That's the way it should've been all the time. It was originally the case, but then the rework to virFileFlock() made the function ambiguous when it was created in commit 5a0a5f7fb5f5, and due to that it was misused in commit 657ddeff2313 and since then the lock being taken was shared rather than exclusive. Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; --- src/util/virresctrl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/util/virresctrl.c b/src/util/virresctrl.c index 3563fc560db5..9b78a6cb159b 100644 --- a/src/util/virresctrl.c +++ b/src/util/virresctrl.c @@ -463,7 +463,7 @@ virResctrlLockWrite(void) return -1; } - if (virFileFlock(fd, true, true) < 0) { + if (virFileFlock(fd, true, false) < 0) { virReportSystemError(errno, "%s", _("Cannot lock resctrl")); VIR_FORCE_CLOSE(fd); return -1; -- 2.28.0

It was created to get rid of conditional compilation in the resctrl code and make it usable anywhere else. However this is not something that is going to be used in other places because it is not portable and resctrl is just very specific in this regard. And there is no reason why there could not be a preprocessor conditional in the resctrl code. Also the interface of virFileFlock() was very ambiguous which lead to some issues. Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; --- src/libvirt_private.syms | 1 - src/util/virfile.c | 31 +------------------------------ src/util/virfile.h | 2 -- src/util/virresctrl.c | 17 +++++++++++++++-- 4 files changed, 16 insertions(+), 35 deletions(-) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index eea31a736def..fbbe07becbcf 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -2074,7 +2074,6 @@ virFileFindHugeTLBFS; virFileFindMountPoint; virFileFindResource; virFileFindResourceFull; -virFileFlock; virFileFreeACLs; virFileGetACLs; virFileGetDefaultHugepage; diff --git a/src/util/virfile.c b/src/util/virfile.c index af150421e726..b1ca3adcff04 100644 --- a/src/util/virfile.c +++ b/src/util/virfile.c @@ -463,30 +463,9 @@ int virFileUnlock(int fd, off_t start, off_t len) } -/** - * virFileFlock: - * @fd: file descriptor to call flock on - * @lock: true for lock, false for unlock - * @shared: true if shared, false for exclusive, ignored if `@lock == false` - * - * This is just a simple wrapper around flock(2) that errors out on unsupported - * platforms. - * - * The lock will be released when @fd is closed or this function is called with - * `@lock == false`. - * - * Returns 0 on success, -1 otherwise (with errno set) - */ -int virFileFlock(int fd, bool lock, bool shared) -{ - if (lock) - return flock(fd, shared ? LOCK_SH : LOCK_EX); - - return flock(fd, LOCK_UN); -} - #else /* WIN32 */ + int virFileLock(int fd G_GNUC_UNUSED, bool shared G_GNUC_UNUSED, off_t start G_GNUC_UNUSED, @@ -505,14 +484,6 @@ int virFileUnlock(int fd G_GNUC_UNUSED, } -int virFileFlock(int fd G_GNUC_UNUSED, - bool lock G_GNUC_UNUSED, - bool shared G_GNUC_UNUSED) -{ - errno = ENOSYS; - return -1; -} - #endif /* WIN32 */ diff --git a/src/util/virfile.h b/src/util/virfile.h index cb0e586a7d11..2eec89598f6b 100644 --- a/src/util/virfile.h +++ b/src/util/virfile.h @@ -118,8 +118,6 @@ int virFileLock(int fd, bool shared, off_t start, off_t len, bool waitForLock) int virFileUnlock(int fd, off_t start, off_t len) G_GNUC_NO_INLINE; -int virFileFlock(int fd, bool lock, bool shared); - typedef int (*virFileRewriteFunc)(int fd, const void *opaque); int virFileRewrite(const char *path, mode_t mode, diff --git a/src/util/virresctrl.c b/src/util/virresctrl.c index 9b78a6cb159b..2129630a190f 100644 --- a/src/util/virresctrl.c +++ b/src/util/virresctrl.c @@ -456,6 +456,8 @@ VIR_ONCE_GLOBAL_INIT(virResctrl); static int virResctrlLockWrite(void) { +#ifndef WIN32 + int fd = open(SYSFS_RESCTRL_PATH, O_RDONLY | O_CLOEXEC); if (fd < 0) { @@ -463,13 +465,20 @@ virResctrlLockWrite(void) return -1; } - if (virFileFlock(fd, true, false) < 0) { + if (flock(fd, LOCK_EX) < 0) { virReportSystemError(errno, "%s", _("Cannot lock resctrl")); VIR_FORCE_CLOSE(fd); return -1; } return fd; + +#else /* WIN32 */ + + virReportSystemError(ENOSYS, "%s", _("Cannot lock resctrl")); + return -1; + +#endif } @@ -484,10 +493,14 @@ virResctrlUnlock(int fd) if (VIR_CLOSE(fd) < 0) { virReportSystemError(errno, "%s", _("Cannot close resctrl")); +#ifndef WIN32 + /* Trying to save the already broken */ - if (virFileFlock(fd, false, false) < 0) + if (flock(fd, LOCK_UN) < 0) virReportSystemError(errno, "%s", _("Cannot unlock resctrl")); +#endif + return -1; } -- 2.28.0

On a Wednesday in 2020, Andrea Bolognani wrote: Yes, please. With that, the whole series: Reviewed-by: Ján Tomko <jtomko(a)redhat.com&gt; Jano

On Wed, Jul 29, 2020 at 02:20:50PM +0200, Andrea Bolognani wrote: Well, in case they get any similar feature (since it is actually Intel-only AFAIK) I just wanted to stub it out only for platforms where flock(2) is not available.

There is no distinction between Read/Write locks for resctrl from libvirt's point of view any more. Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; --- src/util/virresctrl.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/util/virresctrl.c b/src/util/virresctrl.c index 2129630a190f..954e4fd506f7 100644 --- a/src/util/virresctrl.c +++ b/src/util/virresctrl.c @@ -454,7 +454,7 @@ VIR_ONCE_GLOBAL_INIT(virResctrl); /* Common functions */ static int -virResctrlLockWrite(void) +virResctrlLock(void) { #ifndef WIN32 @@ -2404,7 +2404,7 @@ virResctrlAllocCreate(virResctrlInfoPtr resctrl, if (STREQ(alloc->path, SYSFS_RESCTRL_PATH)) return 0; - lockfd = virResctrlLockWrite(); + lockfd = virResctrlLock(); if (lockfd < 0) goto cleanup; @@ -2597,7 +2597,7 @@ virResctrlMonitorCreate(virResctrlMonitorPtr monitor, if (virResctrlMonitorDeterminePath(monitor, machinename) < 0) return -1; - lockfd = virResctrlLockWrite(); + lockfd = virResctrlLock(); if (lockfd < 0) return -1; -- 2.28.0