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authorMarc-André Lureau <marcandre.lureau@redhat.com>2018-08-31 16:53:13 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2018-10-02 18:47:55 +0200
commit35f7f3fb5c65dcdf8315bbfd40a3c1d015663d77 (patch)
treeee28c68a11a4449e7c8df1799a3b317c767c3546 /util
parent9e6bdef224f700c057462a7d5e9b4a2770e04569 (diff)
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util: use fcntl() for qemu_write_pidfile() locking
Daniel Berrangé suggested to use fcntl() locks rather than lockf(). 'man lockf': On Linux, lockf() is just an interface on top of fcntl(2) locking. Many other systems implement lockf() in this way, but note that POSIX.1 leaves the relationship between lockf() and fcntl(2) locks unspecified. A portable application should probably avoid mixing calls to these interfaces. IOW, if its just a shim around fcntl() on many systems, it is clearer if we just use fcntl() directly, as we then know how fcntl() locks will behave if they're on a network filesystem like NFS. Suggested-by: Daniel P. Berrangé <berrange@redhat.com> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20180831145314.14736-3-marcandre.lureau@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'util')
-rw-r--r--util/oslib-posix.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 0e3ab9d..fbd0dc8 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -95,6 +95,11 @@ bool qemu_write_pidfile(const char *path, Error **errp)
while (1) {
struct stat a, b;
+ struct flock lock = {
+ .l_type = F_WRLCK,
+ .l_whence = SEEK_SET,
+ .l_len = 0,
+ };
fd = qemu_open(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
if (fd == -1) {
@@ -107,7 +112,7 @@ bool qemu_write_pidfile(const char *path, Error **errp)
goto fail_close;
}
- if (lockf(fd, F_TLOCK, 0) < 0) {
+ if (fcntl(fd, F_SETLK, &lock)) {
error_setg_errno(errp, errno, "Cannot lock pid file");
goto fail_close;
}