linux-kernel - RE: [EXTERNAL] [PATCH net-next] net: fec: Convert fec driver to use lock guards

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Date: Wed, 8 May 2024 02:46:31 +0000
From: Wei Fang <wei.fang@....com>
To: Suman Ghosh <sumang@...vell.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
	"richardcochran@...il.com" <richardcochran@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [EXTERNAL] [PATCH net-next] net: fec: Convert fec driver to use
 lock guards

> -----Original Message-----
> From: Suman Ghosh <sumang@...vell.com>
> Sent: 2024年5月7日 19:55
> To: Wei Fang <wei.fang@....com>; davem@...emloft.net;
> edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; Shenwei
> Wang <shenwei.wang@....com>; Clark Wang <xiaoning.wang@....com>;
> richardcochran@...il.com; netdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org; imx@...ts.linux.dev
> Subject: RE: [EXTERNAL] [PATCH net-next] net: fec: Convert fec driver to use
> lock guards
> 
> > drivers/net/ethernet/freescale/fec_main.c |  37 ++++----
> >drivers/net/ethernet/freescale/fec_ptp.c  | 104 +++++++++-------------
> > 2 files changed, 58 insertions(+), 83 deletions(-)
> >
> >diff --git a/drivers/net/ethernet/freescale/fec_main.c
> >b/drivers/net/ethernet/freescale/fec_main.c
> >index 8bd213da8fb6..5f98c0615115 100644
> >--- a/drivers/net/ethernet/freescale/fec_main.c
> >+++ b/drivers/net/ethernet/freescale/fec_main.c
> >@@ -1397,12 +1397,11 @@ static void
> > fec_enet_hwtstamp(struct fec_enet_private *fep, unsigned ts,
> > 	struct skb_shared_hwtstamps *hwtstamps)  {
> >-	unsigned long flags;
> > 	u64 ns;
> >
> >-	spin_lock_irqsave(&fep->tmreg_lock, flags);
> >-	ns = timecounter_cyc2time(&fep->tc, ts);
> >-	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
> >+	scoped_guard(spinlock_irqsave, &fep->tmreg_lock) {
> >+		ns = timecounter_cyc2time(&fep->tc, ts);
> >+	}
> >
> > 	memset(hwtstamps, 0, sizeof(*hwtstamps));
> > 	hwtstamps->hwtstamp = ns_to_ktime(ns); @@ -2313,15 +2312,13 @@
> static
> >int fec_enet_clk_enable(struct net_device *ndev, bool enable)
> > 			return ret;
> >
> > 		if (fep->clk_ptp) {
> >-			mutex_lock(&fep->ptp_clk_mutex);
> >-			ret = clk_prepare_enable(fep->clk_ptp);
> >-			if (ret) {
> >-				mutex_unlock(&fep->ptp_clk_mutex);
> >-				goto failed_clk_ptp;
> >-			} else {
> >-				fep->ptp_clk_on = true;
> >+			scoped_guard(mutex, &fep->ptp_clk_mutex) {
> >+				ret = clk_prepare_enable(fep->clk_ptp);
> >+				if (ret)
> >+					goto failed_clk_ptp;
> >+				else
> >+					fep->ptp_clk_on = true;
> > 			}
> >-			mutex_unlock(&fep->ptp_clk_mutex);
> > 		}
> >
> > 		ret = clk_prepare_enable(fep->clk_ref); @@ -2336,10 +2333,10
> @@
> >static int fec_enet_clk_enable(struct net_device *ndev, bool enable)
> > 	} else {
> > 		clk_disable_unprepare(fep->clk_enet_out);
> > 		if (fep->clk_ptp) {
> >-			mutex_lock(&fep->ptp_clk_mutex);
> >-			clk_disable_unprepare(fep->clk_ptp);
> >-			fep->ptp_clk_on = false;
> >-			mutex_unlock(&fep->ptp_clk_mutex);
> >+			scoped_guard(mutex, &fep->ptp_clk_mutex) {
> >+				clk_disable_unprepare(fep->clk_ptp);
> >+				fep->ptp_clk_on = false;
> >+			}
> > 		}
> > 		clk_disable_unprepare(fep->clk_ref);
> > 		clk_disable_unprepare(fep->clk_2x_txclk);
> >@@ -2352,10 +2349,10 @@ static int fec_enet_clk_enable(struct
> net_device
> >*ndev, bool enable)
> > 		clk_disable_unprepare(fep->clk_ref);
> > failed_clk_ref:
> > 	if (fep->clk_ptp) {
> >-		mutex_lock(&fep->ptp_clk_mutex);
> >-		clk_disable_unprepare(fep->clk_ptp);
> >-		fep->ptp_clk_on = false;
> >-		mutex_unlock(&fep->ptp_clk_mutex);
> >+		scoped_guard(mutex, &fep->ptp_clk_mutex) {
> [Suman] Hi Wei,
> I am new to the use of scoped_guard() and have a confusion here. Above,
> "goto failed_clk_ref" is getting called after scoped_guard() declaration and
> you are again doing scoped_guard() inside the goto label failed_clk_ref. Why
> is this double declaration needed?

The lock will be freed when it goes out of scope. And the second scope_guard() is
not nested in the first scope_guard().

> >+			clk_disable_unprepare(fep->clk_ptp);
> >+			fep->ptp_clk_on = false;
> >+		}
> > 	}
> > failed_clk_ptp:
> > 	clk_disable_unprepare(fep->clk_enet_out);