On Sun, May 10, 2015 at 09:42:53PM -0300, Jose Fernando Santos de Carvalho wrote: > Dear Paul, > thank you for feedback. FYI, we are using perfbook as a main reference > in our discipline. Hello, Jose, That is very good to hear, and thank you for letting me know! Thanx, Paul > best regards. > > > On Sun, May 10, 2015 at 5:49 PM, Paul E. McKenney > <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > On Sat, May 09, 2015 at 12:01:01PM -0300, Jose Fernando Santos de Carvalho wrote: > >> Link: http://ustore1.rnp.br/ustore/faces/publicFile.xhtml?code=35e4c269403136c4a9fdb9227b704409 > >> > >> On Tue, May 5, 2015 at 11:40 PM, Jose Fernando Santos de Carvalho > >> <jfsc@xxxxxxxxxxx> wrote: > >> > Dear all, > >> > > >> > while writing chapter 6 (Partitioning and Synchronisation Design), Paul has > >> > presented five special cases about Left - and Right-Hand Locks(Figure 6.5). > >> > However, it is not clear for me the possible problem in the fourth case > >> > (link). > >> > > >> > > >> > If possible, could anyone send some feedback about it? > >> > > >> > Link: > >> > http://ustore1.rnp.br/ustore/faces/publicFile.xhtml?code=35e4c269403136c4a9fdb9227b704409-- > >> > > >> > -- > >> > Jose Fernando > > > > Hello, Jose, > > > > You could indeed claim that the second-to-last row is safe because the two > > ends will be operating on different pointers for element 1. Nevertheless, > > the fact remains that both ends need to operate on element 1 simultaneously, > > which should give us pause. Especially given that we are in a concurrent > > environment. > > > > For example, suppose that thread A holds the left-hand lock and wants to > > remove element 0. While thread A is comtemplating doing this, some other > > thread B might hold the right-hand lock and remove element 2. We are now > > in the state shown in the third row, and thus completely unsafe. > > > > Thanx, Paul > > > > > > -- > -- > José Fernando Carvalho > DSc Candidate in Computer Science > Federal University of Pernambuco (UFPE) - Brazil > -- To unsubscribe from this list: send the line "unsubscribe perfbook" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
