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From: Jakub Kicinski <kuba@kernel.org>
To: Tan Tee Min <tee.min.tan@linux.intel.com>
Cc: Richard Cochran <richardcochran@gmail.com>,
	Tan Tee Min <tee.min.tan@intel.com>,
	Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S . Miller" <davem@davemloft.net>,
	Paolo Abeni <pabeni@redhat.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Rayagond Kokatanur <rayagond@vayavyalabs.com>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Voon Wei Feng <weifeng.voon@intel.com>,
	Wong Vee Khee <vee.khee.wong@intel.com>,
	Song Yoong Siang <yoong.siang.song@intel.com>
Subject: Re: [PATCH net 1/1] net: stmmac: add fsleep() in HW Rx timestamp checking loop
Date: Thu, 14 Apr 2022 10:42:59 +0200	[thread overview]
Message-ID: <20220414104259.0b928249@kernel.org> (raw)
In-Reply-To: <20220414072934.GA10025@linux.intel.com>

On Thu, 14 Apr 2022 15:29:34 +0800 Tan Tee Min wrote:
> > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> > > @@ -279,10 +279,11 @@ static int dwmac4_wrback_get_rx_timestamp_status(void *desc, void *next_desc,
> > >  			/* Check if timestamp is OK from context descriptor */
> > >  			do {
> > >  				ret = dwmac4_rx_check_timestamp(next_desc);
> > > -				if (ret < 0)
> > > +				if (ret <= 0)
> > >  					goto exit;
> > >  				i++;
> > >  
> > > +				fsleep(1);  
> > 
> > This is nutty.  Why isn't this code using proper deferral mechanisms
> > like work or kthread?  
> 
> Appreciate your comment.
> The dwmac4_wrback_get_rx_timestamp_status() is called by stmmac_rx()
> function which is scheduled by NAPI framework.
> Do we still need to create deferred work inside NAPI work?
> Would you mind to explain it more in detail?

fsleep() is a big hammer, can you try cpu_relax() and bumping the max
loop count a little?

WARNING: multiple messages have this Message-ID (diff)
From: Jakub Kicinski <kuba@kernel.org>
To: Tan Tee Min <tee.min.tan@linux.intel.com>
Cc: Richard Cochran <richardcochran@gmail.com>,
	Tan Tee Min <tee.min.tan@intel.com>,
	Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S . Miller" <davem@davemloft.net>,
	Paolo Abeni <pabeni@redhat.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Rayagond Kokatanur <rayagond@vayavyalabs.com>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Voon Wei Feng <weifeng.voon@intel.com>,
	Wong Vee Khee <vee.khee.wong@intel.com>,
	Song Yoong Siang <yoong.siang.song@intel.com>
Subject: Re: [PATCH net 1/1] net: stmmac: add fsleep() in HW Rx timestamp checking loop
Date: Thu, 14 Apr 2022 10:42:59 +0200	[thread overview]
Message-ID: <20220414104259.0b928249@kernel.org> (raw)
In-Reply-To: <20220414072934.GA10025@linux.intel.com>

On Thu, 14 Apr 2022 15:29:34 +0800 Tan Tee Min wrote:
> > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> > > @@ -279,10 +279,11 @@ static int dwmac4_wrback_get_rx_timestamp_status(void *desc, void *next_desc,
> > >  			/* Check if timestamp is OK from context descriptor */
> > >  			do {
> > >  				ret = dwmac4_rx_check_timestamp(next_desc);
> > > -				if (ret < 0)
> > > +				if (ret <= 0)
> > >  					goto exit;
> > >  				i++;
> > >  
> > > +				fsleep(1);  
> > 
> > This is nutty.  Why isn't this code using proper deferral mechanisms
> > like work or kthread?  
> 
> Appreciate your comment.
> The dwmac4_wrback_get_rx_timestamp_status() is called by stmmac_rx()
> function which is scheduled by NAPI framework.
> Do we still need to create deferred work inside NAPI work?
> Would you mind to explain it more in detail?

fsleep() is a big hammer, can you try cpu_relax() and bumping the max
loop count a little?

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-04-14  8:43 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-13  4:01 [PATCH net 1/1] net: stmmac: add fsleep() in HW Rx timestamp checking loop Tan Tee Min
2022-04-13  4:01 ` Tan Tee Min
2022-04-13 12:59 ` Richard Cochran
2022-04-13 12:59   ` Richard Cochran
2022-04-14  7:29   ` Tan Tee Min
2022-04-14  7:29     ` Tan Tee Min
2022-04-14  8:42     ` Jakub Kicinski [this message]
2022-04-14  8:42       ` Jakub Kicinski
2022-04-19  0:52       ` Tan Tee Min
2022-04-19  0:52         ` Tan Tee Min
2022-04-19 13:28         ` Richard Cochran
2022-04-19 13:28           ` Richard Cochran
2022-04-20  5:15           ` Tan Tee Min
2022-04-20  5:15             ` Tan Tee Min
2022-04-20 12:54             ` Richard Cochran
2022-04-20 12:54               ` Richard Cochran

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