linux-kernel - [RFC 01/17] dma-fence: add might_sleep annotation to

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Date:   Tue, 12 May 2020 10:59:28 +0200
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        linux-rdma@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: [RFC 01/17] dma-fence: add might_sleep annotation to _wait()

But only for non-zero timeout, to avoid false positives.

One question here is whether the might_sleep should be unconditional,
or only for real timeouts. I'm not sure, so went with the more
defensive option. But in the interest of locking down the cross-driver
dma_fence rules we might want to be more aggressive.

Cc: linux-media@...r.kernel.org
Cc: linaro-mm-sig@...ts.linaro.org
Cc: linux-rdma@...r.kernel.org
Cc: amd-gfx@...ts.freedesktop.org
Cc: intel-gfx@...ts.freedesktop.org
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Christian König <christian.koenig@....com>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
---
 drivers/dma-buf/dma-fence.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 052a41e2451c..6802125349fb 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -208,6 +208,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
 	if (WARN_ON(timeout < 0))
 		return -EINVAL;
 
+	if (timeout > 0)
+		might_sleep();
+
 	trace_dma_fence_wait_start(fence);
 	if (fence->ops->wait)
 		ret = fence->ops->wait(fence, intr, timeout);
-- 
2.26.2