2022-11-28 06:20:20

by Duoming Zhou

Subject: [PATCH] Revert "char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol"

This reverts commit be826ada52f1fcabed5b5217c94609ebf5967211.

The function monitor_card() is a timer handler that runs in an
atomic context, but it calls usleep_range() that can sleep.
As a result, the sleep-in-atomic-context bugs will happen.
The process is shown below:

(atomic context)
monitor_card()
set_protocol()
usleep_range() //sleep

The origin commit c1986ee9bea3 ("[PATCH] New Omnikey Cardman
4000 driver") works fine.

Fixes: be826ada52f1 ("char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol")
Signed-off-by: Duoming Zhou <[email protected]>
---
drivers/char/pcmcia/cm4000_cs.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
index adaec8fd4b1..7125f89531f 100644
--- a/drivers/char/pcmcia/cm4000_cs.c
+++ b/drivers/char/pcmcia/cm4000_cs.c
@@ -529,7 +529,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
DEBUGP(5, dev, "NumRecBytes is valid\n");
break;
}
- usleep_range(10000, 11000);
+ mdelay(10);
}
if (i == 100) {
DEBUGP(5, dev, "Timeout waiting for NumRecBytes getting "
@@ -549,7 +549,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
}
break;
}
- usleep_range(10000, 11000);
+ mdelay(10);
}

/* check whether it is a short PTS reply? */
--
2.17.1

2022-12-18 13:06:01

by Greg Kroah-Hartman

Subject: Re: [PATCH] Revert "char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol"

On Mon, Nov 28, 2022 at 01:39:15PM +0800, Duoming Zhou wrote:
> This reverts commit be826ada52f1fcabed5b5217c94609ebf5967211.
>
> The function monitor_card() is a timer handler that runs in an
> atomic context, but it calls usleep_range() that can sleep.
> As a result, the sleep-in-atomic-context bugs will happen.
> The process is shown below:
>
> (atomic context)
> monitor_card()
> set_protocol()
> usleep_range() //sleep
>
> The origin commit c1986ee9bea3 ("[PATCH] New Omnikey Cardman
> 4000 driver") works fine.
>
> Fixes: be826ada52f1 ("char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol")
> Signed-off-by: Duoming Zhou <[email protected]>
> ---
> drivers/char/pcmcia/cm4000_cs.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
> index adaec8fd4b1..7125f89531f 100644
> --- a/drivers/char/pcmcia/cm4000_cs.c
> +++ b/drivers/char/pcmcia/cm4000_cs.c
> @@ -529,7 +529,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
> DEBUGP(5, dev, "NumRecBytes is valid\n");
> break;
> }
> - usleep_range(10000, 11000);
> + mdelay(10);
> }
> if (i == 100) {
> DEBUGP(5, dev, "Timeout waiting for NumRecBytes getting "
> @@ -549,7 +549,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
> }
> break;
> }
> - usleep_range(10000, 11000);
> + mdelay(10);

Can you add a comment that says "can not sleep as this is atomic
context" for these calls so that this doesn't get changed again in the
future?

thanks,

greg k-h

2022-12-18 13:34:39

by Duoming Zhou

Subject: Re: [PATCH] Revert "char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol"

Hello,

On Sun, 18 Dec 2022 12:43:27 +0100 Greg KH wrote:

> On Mon, Nov 28, 2022 at 01:39:15PM +0800, Duoming Zhou wrote:
> > This reverts commit be826ada52f1fcabed5b5217c94609ebf5967211.
> >
> > The function monitor_card() is a timer handler that runs in an
> > atomic context, but it calls usleep_range() that can sleep.
> > As a result, the sleep-in-atomic-context bugs will happen.
> > The process is shown below:
> >
> > (atomic context)
> > monitor_card()
> > set_protocol()
> > usleep_range() //sleep
> >
> > The origin commit c1986ee9bea3 ("[PATCH] New Omnikey Cardman
> > 4000 driver") works fine.
> >
> > Fixes: be826ada52f1 ("char: pcmcia: cm4000_cs: Replace mdelay with usleep_range in set_protocol")
> > Signed-off-by: Duoming Zhou <[email protected]>
> > ---
> > drivers/char/pcmcia/cm4000_cs.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
> > index adaec8fd4b1..7125f89531f 100644
> > --- a/drivers/char/pcmcia/cm4000_cs.c
> > +++ b/drivers/char/pcmcia/cm4000_cs.c
> > @@ -529,7 +529,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
> > DEBUGP(5, dev, "NumRecBytes is valid\n");
> > break;
> > }
> > - usleep_range(10000, 11000);
> > + mdelay(10);
> > }
> > if (i == 100) {
> > DEBUGP(5, dev, "Timeout waiting for NumRecBytes getting "
> > @@ -549,7 +549,7 @@ static int set_protocol(struct cm4000_dev *dev, struct ptsreq *ptsreq)
> > }
> > break;
> > }
> > - usleep_range(10000, 11000);
> > + mdelay(10);
>
> Can you add a comment that says "can not sleep as this is atomic
> context" for these calls so that this doesn't get changed again in the
> future?

Thank you for your reply and suggestions! I will add the comment and re-send this patch.

Best regards,
Duoming Zhou