| Message ID | 20220706105044.8071-1-paskripkin@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v3] net: ocelot: fix wrong time_after usage | expand |
Hi Pavel, On Wed, Jul 06, 2022 at 01:50:44PM +0300, Pavel Skripkin wrote: > Accidentally noticed, that this driver is the only user of > while (time_after(jiffies...)). > > It looks like typo, because likely this while loop will finish after 1st > iteration, because time_after() returns true when 1st argument _is after_ > 2nd one. > > There is one possible problem with this poll loop: the scheduler could put > the thread to sleep, and it does not get woken up for > OCELOT_FDMA_CH_SAFE_TIMEOUT_US. During that time, the hardware has done > its thing, but you exit the while loop and return -ETIMEDOUT. > > Fix it by using sane poll API that avoids all problems described above > > Fixes: 753a026cfec1 ("net: ocelot: add FDMA support") > Suggested-by: Andrew Lunn <andrew@lunn.ch> > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> > --- > > Changes since v2: > - Use _atomic variant of readx_poll_timeout > > Changes since v1: > - Fixed typos in title and commit message > - Remove while loop and use readx_poll_timeout as suggested by > Andrew > > --- > drivers/net/ethernet/mscc/ocelot_fdma.c | 17 ++++++++--------- > 1 file changed, 8 insertions(+), 9 deletions(-) > > diff --git a/drivers/net/ethernet/mscc/ocelot_fdma.c b/drivers/net/ethernet/mscc/ocelot_fdma.c > index 083fddd263ec..c93fba0a2a7d 100644 > --- a/drivers/net/ethernet/mscc/ocelot_fdma.c > +++ b/drivers/net/ethernet/mscc/ocelot_fdma.c > @@ -94,19 +94,18 @@ static void ocelot_fdma_activate_chan(struct ocelot *ocelot, dma_addr_t dma, > ocelot_fdma_writel(ocelot, MSCC_FDMA_CH_ACTIVATE, BIT(chan)); > } > > +static u32 ocelot_fdma_read_ch_safe(struct ocelot *ocelot) > +{ > + return ocelot_fdma_readl(ocelot, MSCC_FDMA_CH_SAFE); > +} > + > static int ocelot_fdma_wait_chan_safe(struct ocelot *ocelot, int chan) > { > - unsigned long timeout; > u32 safe; > > - timeout = jiffies + usecs_to_jiffies(OCELOT_FDMA_CH_SAFE_TIMEOUT_US); > - do { > - safe = ocelot_fdma_readl(ocelot, MSCC_FDMA_CH_SAFE); > - if (safe & BIT(chan)) > - return 0; > - } while (time_after(jiffies, timeout)); > - > - return -ETIMEDOUT; > + return readx_poll_timeout_atomic(ocelot_fdma_read_ch_safe, ocelot, safe, > + safe & BIT(chan), 0, > + OCELOT_FDMA_CH_SAFE_TIMEOUT_US); Can you please indent the arguments to the open bracket? > } > > static void ocelot_fdma_dcb_set_data(struct ocelot_fdma_dcb *dcb, > -- > 2.35.1 >
Hi Vladimir, Vladimir Oltean <vladimir.oltean@nxp.com> says: > Can you please indent the arguments to the open bracket? > Sure thing! I've just sent a v4. Thank you for review Thanks, --Pavel Skripkin
On Wed, Jul 06, 2022 at 04:29:45PM +0300, Pavel Skripkin wrote: > Hi Vladimir, > > Vladimir Oltean <vladimir.oltean@nxp.com> says: > > Can you please indent the arguments to the open bracket? > > > > Sure thing! I've just sent a v4. > > Thank you for review And thank you for the patch!
diff --git a/drivers/net/ethernet/mscc/ocelot_fdma.c b/drivers/net/ethernet/mscc/ocelot_fdma.c index 083fddd263ec..c93fba0a2a7d 100644 --- a/drivers/net/ethernet/mscc/ocelot_fdma.c +++ b/drivers/net/ethernet/mscc/ocelot_fdma.c @@ -94,19 +94,18 @@ static void ocelot_fdma_activate_chan(struct ocelot *ocelot, dma_addr_t dma, ocelot_fdma_writel(ocelot, MSCC_FDMA_CH_ACTIVATE, BIT(chan)); } +static u32 ocelot_fdma_read_ch_safe(struct ocelot *ocelot) +{ + return ocelot_fdma_readl(ocelot, MSCC_FDMA_CH_SAFE); +} + static int ocelot_fdma_wait_chan_safe(struct ocelot *ocelot, int chan) { - unsigned long timeout; u32 safe; - timeout = jiffies + usecs_to_jiffies(OCELOT_FDMA_CH_SAFE_TIMEOUT_US); - do { - safe = ocelot_fdma_readl(ocelot, MSCC_FDMA_CH_SAFE); - if (safe & BIT(chan)) - return 0; - } while (time_after(jiffies, timeout)); - - return -ETIMEDOUT; + return readx_poll_timeout_atomic(ocelot_fdma_read_ch_safe, ocelot, safe, + safe & BIT(chan), 0, + OCELOT_FDMA_CH_SAFE_TIMEOUT_US); } static void ocelot_fdma_dcb_set_data(struct ocelot_fdma_dcb *dcb,
Accidentally noticed, that this driver is the only user of while (time_after(jiffies...)). It looks like typo, because likely this while loop will finish after 1st iteration, because time_after() returns true when 1st argument _is after_ 2nd one. There is one possible problem with this poll loop: the scheduler could put the thread to sleep, and it does not get woken up for OCELOT_FDMA_CH_SAFE_TIMEOUT_US. During that time, the hardware has done its thing, but you exit the while loop and return -ETIMEDOUT. Fix it by using sane poll API that avoids all problems described above Fixes: 753a026cfec1 ("net: ocelot: add FDMA support") Suggested-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- Changes since v2: - Use _atomic variant of readx_poll_timeout Changes since v1: - Fixed typos in title and commit message - Remove while loop and use readx_poll_timeout as suggested by Andrew --- drivers/net/ethernet/mscc/ocelot_fdma.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)