149 lines
3.4 KiB
C
149 lines
3.4 KiB
C
/*
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* sync abstraction
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* Copyright 2015-2016 Collabora Ltd.
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*
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* Based on the implementation from the Android Open Source Project,
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*
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* Copyright 2012 Google, Inc
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef _LIBSYNC_H
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#define _LIBSYNC_H
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#include <assert.h>
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#include <errno.h>
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#include <stdint.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include <sys/poll.h>
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#include <unistd.h>
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#if defined(__cplusplus)
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extern "C" {
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#endif
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#ifndef SYNC_IOC_MERGE
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/* duplicated from linux/sync_file.h to avoid build-time dependency
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* on new (v4.7) kernel headers. Once distro's are mostly using
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* something newer than v4.7 drop this and #include <linux/sync_file.h>
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* instead.
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*/
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struct sync_merge_data {
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char name[32];
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int32_t fd2;
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int32_t fence;
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uint32_t flags;
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uint32_t pad;
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};
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#define SYNC_IOC_MAGIC '>'
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#define SYNC_IOC_MERGE _IOWR(SYNC_IOC_MAGIC, 3, struct sync_merge_data)
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#endif
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static inline int sync_wait(int fd, int timeout)
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{
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struct pollfd fds = {0};
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int ret;
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fds.fd = fd;
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fds.events = POLLIN;
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do {
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ret = poll(&fds, 1, timeout);
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if (ret > 0) {
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if (fds.revents & (POLLERR | POLLNVAL)) {
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errno = EINVAL;
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return -1;
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}
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return 0;
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} else if (ret == 0) {
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errno = ETIME;
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return -1;
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}
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} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
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return ret;
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}
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static inline int sync_merge(const char *name, int fd1, int fd2)
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{
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struct sync_merge_data data = {0};
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int ret;
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data.fd2 = fd2;
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strncpy(data.name, name, sizeof(data.name));
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do {
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ret = ioctl(fd1, SYNC_IOC_MERGE, &data);
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} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
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if (ret < 0)
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return ret;
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return data.fence;
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}
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/* accumulate fd2 into fd1. If *fd1 is not a valid fd then dup fd2,
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* otherwise sync_merge() and close the old *fd1. This can be used
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* to implement the pattern:
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*
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* init()
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* {
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* batch.fence_fd = -1;
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* }
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*
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* // does *NOT* take ownership of fd
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* server_sync(int fd)
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* {
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* if (sync_accumulate("foo", &batch.fence_fd, fd)) {
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* ... error ...
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* }
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* }
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*/
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static inline int sync_accumulate(const char *name, int *fd1, int fd2)
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{
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int ret;
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assert(fd2 >= 0);
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if (*fd1 < 0) {
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*fd1 = dup(fd2);
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return 0;
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}
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ret = sync_merge(name, *fd1, fd2);
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if (ret < 0) {
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/* leave *fd1 as it is */
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return ret;
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}
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close(*fd1);
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*fd1 = ret;
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return 0;
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}
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#if defined(__cplusplus)
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}
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#endif
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#endif
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