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reservation: add suppport for read-only access using rcu

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This adds some extra functions to deal with rcu.

reservation_object_get_fences_rcu() will obtain the list of shared
and exclusive fences without obtaining the ww_mutex.

reservation_object_wait_timeout_rcu() will wait on all fences of the
reservation_object, without obtaining the ww_mutex.

reservation_object_test_signaled_rcu() will test if all fences of the
reservation_object are signaled without using the ww_mutex.

reservation_object_get_excl and reservation_object_get_list require
the reservation object to be held, updating requires
write_seqcount_begin/end. If only the exclusive fence is needed,
rcu_dereference followed by fence_get_rcu can be used, if the shared
fences are needed it's recommended to use the supplied functions.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Reviewed-By: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maarten Lankhorst
2014-07-01 12:58:00 +02:00
committed by Greg Kroah-Hartman
parent 04a5faa8cb
commit 3c3b177a93
5 changed files with 400 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/dma-buf/dma-buf.c
+36 -11
View File
@@ -137,7 +137,7 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
struct reservation_object_list *fobj;
struct fence *fence_excl;
unsigned long events;
unsigned shared_count;
unsigned shared_count, seq;
dmabuf = file->private_data;
if (!dmabuf || !dmabuf->resv)
@@ -151,14 +151,20 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
if (!events)
return 0;
ww_mutex_lock(&resv->lock, NULL);
retry:
seq = read_seqcount_begin(&resv->seq);
rcu_read_lock();
fobj = resv->fence;
if (!fobj)
goto out;
shared_count = fobj->shared_count;
fence_excl = resv->fence_excl;
fobj = rcu_dereference(resv->fence);
if (fobj)
shared_count = fobj->shared_count;
else
shared_count = 0;
fence_excl = rcu_dereference(resv->fence_excl);
if (read_seqcount_retry(&resv->seq, seq)) {
rcu_read_unlock();
goto retry;
}
if (fence_excl && (!(events & POLLOUT) || shared_count == 0)) {
struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
@@ -176,14 +182,20 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
spin_unlock_irq(&dmabuf->poll.lock);
if (events & pevents) {
if (!fence_add_callback(fence_excl, &dcb->cb,
if (!fence_get_rcu(fence_excl)) {
/* force a recheck */
events &= ~pevents;
dma_buf_poll_cb(NULL, &dcb->cb);
} else if (!fence_add_callback(fence_excl, &dcb->cb,
dma_buf_poll_cb)) {
events &= ~pevents;
fence_put(fence_excl);
} else {
/*
* No callback queued, wake up any additional
* waiters.
*/
fence_put(fence_excl);
dma_buf_poll_cb(NULL, &dcb->cb);
}
}
@@ -205,13 +217,26 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
goto out;
for (i = 0; i < shared_count; ++i) {
struct fence *fence = fobj->shared[i];
struct fence *fence = rcu_dereference(fobj->shared[i]);
if (!fence_get_rcu(fence)) {
/*
* fence refcount dropped to zero, this means
* that fobj has been freed
*
* call dma_buf_poll_cb and force a recheck!
*/
events &= ~POLLOUT;
dma_buf_poll_cb(NULL, &dcb->cb);
break;
}
if (!fence_add_callback(fence, &dcb->cb,
dma_buf_poll_cb)) {
fence_put(fence);
events &= ~POLLOUT;
break;
}
fence_put(fence);
}
/* No callback queued, wake up any additional waiters. */
@@ -220,7 +245,7 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
}
out:
ww_mutex_unlock(&resv->lock);
rcu_read_unlock();
return events;
}