* Re: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 1:51 [PATCH net] net: fec: avoid lock evasion when reading pps_enable Wei Fang
@ 2024-05-13 7:29 ` Eric Dumazet
2024-05-13 7:53 ` Wei Fang
2024-05-13 9:27 ` Hariprasad Kelam
2024-05-13 19:54 ` Simon Horman
2 siblings, 1 reply; 10+ messages in thread
From: Eric Dumazet @ 2024-05-13 7:29 UTC (permalink / raw)
To: Wei Fang
Cc: davem, kuba, pabeni, shenwei.wang, xiaoning.wang, richardcochran,
andrew, netdev, linux-kernel, imx
On Mon, May 13, 2024 at 4:02 AM Wei Fang <wei.fang@nxp•com> wrote:
>
> The assignment of pps_enable is protected by tmreg_lock, but the read
> operation of pps_enable is not. So the Coverity tool reports a lock
> evasion warning which may cause data race to occur when running in a
> multithread environment. Although this issue is almost impossible to
> occur, we'd better fix it, at least it seems more logically reasonable,
> and it also prevents Coverity from continuing to issue warnings.
>
> Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp clock")
> Signed-off-by: Wei Fang <wei.fang@nxp•com>
> ---
> drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
> index 181d9bfbee22..8d37274a3fb0 100644
> --- a/drivers/net/ethernet/freescale/fec_ptp.c
> +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct fec_enet_private *fep, uint enable)
> struct timespec64 ts;
> u64 ns;
>
> - if (fep->pps_enable == enable)
> - return 0;
> -
> fep->pps_channel = DEFAULT_PPS_CHANNEL;
> fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
Why are these writes left without the spinlock protection ?
>
> spin_lock_irqsave(&fep->tmreg_lock, flags);
>
> + if (fep->pps_enable == enable) {
> + spin_unlock_irqrestore(&fep->tmreg_lock, flags);
> + return 0;
> + }
> +
> if (enable) {
> /* clear capture or output compare interrupt status if have.
> */
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 10+ messages in thread* RE: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 7:29 ` Eric Dumazet
@ 2024-05-13 7:53 ` Wei Fang
2024-05-13 8:40 ` Eric Dumazet
0 siblings, 1 reply; 10+ messages in thread
From: Wei Fang @ 2024-05-13 7:53 UTC (permalink / raw)
To: Eric Dumazet
Cc: davem@davemloft•net, kuba@kernel•org, pabeni@redhat•com,
Shenwei Wang, Clark Wang, richardcochran@gmail•com,
andrew@lunn•ch, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org, imx@lists•linux.dev
> -----Original Message-----
> From: Eric Dumazet <edumazet@google•com>
> Sent: 2024年5月13日 15:29
> To: Wei Fang <wei.fang@nxp•com>
> Cc: davem@davemloft•net; kuba@kernel•org; pabeni@redhat•com; Shenwei
> Wang <shenwei.wang@nxp•com>; Clark Wang <xiaoning.wang@nxp•com>;
> richardcochran@gmail•com; andrew@lunn•ch; netdev@vger•kernel.org;
> linux-kernel@vger•kernel.org; imx@lists•linux.dev
> Subject: Re: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
>
> On Mon, May 13, 2024 at 4:02 AM Wei Fang <wei.fang@nxp•com> wrote:
> >
> > The assignment of pps_enable is protected by tmreg_lock, but the read
> > operation of pps_enable is not. So the Coverity tool reports a lock
> > evasion warning which may cause data race to occur when running in a
> > multithread environment. Although this issue is almost impossible to
> > occur, we'd better fix it, at least it seems more logically
> > reasonable, and it also prevents Coverity from continuing to issue warnings.
> >
> > Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp
> > clock")
> > Signed-off-by: Wei Fang <wei.fang@nxp•com>
> > ---
> > drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > b/drivers/net/ethernet/freescale/fec_ptp.c
> > index 181d9bfbee22..8d37274a3fb0 100644
> > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct
> fec_enet_private *fep, uint enable)
> > struct timespec64 ts;
> > u64 ns;
> >
> > - if (fep->pps_enable == enable)
> > - return 0;
> > -
> > fep->pps_channel = DEFAULT_PPS_CHANNEL;
> > fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
>
> Why are these writes left without the spinlock protection ?
For fec driver, the pps_channel and the reload_period of PPS request
are always fixed, and they were also not protected by the lock in the
original code.
