d284b82b3e
This doesn't have much effect on the final build, because we link libbasic.a
into libsystemd-shared.so, so in the end, all the object built from basic/
end up in libsystemd-shared. And when the static library is linked into binaries,
any objects that are included in it but are not used are trimmed. Hence, the
size of output artifacts doesn't change:
$ du -sb /var/tmp/inst*
54181861 /var/tmp/inst1 (old)
54207441 /var/tmp/inst1s (old split-usr)
54182477 /var/tmp/inst2 (new)
54208041 /var/tmp/inst2s (new split-usr)
(The negligible change in size is because libsystemd-shared.so is bigger
by a few hundred bytes. I guess it's because symbols are named differently
or something like that.)
The effect is on the build process, in particular partial builds. This change
effectively moves the requirements on some build steps toward the leaves of the
dependency tree. Two effects:
- when building items that do not depend on libsystemd-shared, we
build less stuff for libbasic.a (which wouldn't be used anyway,
so it's a net win).
- when building items that do depend on libshared, we reduce libbasic.a as a
synchronization point, possibly allowing better parallelism.
Method:
1. copy list of .h files from src/basic/meson.build to /tmp/basic
2. $ for i in $(grep '.h$' /tmp/basic); do echo $i; git --no-pager grep "include \"$i\"" src/basic/ 'src/lib*' 'src/nss-*' 'src/journal/sd-journal.c' |grep -v "${i%.h}.c";echo ;done | less
137 lines
4 KiB
C
137 lines
4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/file.h>
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#include <sys/stat.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "fs-util.h"
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#include "lockfile-util.h"
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#include "macro.h"
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#include "path-util.h"
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int make_lock_file(const char *p, int operation, LockFile *ret) {
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_cleanup_close_ int fd = -1;
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_cleanup_free_ char *t = NULL;
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int r;
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/*
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* We use UNPOSIX locks if they are available. They have nice
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* semantics, and are mostly compatible with NFS. However,
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* they are only available on new kernels. When we detect we
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* are running on an older kernel, then we fall back to good
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* old BSD locks. They also have nice semantics, but are
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* slightly problematic on NFS, where they are upgraded to
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* POSIX locks, even though locally they are orthogonal to
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* POSIX locks.
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*/
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t = strdup(p);
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if (!t)
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return -ENOMEM;
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for (;;) {
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struct flock fl = {
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.l_type = (operation & ~LOCK_NB) == LOCK_EX ? F_WRLCK : F_RDLCK,
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.l_whence = SEEK_SET,
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};
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struct stat st;
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fd = open(p, O_CREAT|O_RDWR|O_NOFOLLOW|O_CLOEXEC|O_NOCTTY, 0600);
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if (fd < 0)
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return -errno;
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r = fcntl(fd, (operation & LOCK_NB) ? F_OFD_SETLK : F_OFD_SETLKW, &fl);
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if (r < 0) {
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/* If the kernel is too old, use good old BSD locks */
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if (errno == EINVAL)
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r = flock(fd, operation);
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if (r < 0)
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return errno == EAGAIN ? -EBUSY : -errno;
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}
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/* If we acquired the lock, let's check if the file
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* still exists in the file system. If not, then the
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* previous exclusive owner removed it and then closed
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* it. In such a case our acquired lock is worthless,
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* hence try again. */
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r = fstat(fd, &st);
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if (r < 0)
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return -errno;
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if (st.st_nlink > 0)
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break;
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fd = safe_close(fd);
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}
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ret->path = t;
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ret->fd = fd;
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ret->operation = operation;
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fd = -1;
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t = NULL;
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return r;
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}
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int make_lock_file_for(const char *p, int operation, LockFile *ret) {
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const char *fn;
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char *t;
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assert(p);
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assert(ret);
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fn = basename(p);
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if (!filename_is_valid(fn))
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return -EINVAL;
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t = newa(char, strlen(p) + 2 + 4 + 1);
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stpcpy(stpcpy(stpcpy(mempcpy(t, p, fn - p), ".#"), fn), ".lck");
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return make_lock_file(t, operation, ret);
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}
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void release_lock_file(LockFile *f) {
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int r;
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if (!f)
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return;
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if (f->path) {
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/* If we are the exclusive owner we can safely delete
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* the lock file itself. If we are not the exclusive
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* owner, we can try becoming it. */
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if (f->fd >= 0 &&
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(f->operation & ~LOCK_NB) == LOCK_SH) {
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static const struct flock fl = {
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.l_type = F_WRLCK,
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.l_whence = SEEK_SET,
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};
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r = fcntl(f->fd, F_OFD_SETLK, &fl);
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if (r < 0 && errno == EINVAL)
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r = flock(f->fd, LOCK_EX|LOCK_NB);
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if (r >= 0)
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f->operation = LOCK_EX|LOCK_NB;
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}
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if ((f->operation & ~LOCK_NB) == LOCK_EX)
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unlink_noerrno(f->path);
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f->path = mfree(f->path);
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}
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f->fd = safe_close(f->fd);
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f->operation = 0;
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}
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