[PATCH] add libsync.h helper

[Chris Wilson]

On Mon, Oct 31, 2016 at 12:43:09PM -0400, Rob Clark wrote:
> From: Rob Clark <robclark at freedesktop.org>
> 
> Rather than cut/pasting these couple ioctl wrappers everywhere, just
> stuff them as static-inline into a header.
> 
> This is probably mostly used from mesa, but some drivers, test apps, etc
> may also want to use it from libdrm.
> 
> v2: handle EINTR, add sync_accumulate() based on #dri-devel discussion,
>     etc
> 
> Signed-off-by: Rob Clark <robclark at freedesktop.org>
> ---
>  Makefile.sources |   1 +
>  libsync.h        | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 146 insertions(+)
>  create mode 100644 libsync.h
> 
> diff --git a/Makefile.sources b/Makefile.sources
> index a57036a..10aa1d0 100644
> --- a/Makefile.sources
> +++ b/Makefile.sources
> @@ -13,6 +13,7 @@ LIBDRM_FILES := \
>  	util_math.h
>  
>  LIBDRM_H_FILES := \
> +	libsync.h \
>  	xf86drm.h \
>  	xf86drmMode.h
>  
> diff --git a/libsync.h b/libsync.h
> new file mode 100644
> index 0000000..2f9aafb
> --- /dev/null
> +++ b/libsync.h
> @@ -0,0 +1,145 @@
> +/*
> + *  sync abstraction
> + *  Copyright 2015-2016 Collabora Ltd.
> + *
> + *  Based on the implementation from the Android Open Source Project,
> + *
> + *  Copyright 2012 Google, Inc
> + *
> + *  Permission is hereby granted, free of charge, to any person obtaining a
> + *  copy of this software and associated documentation files (the "Software"),
> + *  to deal in the Software without restriction, including without limitation
> + *  the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + *  and/or sell copies of the Software, and to permit persons to whom the
> + *  Software is furnished to do so, subject to the following conditions:
> + *
> + *  The above copyright notice and this permission notice shall be included in
> + *  all copies or substantial portions of the Software.
> + *
> + *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + *  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + *  OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + *  ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + *  OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef _LIBSYNC_H
> +#define _LIBSYNC_H
> +
> +#include <assert.h>
> +#include <errno.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <sys/ioctl.h>
> +#include <sys/poll.h>
> +#include <unistd.h>
> +
> +#if defined(__cplusplus)
> +extern "C" {
> +#endif
> +
> +/* duplicated from linux/sync_file.h to avoid build-time dependency
> + * on new headers
> + */
> +struct sync_merge_data {
> +	char	name[32];
> +	int32_t	fd2;
> +	int32_t	fence;
> +	uint32_t	flags;
> +	uint32_t	pad;
> +};
> +#define SYNC_IOC_MAGIC		'>'
> +#define SYNC_IOC_MERGE		_IOWR(SYNC_IOC_MAGIC, 3, struct sync_merge_data)
> +
> +
> +
> +static inline int sync_wait(int fd, int timeout)
> +{
> +	struct pollfd fds = {0};

Would have thought you would have gone with fds = { fd, POLLIN }; :)

> +	int ret;
> +
> +	fds.fd = fd;
> +	fds.events = POLLIN;
> +
> +	do {
> +		ret = poll(&fds, 1, timeout);
> +		if (ret > 0) {
> +			if (fds.revents & (POLLERR | POLLNVAL)) {
> +				errno = EINVAL;
> +				return -1;
> +			}
> +			return 0;
> +		} else if (ret == 0) {
> +			errno = ETIME;
> +			return -1;
> +		}
> +	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
> +
> +	return ret;
> +}
> +
> +static inline int sync_merge(const char *name, int fd1, int fd2)
> +{
> +	struct sync_merge_data data = {0};
> +	int ret;
> +
> +	data.fd2 = fd2;
> +	strncpy(data.name, name, sizeof(data.name));
> +
> +	do {
> +		ret = ioctl(fd1, SYNC_IOC_MERGE, &data);
> +	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	return data.fence;
> +}
> +
> +/* accumulate fd2 into fd1.  If *fd1 is not a valid fd then dup fd2,
> + * otherwise sync_merge() and close the old *fd1.  This can be used
> + * to implement the pattern:
> + *
> + *    init()
> + *    {
> + *       batch.fence_fd = 1;

-1

> + *    }
> + *
> + *    // does *NOT* take ownership of fd
> + *    server_sync(int fd)
> + *    {
> + *       if (sync_accumulate("foo", &batch.fence_fd, fd)) {
> + *          ... error ...
> + *       }
> + *    }
> + */
> +static inline int sync_accumulate(const char *name, int *fd1, int fd2)
> +{
> +	int ret;
> +
> +	assert(fd2 >= 0);
> +
> +	if (*fd1 < 0) {
> +		*fd1 = dup(fd2);
> +		return 0;
> +	}
> +
> +	ret = sync_merge(name, *fd1, fd2);
> +	if (ret < 0) {
> +		/* leave *fd1 as it is */
> +		return ret;
> +	}
> +
> +	close(*fd1);
> +	*fd1 = ret;
> +
> +	return 0;
> +}

Lgtm, matches how we want to use it.
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre