[PATCH v3 2/3] util: Get rid of virFileFlock()

[Martin Kletzander]

On Wed, Jul 29, 2020 at 02:20:50PM +0200, Andrea Bolognani wrote:
>On Wed, 2020-07-29 at 13:43 +0200, Martin Kletzander wrote:
>> +++ 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;
>>      }
>
>So in the end you decided to go for the nuclear option :D
>
>I'm okay with the approach, but I would prefer if you stubbed out the
>functions completely, eg.
>
>  #ifndef WIN32
>
>  static int
>  virResctrlLockWrite(void)
>  {
>      /* do stuff */
>  }
>
>  static int
>  virResctrlUnlock(int fd)
>  {
>      /* do stuff */
>  }
>
>  #else
>
>  static int
>  virResctrlLockWrite(void)
>  {
>      virReportSystemError(ENOSYS, "%s",
>                           _("resctrl locking is not supported "
>                             "on this platform"));
>      return -1;
>  }
>
>  static int
>  virResctrlUnlock(int fd)
>  {
>      virReportSystemError(ENOSYS, "%s",
>                           _("resctrl locking is not supported "
>                             "on this platform"));
>      return -1;
>  }
>
>  #endif
>
>Also, since AFAIU resctrl is Linux-only, perhaps a better
>preprocessor guard would be
>
>  #ifdef __linux__
>
>so that we (correctly) stub the functions out on FreeBSD and macOS
>too.
>

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.

>--
>Andrea Bolognani / Red Hat / Virtualization
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20200729/beba407d/attachment-0001.sig>