drm/i915/perf: Do not clear pollin for small user read buffers (6352219c) · Commits · 戴 / test

drivers/gpu/drm/i915/i915_perf.c

+11 −50

Original line number	Diff line number	Diff line
		@@ -2963,49 +2963,6 @@ void i915_oa_init_reg_state(const struct intel_context *ce,
		gen8_update_reg_state_unlocked(ce, stream);
		}

		/**
		* i915_perf_read_locked - &i915_perf_stream_ops->read with error normalisation
		* @stream: An i915 perf stream
		* @file: An i915 perf stream file
		* @buf: destination buffer given by userspace
		* @count: the number of bytes userspace wants to read
		* @ppos: (inout) file seek position (unused)
		*
		* Besides wrapping &i915_perf_stream_ops->read this provides a common place to
		* ensure that if we've successfully copied any data then reporting that takes
		* precedence over any internal error status, so the data isn't lost.
		*
		* For example ret will be -ENOSPC whenever there is more buffered data than
		* can be copied to userspace, but that's only interesting if we weren't able
		* to copy some data because it implies the userspace buffer is too small to
		* receive a single record (and we never split records).
		*
		* Another case with ret == -EFAULT is more of a grey area since it would seem
		* like bad form for userspace to ask us to overrun its buffer, but the user
		* knows best:
		*
		* http://yarchive.net/comp/linux/partial_reads_writes.html
		*
		* Returns: The number of bytes copied or a negative error code on failure.
		*/
		static ssize_t i915_perf_read_locked(struct i915_perf_stream *stream,
		struct file *file,
		char __user *buf,
		size_t count,
		loff_t *ppos)
		{
		/* Note we keep the offset (aka bytes read) separate from any
		* error status so that the final check for whether we return
		* the bytes read with a higher precedence than any error (see
		* comment below) doesn't need to be handled/duplicated in
		* stream->ops->read() implementations.
		*/
		size_t offset = 0;
		int ret = stream->ops->read(stream, buf, count, &offset);

		return offset ?: (ret ?: -EAGAIN);
		}

		/**
		* i915_perf_read - handles read() FOP for i915 perf stream FDs
		* @file: An i915 perf stream file
		@@ -3031,7 +2988,8 @@ static ssize_t i915_perf_read(struct file *file,
		{
		struct i915_perf_stream *stream = file->private_data;
		struct i915_perf *perf = stream->perf;
		ssize_t ret;
		size_t offset = 0;
		int ret;

		/* To ensure it's handled consistently we simply treat all reads of a
		* disabled stream as an error. In particular it might otherwise lead
		@@ -3054,13 +3012,12 @@ static ssize_t i915_perf_read(struct file *file,
		return ret;

		mutex_lock(&perf->lock);
		ret = i915_perf_read_locked(stream, file,
		buf, count, ppos);
		ret = stream->ops->read(stream, buf, count, &offset);
		mutex_unlock(&perf->lock);
		} while (ret == -EAGAIN);
		} while (!offset && !ret);
		} else {
		mutex_lock(&perf->lock);
		ret = i915_perf_read_locked(stream, file, buf, count, ppos);
		ret = stream->ops->read(stream, buf, count, &offset);
		mutex_unlock(&perf->lock);
		}

		@@ -3071,11 +3028,15 @@ static ssize_t i915_perf_read(struct file *file,
		* and read() returning -EAGAIN. Clearing the oa.pollin state here
		* effectively ensures we back off until the next hrtimer callback
		* before reporting another EPOLLIN event.
		* The exception to this is if ops->read() returned -ENOSPC which means
		* that more OA data is available than could fit in the user provided
		* buffer. In this case we want the next poll() call to not block.
		*/
		if (ret >= 0 \|\| ret == -EAGAIN)
		if (ret != -ENOSPC)
		stream->pollin = false;

		return ret;
		/* Possible values for ret are 0, -EFAULT, -ENOSPC, -EIO, ... */
		return offset ?: (ret ?: -EAGAIN);
		}

		static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer)

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