>
>
> >
> > spin_lock_irqsave(&fep->tmreg_lock, flags);
> >
> > + if (fep->pps_enable == enable) {
> > + spin_unlock_irqrestore(&fep->tmreg_lock, flags);
> > + return 0;
> > + }
> > +
> > if (enable) {
> > /* clear capture or output compare interrupt status if
> have.
> > */
> > --
> > 2.34.1
> >
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 7:53 ` Wei Fang
@ 2024-05-13 8:40 ` Eric Dumazet
2024-05-13 12:18 ` Wei Fang
0 siblings, 1 reply; 10+ messages in thread
From: Eric Dumazet @ 2024-05-13 8:40 UTC (permalink / raw)
To: Wei Fang
Cc: davem@davemloft•net, kuba@kernel•org, pabeni@redhat•com,
Shenwei Wang, Clark Wang, richardcochran@gmail•com,
andrew@lunn•ch, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org, imx@lists•linux.dev
On Mon, May 13, 2024 at 9:53 AM Wei Fang <wei.fang@nxp•com> wrote:
>
> > -----Original Message-----
> > From: Eric Dumazet <edumazet@google•com>
> > Sent: 2024年5月13日 15:29
> > To: Wei Fang <wei.fang@nxp•com>
> > Cc: davem@davemloft•net; kuba@kernel•org; pabeni@redhat•com; Shenwei
> > Wang <shenwei.wang@nxp•com>; Clark Wang <xiaoning.wang@nxp•com>;
> > richardcochran@gmail•com; andrew@lunn•ch; netdev@vger•kernel.org;
> > linux-kernel@vger•kernel.org; imx@lists•linux.dev
> > Subject: Re: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
> >
> > On Mon, May 13, 2024 at 4:02 AM Wei Fang <wei.fang@nxp•com> wrote:
> > >
> > > The assignment of pps_enable is protected by tmreg_lock, but the read
> > > operation of pps_enable is not. So the Coverity tool reports a lock
> > > evasion warning which may cause data race to occur when running in a
> > > multithread environment. Although this issue is almost impossible to
> > > occur, we'd better fix it, at least it seems more logically
> > > reasonable, and it also prevents Coverity from continuing to issue warnings.
> > >
> > > Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp
> > > clock")
> > > Signed-off-by: Wei Fang <wei.fang@nxp•com>
> > > ---
> > > drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > > b/drivers/net/ethernet/freescale/fec_ptp.c
> > > index 181d9bfbee22..8d37274a3fb0 100644
> > > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > > @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct
> > fec_enet_private *fep, uint enable)
> > > struct timespec64 ts;
> > > u64 ns;
> > >
> > > - if (fep->pps_enable == enable)
> > > - return 0;
> > > -
> > > fep->pps_channel = DEFAULT_PPS_CHANNEL;
> > > fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
> >
> > Why are these writes left without the spinlock protection ?
> For fec driver, the pps_channel and the reload_period of PPS request
> are always fixed, and they were also not protected by the lock in the
> original code.
If this is the case, please move this initialization elsewhere, so
that we can be absolutely sure of the claim.
I see fep->reload_period being overwritten in this file, I do not see
clear evidence this is all safe.
^ permalink raw reply [flat|nested] 10+ messages in thread* RE: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 8:40 ` Eric Dumazet
@ 2024-05-13 12:18 ` Wei Fang
0 siblings, 0 replies; 10+ messages in thread
From: Wei Fang @ 2024-05-13 12:18 UTC (permalink / raw)
To: Eric Dumazet
Cc: davem@davemloft•net, kuba@kernel•org, pabeni@redhat•com,
Shenwei Wang, Clark Wang, richardcochran@gmail•com,
andrew@lunn•ch, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org, imx@lists•linux.dev
> -----Original Message-----
> From: Eric Dumazet <edumazet@google•com>
> Sent: 2024年5月13日 16:41
> To: Wei Fang <wei.fang@nxp•com>
> Cc: davem@davemloft•net; kuba@kernel•org; pabeni@redhat•com; Shenwei
> Wang <shenwei.wang@nxp•com>; Clark Wang <xiaoning.wang@nxp•com>;
> richardcochran@gmail•com; andrew@lunn•ch; netdev@vger•kernel.org;
> linux-kernel@vger•kernel.org; imx@lists•linux.dev
> Subject: Re: [PATCH net] net: fec: avoid lock evasion when reading
> pps_enable
>
> On Mon, May 13, 2024 at 9:53 AM Wei Fang <wei.fang@nxp•com> wrote:
> >
> > > -----Original Message-----
> > > From: Eric Dumazet <edumazet@google•com>
> > > Sent: 2024年5月13日 15:29
> > > To: Wei Fang <wei.fang@nxp•com>
> > > Cc: davem@davemloft•net; kuba@kernel•org; pabeni@redhat•com;
> Shenwei
> > > Wang <shenwei.wang@nxp•com>; Clark Wang
> <xiaoning.wang@nxp•com>;
> > > richardcochran@gmail•com; andrew@lunn•ch; netdev@vger•kernel.org;
> > > linux-kernel@vger•kernel.org; imx@lists•linux.dev
> > > Subject: Re: [PATCH net] net: fec: avoid lock evasion when reading
> > > pps_enable
> > >
> > > On Mon, May 13, 2024 at 4:02 AM Wei Fang <wei.fang@nxp•com>
> wrote:
> > > >
> > > > The assignment of pps_enable is protected by tmreg_lock, but the
> > > > read operation of pps_enable is not. So the Coverity tool reports
> > > > a lock evasion warning which may cause data race to occur when
> > > > running in a multithread environment. Although this issue is
> > > > almost impossible to occur, we'd better fix it, at least it seems
> > > > more logically reasonable, and it also prevents Coverity from continuing
> to issue warnings.
