/*
* 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
#ifndef SYNC_IOC_MERGE
/* duplicated from linux/sync_file.h to avoid build-time dependency
* on new (v4.7) kernel headers. Once distro's are mostly using
* something newer than v4.7 drop this and #include <linux/sync_file.h>
* instead.
*/
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)
#endif
static inline int sync_wait(int fd, int timeout)
{
struct pollfd fds = {0};
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;
* }
*
* // 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;
}
#if defined(__cplusplus)
}
#endif
#endif