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 -- 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