> > > >
> > > > Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on
> > > > ptp
> > > > clock")
> > > > Signed-off-by: Wei Fang <wei.fang@nxp•com>
> > > > ---
> > > > drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> > > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > > > b/drivers/net/ethernet/freescale/fec_ptp.c
> > > > index 181d9bfbee22..8d37274a3fb0 100644
> > > > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > > > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > > > @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct
> > > fec_enet_private *fep, uint enable)
> > > > struct timespec64 ts;
> > > > u64 ns;
> > > >
> > > > - if (fep->pps_enable == enable)
> > > > - return 0;
> > > > -
> > > > fep->pps_channel = DEFAULT_PPS_CHANNEL;
> > > > fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
> > >
> > > Why are these writes left without the spinlock protection ?
> > For fec driver, the pps_channel and the reload_period of PPS request
> > are always fixed, and they were also not protected by the lock in the
> > original code.
>
> If this is the case, please move this initialization elsewhere, so that we can be
> absolutely sure of the claim.
>
Accept, thanks
> I see fep->reload_period being overwritten in this file, I do not see clear
> evidence this is all safe.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 1:51 [PATCH net] net: fec: avoid lock evasion when reading pps_enable Wei Fang
2024-05-13 7:29 ` Eric Dumazet
@ 2024-05-13 9:27 ` Hariprasad Kelam
2024-05-13 12:24 ` Wei Fang
2024-05-13 19:54 ` Simon Horman
2 siblings, 1 reply; 10+ messages in thread
From: Hariprasad Kelam @ 2024-05-13 9:27 UTC (permalink / raw)
To: Wei Fang, davem@davemloft•net, edumazet@google•com,
kuba@kernel•org, pabeni@redhat•com, shenwei.wang@nxp•com,
xiaoning.wang@nxp•com, richardcochran@gmail•com, andrew@lunn•ch,
netdev@vger•kernel.org
Cc: linux-kernel@vger•kernel.org, imx@lists•linux.dev
See inline,
> The assignment of pps_enable is protected by tmreg_lock, but the read
> operation of pps_enable is not. So the Coverity tool reports a lock evasion
> warning which may cause data race to occur when running in a multithread
> environment. Although this issue is almost impossible to occur, we'd better fix
> it, at least it seems more logically reasonable, and it also prevents Coverity
> from continuing to issue warnings.
>
> Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp clock")
> Signed-off-by: Wei Fang <wei.fang@nxp•com>
> ---
> drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> b/drivers/net/ethernet/freescale/fec_ptp.c
> index 181d9bfbee22..8d37274a3fb0 100644
> --- a/drivers/net/ethernet/freescale/fec_ptp.c
> +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct
> fec_enet_private *fep, uint enable)
> struct timespec64 ts;
> u64 ns;
>
> - if (fep->pps_enable == enable)
> - return 0;
> -
> fep->pps_channel = DEFAULT_PPS_CHANNEL;
> fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
>
> spin_lock_irqsave(&fep->tmreg_lock, flags);
>
> + if (fep->pps_enable == enable) {
Can we atomic_set/get instead of spin_lock here.
Thanks,
Hariprasad k
> + spin_unlock_irqrestore(&fep->tmreg_lock, flags);
> + return 0;
> + }
> +
> if (enable) {
> /* clear capture or output compare interrupt status if have.
