Am 23.07.21 um 09:58 schrieb Michel Dänzer:
From: Michel Dänzer mdaenzer@redhat.com
This makes sure we don't hit the
BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
in dma_buf_release, which could be triggered by user space closing the dma-buf file description while there are outstanding fence callbacks from dma_buf_poll.
I was also wondering the same thing while working on this, but then thought that the poll interface would take care of this.
Cc: stable@vger.kernel.org Signed-off-by: Michel Dänzer mdaenzer@redhat.com
drivers/dma-buf/dma-buf.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 6c520c9bd93c..ec25498a971f 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -65,12 +65,9 @@ static void dma_buf_release(struct dentry *dentry) BUG_ON(dmabuf->vmapping_counter); /*
* Any fences that a dma-buf poll can wait on should be signaled* before releasing dma-buf. This is the responsibility of each* driver that uses the reservation objects.** If you hit this BUG() it means someone dropped their ref to the* dma-buf while still having pending operation to the buffer.
* If you hit this BUG() it could mean:* * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else* * dmabuf->cb_in/out.active are non-0 despite no pending fence callback@@ -196,6 +193,7 @@ static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) { struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
- struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll); unsigned long flags;
spin_lock_irqsave(&dcb->poll->lock, flags); @@ -203,6 +201,8 @@ static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) dcb->active = 0; spin_unlock_irqrestore(&dcb->poll->lock, flags); dma_fence_put(fence);
- /* Paired with get_file in dma_buf_poll */
- fput(dmabuf->file);
Is calling fput() in interrupt context ok? IIRC that could potentially sleep.
Regards, Christian.
} static bool dma_buf_poll_shared(struct dma_resv *resv, @@ -278,6 +278,9 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) spin_unlock_irq(&dmabuf->poll.lock); if (events & EPOLLOUT) {
/* Paired with fput in dma_buf_poll_cb */get_file(dmabuf->file);if (!dma_buf_poll_shared(resv, dcb) && !dma_buf_poll_excl(resv, dcb)) /* No callback queued, wake up any other waiters */@@ -299,6 +302,9 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) spin_unlock_irq(&dmabuf->poll.lock); if (events & EPOLLIN) {
/* Paired with fput in dma_buf_poll_cb */get_file(dmabuf->file);if (!dma_buf_poll_excl(resv, dcb)) /* No callback queued, wake up any other waiters */ dma_buf_poll_cb(NULL, &dcb->cb);