[PATCH] wan: dscc4: use msecs_to_jiffies for conversions

[PATCH] wan: dscc4: use msecs_to_jiffies for conversions

[Nicholas Mc Guire]

API compliance scanning with coccinelle flagged:
./drivers/net/wan/dscc4.c:1036:1-33:
        WARNING: timeout (10) seems HZ dependent
./drivers/net/wan/dscc4.c:554:2-34:
        WARNING: timeout (10) seems HZ dependent
./drivers/net/wan/dscc4.c:599:2-34:
        WARNING: timeout (10) seems HZ dependent

Numeric constants passed to schedule_timeout_*() make the effective
timeout HZ dependent which does not seem to be the intent here.
Fixed up by converting the constant to jiffies with msecs_to_jiffies()

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
---

As the intended timeout is not documented and msecs_to_jiffies(10) may
be a factor 10 off from constant 10, this needs to be checked by 
someone that knows the details of this driver, in any case it should
be passed in a HZ independent way.

Patch was compile tested with x86_64_defconfig + CONFIG_WAN=y
CONFIG_HDLC=m, CONFIG_DSCC4=m

Patch is against 4.1-rc6 (localversion-next is -next-20150605)

 drivers/net/wan/dscc4.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wan/dscc4.c b/drivers/net/wan/dscc4.c
index 0822356..2ce5249 100644
--- a/drivers/net/wan/dscc4.c
+++ b/drivers/net/wan/dscc4.c
@@ -551,7 +551,7 @@ static int dscc4_wait_ack_cec(struct dscc4_dev_priv *dpriv,
 			       msg, i);
 			goto done;
 		}
-		schedule_timeout_uninterruptible(10);
+		schedule_timeout_uninterruptible(msecs_to_jiffies(10));
 		rmb();
 	} while (++i > 0);
 	netdev_err(dev, "%s timeout\n", msg);
@@ -596,7 +596,7 @@ static inline int dscc4_xpr_ack(struct dscc4_dev_priv *dpriv)
 		    (dpriv->iqtx[cur] & cpu_to_le32(Xpr)))
 			break;
 		smp_rmb();
-		schedule_timeout_uninterruptible(10);
+		schedule_timeout_uninterruptible(msecs_to_jiffies(10));
 	} while (++i > 0);
 
 	return (i >= 0 ) ? i : -EAGAIN;
@@ -1033,7 +1033,7 @@ static void dscc4_pci_reset(struct pci_dev *pdev, void __iomem *ioaddr)
 	/* Flush posted writes */
 	readl(ioaddr + GSTAR);
 
-	schedule_timeout_uninterruptible(10);
+	schedule_timeout_uninterruptible(msecs_to_jiffies(10));
 
 	for (i = 0; i < 16; i++)
 		pci_write_config_dword(pdev, i << 2, dscc4_pci_config_store[i]);
-- 
1.7.10.4

Re: [PATCH] wan: dscc4: use msecs_to_jiffies for conversions

[David Miller]

From: Nicholas Mc Guire <hofrat@osadl.org>
Date: Sat,  6 Jun 2015 10:41:06 +0200

> API compliance scanning with coccinelle flagged:
> ./drivers/net/wan/dscc4.c:1036:1-33:
>         WARNING: timeout (10) seems HZ dependent
> ./drivers/net/wan/dscc4.c:554:2-34:
>         WARNING: timeout (10) seems HZ dependent
> ./drivers/net/wan/dscc4.c:599:2-34:
>         WARNING: timeout (10) seems HZ dependent
> 
> Numeric constants passed to schedule_timeout_*() make the effective
> timeout HZ dependent which does not seem to be the intent here.
> Fixed up by converting the constant to jiffies with msecs_to_jiffies()
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>

Whoever wrote these things probably wanted whatever this amounts
to when HZ=100, so that is the only valid transformation you can
make to fix this up here.

Otherwise you seriously risk breaking the driver.

Re: [PATCH] wan: dscc4: use msecs_to_jiffies for conversions

[Nicholas Mc Guire]

On Sun, 07 Jun 2015, David Miller wrote:

> From: Nicholas Mc Guire <hofrat@osadl.org>
> Date: Sat,  6 Jun 2015 10:41:06 +0200
> 
> > API compliance scanning with coccinelle flagged:
> > ./drivers/net/wan/dscc4.c:1036:1-33:
> >         WARNING: timeout (10) seems HZ dependent
> > ./drivers/net/wan/dscc4.c:554:2-34:
> >         WARNING: timeout (10) seems HZ dependent
> > ./drivers/net/wan/dscc4.c:599:2-34:
> >         WARNING: timeout (10) seems HZ dependent
> > 
> > Numeric constants passed to schedule_timeout_*() make the effective
> > timeout HZ dependent which does not seem to be the intent here.
> > Fixed up by converting the constant to jiffies with msecs_to_jiffies()
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> 
> Whoever wrote these things probably wanted whatever this amounts
> to when HZ=100, so that is the only valid transformation you can
> make to fix this up here.
> 
> Otherwise you seriously risk breaking the driver.

I did not find dscc4 in the 2.2 series of kernels so it does not predate
configurable HZ - or do you mean simply that increasing the timeout
here should be side-effect free and thus the larger of the values
should be taken ? - though that would imply that it is possibly now 
broken for HZ=1000. 

Will fix it up to 10 == 100ms and fix the patch documentation.

thx!
hofrat

Re: [PATCH] wan: dscc4: use msecs_to_jiffies for conversions

[Francois Romieu]

David Miller <davem@davemloft.net> :
[...]
> Whoever wrote these things probably wanted whatever this amounts
> to when HZ=100, so that is the only valid transformation you can
> make to fix this up here.

It's linux kernel illiterate style from 13 years ago but I commented
dscc4_pci_reset.

wait_ack_cec and xpr_ack are dumb busy loops that break on short integer
sign change. Hackish hint.

> Otherwise you seriously risk breaking the driver.

How seriously is hard to tell. I've never tried it at really low line
rates though.

Please apply.

Thanks.

-- 
Ueimor