> */
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 10+ messages in thread* RE: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 9:27 ` Hariprasad Kelam
@ 2024-05-13 12:24 ` Wei Fang
2024-05-14 9:26 ` Hariprasad Kelam
0 siblings, 1 reply; 10+ messages in thread
From: Wei Fang @ 2024-05-13 12:24 UTC (permalink / raw)
To: Hariprasad Kelam, davem@davemloft•net, edumazet@google•com,
kuba@kernel•org, pabeni@redhat•com, Shenwei Wang, Clark Wang,
richardcochran@gmail•com, andrew@lunn•ch, netdev@vger•kernel.org
Cc: linux-kernel@vger•kernel.org, imx@lists•linux.dev
> -----Original Message-----
> From: Hariprasad Kelam <hkelam@marvell•com>
> Sent: 2024年5月13日 17:27
> To: Wei Fang <wei.fang@nxp•com>; davem@davemloft•net;
> edumazet@google•com; kuba@kernel•org; pabeni@redhat•com; Shenwei
> Wang <shenwei.wang@nxp•com>; Clark Wang <xiaoning.wang@nxp•com>;
> richardcochran@gmail•com; andrew@lunn•ch; netdev@vger•kernel.org
> Cc: linux-kernel@vger•kernel.org; imx@lists•linux.dev
> Subject: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
>
> See inline,
>
> > The assignment of pps_enable is protected by tmreg_lock, but the read
> > operation of pps_enable is not. So the Coverity tool reports a lock
> > evasion warning which may cause data race to occur when running in a
> > multithread environment. Although this issue is almost impossible to
> > occur, we'd better fix it, at least it seems more logically
> > reasonable, and it also prevents Coverity from continuing to issue warnings.
> >
> > Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp
> > clock")
> > Signed-off-by: Wei Fang <wei.fang@nxp•com>
> > ---
> > drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > b/drivers/net/ethernet/freescale/fec_ptp.c
> > index 181d9bfbee22..8d37274a3fb0 100644
> > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct
> > fec_enet_private *fep, uint enable)
> > struct timespec64 ts;
> > u64 ns;
> >
> > - if (fep->pps_enable == enable)
> > - return 0;
> > -
> > fep->pps_channel = DEFAULT_PPS_CHANNEL;
> > fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
> >
> > spin_lock_irqsave(&fep->tmreg_lock, flags);
> >
> > + if (fep->pps_enable == enable) {
>
> Can we atomic_set/get instead of spin_lock here.
>
I'm afraid that cannot eliminate the lock evasion warning, because
it's still possible that multithreads take the false branch of
"if (fep->pps_enable == enable)" before pps_enable is updated.
> Thanks,
> Hariprasad k
> > + spin_unlock_irqrestore(&fep->tmreg_lock, flags);
> > + return 0;
> > + }
> > +
> > if (enable) {
> > /* clear capture or output compare interrupt status if have.
> > */
> > --
> > 2.34.1
> >
^ permalink raw reply [flat|nested] 10+ messages in thread* RE: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 12:24 ` Wei Fang
@ 2024-05-14 9:26 ` Hariprasad Kelam
0 siblings, 0 replies; 10+ messages in thread
From: Hariprasad Kelam @ 2024-05-14 9:26 UTC (permalink / raw)
To: Wei Fang, davem@davemloft•net, edumazet@google•com,
kuba@kernel•org, pabeni@redhat•com, Shenwei Wang, Clark Wang,
richardcochran@gmail•com, andrew@lunn•ch, netdev@vger•kernel.org
Cc: linux-kernel@vger•kernel.org, imx@lists•linux.dev
> > -----Original Message-----
> > From: Hariprasad Kelam <hkelam@marvell•com>
> > Sent: 2024年5月13日 17:27
> > To: Wei Fang <wei.fang@nxp•com>; davem@davemloft•net;
> > edumazet@google•com; kuba@kernel•org; pabeni@redhat•com; Shenwei
> Wang
> > <shenwei.wang@nxp•com>; Clark Wang <xiaoning.wang@nxp•com>;
> > richardcochran@gmail•com; andrew@lunn•ch; netdev@vger•kernel.org
> > Cc: linux-kernel@vger•kernel.org; imx@lists•linux.dev
> > Subject: [PATCH net] net: fec: avoid lock evasion when reading
> > pps_enable
> >
> > See inline,
> >
> > > The assignment of pps_enable is protected by tmreg_lock, but the
> > > read operation of pps_enable is not. So the Coverity tool reports a
> > > lock evasion warning which may cause data race to occur when running
> > > in a multithread environment. Although this issue is almost
> > > impossible to occur, we'd better fix it, at least it seems more
> > > logically reasonable, and it also prevents Coverity from continuing to issue
> warnings.
