Dear Paul, thank you for feedback. FYI, we are using perfbook as a main reference in our discipline. 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
