) will often
sleep longer, ~20ms for any value given in between 1~20ms. 

That's why I took 20msec/20000usec as max sleep value. 


> And given that you just changed how the sleep works, are you sure the
> functionality is the same now?

I am still learning, I am not sure about this.
> 
> Only change this type of warning if you have the hardware and can test
> the change properly.
> 
> thanks,
> 
> greg k-h