> > >
> > > Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp
> > > clock")
> > > Signed-off-by: Wei Fang <wei.fang@nxp•com>
> > > ---
> > > drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
> > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > > b/drivers/net/ethernet/freescale/fec_ptp.c
> > > index 181d9bfbee22..8d37274a3fb0 100644
> > > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > > @@ -104,14 +104,16 @@ static int fec_ptp_enable_pps(struct
> > > fec_enet_private *fep, uint enable)
> > > struct timespec64 ts;
> > > u64 ns;
> > >
> > > - if (fep->pps_enable == enable)
> > > - return 0;
> > > -
> > > fep->pps_channel = DEFAULT_PPS_CHANNEL;
> > > fep->reload_period = PPS_OUPUT_RELOAD_PERIOD;
> > >
> > > spin_lock_irqsave(&fep->tmreg_lock, flags);
> > >
> > > + if (fep->pps_enable == enable) {
> >
> > Can we atomic_set/get instead of spin_lock here.
> >
> I'm afraid that cannot eliminate the lock evasion warning, because it's still
> possible that multithreads take the false branch of "if (fep->pps_enable ==
> enable)" before pps_enable is updated.
>
> Since in fec_ptp_enable_pps(), value of pps_enable is checked before entering the actual code changes,
Better approach is to use atomic_read/write. This is not only for reading but for assigning the values as well.
This way covertity wont complain.
> > Thanks,
> > Hariprasad k
> > > + spin_unlock_irqrestore(&fep->tmreg_lock, flags);
> > > + return 0;
> > > + }
> > > +
> > > if (enable) {
> > > /* clear capture or output compare interrupt status if have.
> > > */
> > > --
> > > 2.34.1
> > >
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 1:51 [PATCH net] net: fec: avoid lock evasion when reading pps_enable Wei Fang
2024-05-13 7:29 ` Eric Dumazet
2024-05-13 9:27 ` Hariprasad Kelam
@ 2024-05-13 19:54 ` Simon Horman
2024-05-13 19:56 ` Simon Horman
2 siblings, 1 reply; 10+ messages in thread
From: Simon Horman @ 2024-05-13 19:54 UTC (permalink / raw)
To: Wei Fang
Cc: davem, edumazet, kuba, pabeni, shenwei.wang, xiaoning.wang,
richardcochran, andrew, netdev, linux-kernel, imx
On Mon, May 13, 2024 at 09:51:26AM +0800, Wei Fang wrote:
> The assignment of pps_enable is protected by tmreg_lock, but the read
> operation of pps_enable is not. So the Coverity tool reports a lock
> evasion warning which may cause data race to occur when running in a
> multithread environment. Although this issue is almost impossible to
> occur, we'd better fix it, at least it seems more logically reasonable,
> and it also prevents Coverity from continuing to issue warnings.
>
> Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp clock")
> Signed-off-by: Wei Fang <wei.fang@nxp•com>
Reviewed-by: Simon Horman <horms@kernel•org>
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH net] net: fec: avoid lock evasion when reading pps_enable
2024-05-13 19:54 ` Simon Horman
@ 2024-05-13 19:56 ` Simon Horman
0 siblings, 0 replies; 10+ messages in thread
From: Simon Horman @ 2024-05-13 19:56 UTC (permalink / raw)
To: Wei Fang
Cc: davem, edumazet, kuba, pabeni, shenwei.wang, xiaoning.wang,
richardcochran, andrew, netdev, linux-kernel, imx
On Mon, May 13, 2024 at 08:54:59PM +0100, Simon Horman wrote:
> On Mon, May 13, 2024 at 09:51:26AM +0800, Wei Fang wrote:
> > The assignment of pps_enable is protected by tmreg_lock, but the read
> > operation of pps_enable is not. So the Coverity tool reports a lock
> > evasion warning which may cause data race to occur when running in a
> > multithread environment. Although this issue is almost impossible to
> > occur, we'd better fix it, at least it seems more logically reasonable,
> > and it also prevents Coverity from continuing to issue warnings.
> >
> > Fixes: 278d24047891 ("net: fec: ptp: Enable PPS output based on ptp clock")
> > Signed-off-by: Wei Fang <wei.fang@nxp•com>
>
> Reviewed-by: Simon Horman <horms@kernel•org>
Sorry, I convinced myself this is correct.
But I now see that questions have been raised by others.
So please ignore the above.
^ permalink raw reply [flat|nested] 10+ messages in thread