diff options
| author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2013-03-28 00:03:25 +0100 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2013-03-28 16:41:13 +0100 |
| commit | 1d5bfac96f1e1856fbdb3f06679691e5b9c2ba8f (patch) | |
| tree | e0ab711e8c18a05f5e08021e708ff287e20247b0 | |
| parent | 6effa33b73fb0129061ecd8ba3158d984475d35d (diff) | |
drm/i915: fix up _wait_for macro
As Thomas Gleixner spotted, it's rather horrible racy:
- We can miss almost a full tick, so need to compensate by 1 jiffy.
- We need to re-check the condition when having timed-out, since a
the last check could have been before the timeout expired. E.g. when
we've been preempted or a long irq happened.
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Jack Winter <jbh@alchemy.lu>
Cc: Jack Winter <jbh@alchemy.lu>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
| -rw-r--r-- | drivers/gpu/drm/i915/intel_drv.h | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 8720a67395f8..18bba6e25e1e 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -33,12 +33,21 @@ #include <drm/drm_fb_helper.h> #include <drm/drm_dp_helper.h> +/** + * _wait_for - magic (register) wait macro + * + * Does the right thing for modeset paths when run under kdgb or similar atomic + * contexts. Note that it's important that we check the condition again after + * having timed out, since the timeout could be due to preemption or similar and + * we've never had a chance to check the condition before the timeout. + */ #define _wait_for(COND, MS, W) ({ \ - unsigned long timeout__ = jiffies + msecs_to_jiffies(MS); \ + unsigned long timeout__ = jiffies + msecs_to_jiffies(MS) + 1; \ int ret__ = 0; \ while (!(COND)) { \ if (time_after(jiffies, timeout__)) { \ - ret__ = -ETIMEDOUT; \ + if (!(COND)) \ + ret__ = -ETIMEDOUT; \ break; \ } \ if (W && drm_can_sleep()) { \ |