From: Daniel Vetter <daniel@ffwll.ch>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked
Date: Tue, 7 Apr 2015 16:04:22 +0200 [thread overview]
Message-ID: <20150407140422.GJ6354@phenom.ffwll.local> (raw)
In-Reply-To: <5523E0F0.10403@linux.intel.com>
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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prev parent reply other threads:[~2015-04-07 14:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
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