* [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked
@ 2015-04-07 9:32 Maarten Lankhorst
2015-04-07 13:37 ` Daniel Vetter
0 siblings, 1 reply; 4+ messages in thread
From: Maarten Lankhorst @ 2015-04-07 9:32 UTC (permalink / raw)
To: Intel Graphics Development
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b13c5526a73b..7aaf8eddf19c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2146,14 +2146,14 @@ i915_gem_request_unreference(struct drm_i915_gem_request *req)
static inline void
i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
{
- if (req && !atomic_add_unless(&req->ref.refcount, -1, 1)) {
- struct drm_device *dev = req->ring->dev;
+ struct drm_device *dev;
+
+ if (!req)
+ return;
- mutex_lock(&dev->struct_mutex);
- if (likely(atomic_dec_and_test(&req->ref.refcount)))
- i915_gem_request_free(&req->ref);
+ dev = req->ring->dev;
+ if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
mutex_unlock(&dev->struct_mutex);
- }
}
static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst,
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^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked
2015-04-07 9:32 [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked Maarten Lankhorst
@ 2015-04-07 13:37 ` Daniel Vetter
2015-04-07 13:51 ` Maarten Lankhorst
0 siblings, 1 reply; 4+ messages in thread
From: Daniel Vetter @ 2015-04-07 13:37 UTC (permalink / raw)
To: Maarten Lankhorst; +Cc: Intel Graphics Development
On Tue, Apr 07, 2015 at 11:32:02AM +0200, Maarten Lankhorst wrote:
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index b13c5526a73b..7aaf8eddf19c 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2146,14 +2146,14 @@ i915_gem_request_unreference(struct drm_i915_gem_request *req)
> static inline void
> i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
> {
> - if (req && !atomic_add_unless(&req->ref.refcount, -1, 1)) {
> - struct drm_device *dev = req->ring->dev;
> + struct drm_device *dev;
> +
> + if (!req)
> + return;
>
> - mutex_lock(&dev->struct_mutex);
> - if (likely(atomic_dec_and_test(&req->ref.refcount)))
> - i915_gem_request_free(&req->ref);
> + dev = req->ring->dev;
> + if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
> mutex_unlock(&dev->struct_mutex);
We don't need this conditional unlock here since that's only possible if
you have a weak reference somewhere (i.e. using kref_get_unless_zero). If
the object only has strong references and you're dropping the last one it
can't magically get resurrected somehow.
And drm_gem_object_unreference_unlocked wants the same patch I think.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked
2015-04-07 13:37 ` Daniel Vetter
@ 2015-04-07 13:51 ` Maarten Lankhorst
2015-04-07 14:04 ` Daniel Vetter
0 siblings, 1 reply; 4+ messages in thread
From: Maarten Lankhorst @ 2015-04-07 13:51 UTC (permalink / raw)
To: Daniel Vetter; +Cc: Intel Graphics Development
Op 07-04-15 om 15:37 schreef Daniel Vetter:
> On Tue, Apr 07, 2015 at 11:32:02AM +0200, Maarten Lankhorst wrote:
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> ---
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index b13c5526a73b..7aaf8eddf19c 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -2146,14 +2146,14 @@ i915_gem_request_unreference(struct drm_i915_gem_request *req)
>> static inline void
>> i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
>> {
>> - if (req && !atomic_add_unless(&req->ref.refcount, -1, 1)) {
>> - struct drm_device *dev = req->ring->dev;
>> + struct drm_device *dev;
>> +
>> + if (!req)
>> + return;
>>
>> - mutex_lock(&dev->struct_mutex);
>> - if (likely(atomic_dec_and_test(&req->ref.refcount)))
>> - i915_gem_request_free(&req->ref);
>> + dev = req->ring->dev;
>> + if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
>> mutex_unlock(&dev->struct_mutex);
> We don't need this conditional unlock here since that's only possible if
> you have a weak reference somewhere (i.e. using kref_get_unless_zero). If
> the object only has strong references and you're dropping the last one it
> can't magically get resurrected somehow.
Because we use the same put call for kref_put and kref_put_mutex we do need to unlock struct_mutex here,
kref_put_mutex doesn't release the mutex if true, so either the release call needs to do it or the callee.
> And drm_gem_object_unreference_unlocked wants the same patch I think.
Indeed it does, but with slightly more lockdep annotation!
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked
2015-04-07 13:51 ` Maarten Lankhorst
@ 2015-04-07 14:04 ` Daniel Vetter
0 siblings, 0 replies; 4+ messages in thread
From: Daniel Vetter @ 2015-04-07 14:04 UTC (permalink / raw)
To: Maarten Lankhorst; +Cc: Intel Graphics Development
On Tue, Apr 07, 2015 at 03:51:44PM +0200, Maarten Lankhorst wrote:
> Op 07-04-15 om 15:37 schreef Daniel Vetter:
> > On Tue, Apr 07, 2015 at 11:32:02AM +0200, Maarten Lankhorst wrote:
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >> ---
> >> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> >> index b13c5526a73b..7aaf8eddf19c 100644
> >> --- a/drivers/gpu/drm/i915/i915_drv.h
> >> +++ b/drivers/gpu/drm/i915/i915_drv.h
> >> @@ -2146,14 +2146,14 @@ i915_gem_request_unreference(struct drm_i915_gem_request *req)
> >> static inline void
> >> i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
> >> {
> >> - if (req && !atomic_add_unless(&req->ref.refcount, -1, 1)) {
> >> - struct drm_device *dev = req->ring->dev;
> >> + struct drm_device *dev;
> >> +
> >> + if (!req)
> >> + return;
> >>
> >> - mutex_lock(&dev->struct_mutex);
> >> - if (likely(atomic_dec_and_test(&req->ref.refcount)))
> >> - i915_gem_request_free(&req->ref);
> >> + dev = req->ring->dev;
> >> + if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
> >> mutex_unlock(&dev->struct_mutex);
> > We don't need this conditional unlock here since that's only possible if
> > you have a weak reference somewhere (i.e. using kref_get_unless_zero). If
> > the object only has strong references and you're dropping the last one it
> > can't magically get resurrected somehow.
> Because we use the same put call for kref_put and kref_put_mutex we do need to unlock struct_mutex here,
> kref_put_mutex doesn't release the mutex if true, so either the release call needs to do it or the callee.
Indeed I didn't realize that all existing users of kref_put_mutex unlock
the mutex in the free callback. So looks all good, so applied it.
Thanks, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-04-07 9:32 [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked Maarten Lankhorst
2015-04-07 13:37 ` Daniel Vetter
2015-04-07 13:51 ` Maarten Lankhorst
2015-04-07 14:04 ` Daniel Vetter
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