On Mon, Jul 24, 2017 at 01:12:59PM -0400, John Ferlan wrote:
On 07/19/2017 10:31 AM, Michal Privoznik wrote:
We already have virRWLockInit. But this uses pthread defaults which prefer reader to initialize the RW lock. This may lead to writer starvation. Therefore we need to have the counterpart that prefers writers. Now, according to the pthread_rwlockattr_setkind_np() man page setting PTHREAD_RWLOCK_PREFER_WRITER_NP attribute is no-op. Therefore we need to use PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP attribute. So much for good enum value names.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/libvirt_private.syms | 1 + src/util/virthread.c | 35 +++++++++++++++++++++++++++++++++++ src/util/virthread.h | 1 + 3 files changed, 37 insertions(+)
This has broken the CI build, freebsd is not happy:
../../src/util/virthread.c:133:42: error: use of undeclared identifier 'PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP' pthread_rwlockattr_setkind_np(&attr, PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP); ^ 1 error generated.
It is not just FreeBSD, it also breaks OS-X and Win32. The suffix '_np' / '_NP' is shorthand for nNon portable" - these are glibc inventions. IMHO we should not really use this in our code as if we're going to make assumptions that writers are not starved as a result, because writers will be starved on any non-Linux platform. IOW, I think we need to just revert this. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|