| Message ID | 1484478758-13133-1-git-send-email-hofrat@osadl.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Sun, Jan 15, 2017 at 12:12:38PM +0100, Nicholas Mc Guire wrote: > Using counter based retry loops for peripherals results in the delay > being significantly overrun during high-load situations where delay > functions tend to be vary imprecise and overrun there timeouts. So > condition the termination on the actual condition of 2s for the > re-calibration to have been successful. > > As this is a very long delay there is no advantage in using > high-resolution timers thus switching this to msleep(). > > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org> Applied, thank you. > --- > > V2: The maximum recalibration timeout should have been 2 * HZ as > Dmitry Torokhov <dmitry.torokhov@gmail.com> noted - V2 sets > the timeout boundary to 2s now. > > Problem detected with coccinelle script (usleep_range for long delay) > > The basic model for the fix up here is to use > > timeout = jiffies + (retry_time) > do { > check() > mleep() > } while (time_is_after_jiffies(timeout)); > > rather than using a counter and have very long retry loops under load > conditions. In the specific case it is sleep()/check() though to wait > on the previous write to complete. The initial intent was to move the > usleep_range() to msleep() as the delays are very long - if this > refactoring of the timeout loop is desirable or not is not clear (both > time and count based models seem to be common). > > Patch was compile tested with: x86_64_defconfig + CONFIG_MOUSE_CYAPA=m > > Patch is against 4.10-rc3 (localversion-next is next-20170113) > > drivers/input/mouse/cyapa_gen3.c | 27 ++++++++++++--------------- > 1 file changed, 12 insertions(+), 15 deletions(-) > > diff --git a/drivers/input/mouse/cyapa_gen3.c b/drivers/input/mouse/cyapa_gen3.c > index f9600753..0c544de 100644 > --- a/drivers/input/mouse/cyapa_gen3.c > +++ b/drivers/input/mouse/cyapa_gen3.c > @@ -789,7 +789,7 @@ static ssize_t cyapa_gen3_do_calibrate(struct device *dev, > const char *buf, size_t count) > { > struct cyapa *cyapa = dev_get_drvdata(dev); > - int tries; > + unsigned long timeout; > int ret; > > ret = cyapa_read_byte(cyapa, CYAPA_CMD_DEV_STATUS); > @@ -812,31 +812,28 @@ static ssize_t cyapa_gen3_do_calibrate(struct device *dev, > goto out; > } > > - tries = 20; /* max recalibration timeout 2s. */ > + /* max recalibration timeout 2s. */ > + timeout = jiffies + 2 * HZ; > do { > /* > * For this recalibration, the max time will not exceed 2s. > * The average time is approximately 500 - 700 ms, and we > * will check the status every 100 - 200ms. > */ > - usleep_range(100000, 200000); > - > + msleep(100); > ret = cyapa_read_byte(cyapa, CYAPA_CMD_DEV_STATUS); > if (ret < 0) { > - dev_err(dev, "Error reading dev status: %d\n", > - ret); > + dev_err(dev, "Error reading dev status: %d\n", ret); > goto out; > } > - if ((ret & CYAPA_DEV_NORMAL) == CYAPA_DEV_NORMAL) > - break; > - } while (--tries); > + if ((ret & CYAPA_DEV_NORMAL) == CYAPA_DEV_NORMAL) { > + dev_dbg(dev, "Calibration successful.\n"); > + goto out; > + } > + } while (time_is_after_jiffies(timeout)); > > - if (tries == 0) { > - dev_err(dev, "Failed to calibrate. Timeout.\n"); > - ret = -ETIMEDOUT; > - goto out; > - } > - dev_dbg(dev, "Calibration successful.\n"); > + dev_err(dev, "Failed to calibrate. Timeout.\n"); > + ret = -ETIMEDOUT; > > out: > return ret < 0 ? ret : count; > -- > 2.1.4 >
diff --git a/drivers/input/mouse/cyapa_gen3.c b/drivers/input/mouse/cyapa_gen3.c index f9600753..0c544de 100644 --- a/drivers/input/mouse/cyapa_gen3.c +++ b/drivers/input/mouse/cyapa_gen3.c @@ -789,7 +789,7 @@ static ssize_t cyapa_gen3_do_calibrate(struct device *dev, const char *buf, size_t count) { struct cyapa *cyapa = dev_get_drvdata(dev); - int tries; + unsigned long timeout; int ret; ret = cyapa_read_byte(cyapa, CYAPA_CMD_DEV_STATUS); @@ -812,31 +812,28 @@ static ssize_t cyapa_gen3_do_calibrate(struct device *dev, goto out; } - tries = 20; /* max recalibration timeout 2s. */ + /* max recalibration timeout 2s. */ + timeout = jiffies + 2 * HZ; do { /* * For this recalibration, the max time will not exceed 2s. * The average time is approximately 500 - 700 ms, and we * will check the status every 100 - 200ms. */ - usleep_range(100000, 200000); - + msleep(100); ret = cyapa_read_byte(cyapa, CYAPA_CMD_DEV_STATUS); if (ret < 0) { - dev_err(dev, "Error reading dev status: %d\n", - ret); + dev_err(dev, "Error reading dev status: %d\n", ret); goto out; } - if ((ret & CYAPA_DEV_NORMAL) == CYAPA_DEV_NORMAL) - break; - } while (--tries); + if ((ret & CYAPA_DEV_NORMAL) == CYAPA_DEV_NORMAL) { + dev_dbg(dev, "Calibration successful.\n"); + goto out; + } + } while (time_is_after_jiffies(timeout)); - if (tries == 0) { - dev_err(dev, "Failed to calibrate. Timeout.\n"); - ret = -ETIMEDOUT; - goto out; - } - dev_dbg(dev, "Calibration successful.\n"); + dev_err(dev, "Failed to calibrate. Timeout.\n"); + ret = -ETIMEDOUT; out: return ret < 0 ? ret : count;
Using counter based retry loops for peripherals results in the delay being significantly overrun during high-load situations where delay functions tend to be vary imprecise and overrun there timeouts. So condition the termination on the actual condition of 2s for the re-calibration to have been successful. As this is a very long delay there is no advantage in using high-resolution timers thus switching this to msleep(). Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org> --- V2: The maximum recalibration timeout should have been 2 * HZ as Dmitry Torokhov <dmitry.torokhov@gmail.com> noted - V2 sets the timeout boundary to 2s now. Problem detected with coccinelle script (usleep_range for long delay) The basic model for the fix up here is to use timeout = jiffies + (retry_time) do { check() mleep() } while (time_is_after_jiffies(timeout)); rather than using a counter and have very long retry loops under load conditions. In the specific case it is sleep()/check() though to wait on the previous write to complete. The initial intent was to move the usleep_range() to msleep() as the delays are very long - if this refactoring of the timeout loop is desirable or not is not clear (both time and count based models seem to be common). Patch was compile tested with: x86_64_defconfig + CONFIG_MOUSE_CYAPA=m Patch is against 4.10-rc3 (localversion-next is next-20170113) drivers/input/mouse/cyapa_gen3.c | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-)