From d538bbdfde34028b5c5b0ba92b3c2096c5afb82c Mon Sep 17 00:00:00 2001 From: Damien Lespiau Date: Mon, 21 Oct 2013 14:29:30 +0100 Subject: drm/i915: Use a spin lock to protect the pipe crc struct Daniel pointed out that it was hard to get anything lockless to work correctly, so don't even try for this non critical piece of code and just use a spin lock. v2: Make intel_pipe_crc->opened a bool v3: Use assert_spin_locked() instead of a comment (Daniel Vetter) v4: Use spin_lock_irq() in the debugfs functions (they can only be called from process context), Use spin_lock() in the pipe_crc_update() function that can only be called from an interrupt handler, Use wait_event_interruptible_lock_irq() when waiting for data in the cicular buffer to ensure proper locking around the condition we are waiting for. (Daniel Vetter) Suggested-by: Daniel Vetter Signed-off-by: Damien Lespiau Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_irq.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'drivers/gpu/drm/i915/i915_irq.c') diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 8f7baad72316..1a7dc7754e2f 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -1200,15 +1200,19 @@ static void display_pipe_crc_irq_handler(struct drm_device *dev, enum pipe pipe, struct intel_pipe_crc_entry *entry; int head, tail; + spin_lock(&pipe_crc->lock); + if (!pipe_crc->entries) { + spin_unlock(&pipe_crc->lock); DRM_ERROR("spurious interrupt\n"); return; } - head = atomic_read(&pipe_crc->head); - tail = atomic_read(&pipe_crc->tail); + head = pipe_crc->head; + tail = pipe_crc->tail; if (CIRC_SPACE(head, tail, INTEL_PIPE_CRC_ENTRIES_NR) < 1) { + spin_unlock(&pipe_crc->lock); DRM_ERROR("CRC buffer overflowing\n"); return; } @@ -1223,7 +1227,9 @@ static void display_pipe_crc_irq_handler(struct drm_device *dev, enum pipe pipe, entry->crc[4] = crc4; head = (head + 1) & (INTEL_PIPE_CRC_ENTRIES_NR - 1); - atomic_set(&pipe_crc->head, head); + pipe_crc->head = head; + + spin_unlock(&pipe_crc->lock); wake_up_interruptible(&pipe_crc->wq); } -- cgit v1.2.2