Re: [PATCH V2 1/2] bdisp: Fix a possible sleep-in-atomic bug in bdisp_hw_reset

[Jia-Ju Bai]

On 2017/12/19 18:43, Fabien DESSENNE wrote:
> Hi,
>
>
> On 16/12/17 12:54, Jia-Ju Bai wrote:
> > The driver may sleep under a spinlock.
> > The function call path is:
> > bdisp_device_run (acquire the spinlock)
> >     bdisp_hw_reset
> >       msleep --> may sleep
> >
> > To fix it, readl_poll_timeout_atomic is used to replace msleep.
> >
> > This bug is found by my static analysis tool(DSAC) and
> > checked by my code review.
> >
> > Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
> > ---
> >    drivers/media/platform/sti/bdisp/bdisp-hw.c |   16 ++++++++--------
> >    1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/media/platform/sti/bdisp/bdisp-hw.c b/drivers/media/platform/sti/bdisp/bdisp-hw.c
> > index b7892f3..e94a371 100644
> > --- a/drivers/media/platform/sti/bdisp/bdisp-hw.c
> > +++ b/drivers/media/platform/sti/bdisp/bdisp-hw.c
> > @@ -5,6 +5,7 @@
> >     */
> >    
> >    #include <linux/delay.h>
> This delay.h include is no more needed, remove it.
>
> > +#include <linux/iopoll.h>
> >    
> >    #include "bdisp.h"
> >    #include "bdisp-filter.h"
> > @@ -366,7 +367,7 @@ struct bdisp_filter_addr {
> >     */
> >    int bdisp_hw_reset(struct bdisp_dev *bdisp)
> >    {
> > -	unsigned int i;
> > +	u32 tmp;
> >    
> >    	dev_dbg(bdisp->dev, "%s\n", __func__);
> >    
> > @@ -379,15 +380,14 @@ int bdisp_hw_reset(struct bdisp_dev *bdisp)
> >    	writel(0, bdisp->regs + BLT_CTL);
> >    
> >    	/* Wait for reset done */
> > -	for (i = 0; i < POLL_RST_MAX; i++) {
> > -		if (readl(bdisp->regs + BLT_STA1) & BLT_STA1_IDLE)
> > -			break;
> > -		msleep(POLL_RST_DELAY_MS);
> > -	}
> > -	if (i == POLL_RST_MAX)
> As recommended by Mauro, please add this comment:
> Despite the large timeout, most of the time the reset happens without
> needing any delays
>
> > +	if (readl_poll_timeout_atomic(bdisp->regs + BLT_STA1, tmp,
> > +		(tmp & BLT_STA1_IDLE), POLL_RST_DELAY_MS,
> > +			POLL_RST_DELAY_MS * POLL_RST_MAX)) {
> read_poll_timeout expects US timings, not MS.
>
> >    		dev_err(bdisp->dev, "Reset timeout\n");
> > +		return -EAGAIN;
> > +	}
> >    
> > -	return (i == POLL_RST_MAX) ? -EAGAIN : 0;
> > +	return 0;
> >    }
> >    
> >    /**

Hi,

Okay, I have submitted a new patch according to your advice :)


Thanks,
Jia-Ju Bai