On Friday 13 January 2006 05:20 am, prime wrote: > On 1/13/06, Kamal R. Prasad <[EMAIL PROTECTED]> wrote: > > Priority need not be propagated to readers as they will not block other > > readers. > > Most likely, you only need to propagate to the writer to avoid priority > > inversron. > > > > regards > > -kamal > > > > On 1/13/06, prime <[EMAIL PROTECTED]> wrote: > > > Hi hackers, > > > I have a question about how priority propagation works on > > > read/write lock.On locks that have only one owner at a determinate > > > moment,we can simply propagate the priority to the owner of lock,but > > > read/write lock may have many owners at some time,so how can we know > > > who are the owners? > > > I browse the OpenSolaris' read/write lock implementation,and find > > > that, it simply treats the owner of the lock as NULL when readers own > > > the read/write lock.In this way,we can not propagate our priority to > > > all threads that block us. > > > > > > Thanks very much. > > > -- > > > Three passions, simple but overwhelmingly strong, have governed my > > > life: > > > > > > the longing for love, the search for knowledge, and unbearable pity for > > > the suffering of mankind. > > > ---------Bertrand Russell > > > _______________________________________________ > > > freebsd-hackers@freebsd.org mailing list > > > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > > > To unsubscribe, send any mail to > > > "[EMAIL PROTECTED] " > > Thanks your reply. > But readers may block writers, aren't they? > For example, there are three threads,A,B and C, and a read/write lock > rwlock1 ,and a mutex mtx1. > 1.A lock mtx1, > 2.B get the read lock of rwlock1 and then want > to get mtx1,but mtx1 is locked by A,so B has to > wait on mtx1. > 3.C want to get the write lock of rwlock1 and it > has to wait,because rwlock1 is read locked by B. > Now if C's priority < A's priority(in numerical), then we get priority > inversion. > > How can avoid this priority inversion? > Thanks.
I think you just kind of punt and do a best effort. Trying to manage a list of current read lock holders would be a bit PITA. -- John Baldwin <[EMAIL PROTECTED]> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
