Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > Quoting Mika Kuoppala (2017-07-19 12:18:47) >> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: >> >> > Workers on the i915->wq may rearm themselves so for completeness we need >> > to replace our flush_workqueue() with a call to drain_workqueue() before >> > unloading the device. >> > >> > v2: Reinforce the drain_workqueue with an preceeding rcu_barrier() as a >> > few of the tasks that need to be drained may first be armed by RCU. >> > >> > References: https://bugs.freedesktop.org/show_bug.cgi?id=101627 >> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> >> > Cc: Matthew Auld <matthew.auld@xxxxxxxxx> >> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> >> > --- >> > drivers/gpu/drm/i915/i915_drv.c | 6 ++---- >> > drivers/gpu/drm/i915/i915_drv.h | 20 ++++++++++++++++++++ >> > drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 +- >> > 3 files changed, 23 insertions(+), 5 deletions(-) >> > >> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c >> > index 4b62fd012877..41c5b11a7c8f 100644 >> > --- a/drivers/gpu/drm/i915/i915_drv.c >> > +++ b/drivers/gpu/drm/i915/i915_drv.c >> > @@ -596,7 +596,8 @@ static const struct vga_switcheroo_client_ops i915_switcheroo_ops = { >> > >> > static void i915_gem_fini(struct drm_i915_private *dev_priv) >> > { >> > - flush_workqueue(dev_priv->wq); >> > + /* Flush any outstanding unpin_work. */ >> > + i915_gem_drain_workqueue(dev_priv); >> > >> > mutex_lock(&dev_priv->drm.struct_mutex); >> > intel_uc_fini_hw(dev_priv); >> > @@ -1409,9 +1410,6 @@ void i915_driver_unload(struct drm_device *dev) >> > cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work); >> > i915_reset_error_state(dev_priv); >> > >> > - /* Flush any outstanding unpin_work. */ >> > - drain_workqueue(dev_priv->wq); >> > - >> > i915_gem_fini(dev_priv); >> > intel_uc_fini_fw(dev_priv); >> > intel_fbc_cleanup_cfb(dev_priv); >> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h >> > index 667fb5c44483..e9a4b96dc775 100644 >> > --- a/drivers/gpu/drm/i915/i915_drv.h >> > +++ b/drivers/gpu/drm/i915/i915_drv.h >> > @@ -3300,6 +3300,26 @@ static inline void i915_gem_drain_freed_objects(struct drm_i915_private *i915) >> > } while (flush_work(&i915->mm.free_work)); >> > } >> > >> > +static inline void i915_gem_drain_workqueue(struct drm_i915_private *i915) >> > +{ >> > + /* >> > + * Similar to objects above (see i915_gem_drain_freed-objects), in >> > + * general we have workers that are armed by RCU and then rearm >> > + * themselves in their callbacks. To be paranoid, we need to >> > + * drain the workqueue a second time after waiting for the RCU >> > + * grace period so that we catch work queued via RCU from the first >> > + * pass. As neither drain_workqueue() nor flush_workqueue() report >> > + * a result, we make an assumption that we only don't require more >> > + * than 2 passes to catch all recursive RCU delayed work. >> > + * >> > + */ >> > + int pass = 2; >> > + do { >> > + rcu_barrier(); >> > + drain_workqueue(i915->wq); >> >> I am fine with the paranoia, and it covers the case below. Still if we do: >> >> drain_workqueue(); >> rcu_barrier(); >> >> With drawining in progress, only chain queuing is allowed. I understand >> this so that when it returns, all the ctx pointers are now unreferenced >> but not freed. >> >> Thus the rcu_barrier() after it cleans the trash and we are good to >> be unloaded. With one pass. >> >> I guess it comes to how to understand the comment, so could you >> elaborate the 'we have workers that are armed by RCU and then rearm >> themselves'?. As from drain_workqueue desc, this should be covered. > > I'm considering that they may be rearmed via RCU in the general case, > e.g. context close frees an object and so goes onto an RCU list that > once processed kicks off a new worker and so requires another round of > drain_workqueue. We are in module unload so a few extra delays to belts > and braces are ok until somebody notices it takes a few minutes to run a > reload test ;) Ok. Patch is Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> > -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
