Am Donnerstag, 5. Juli 2007 schrieb Miklos Szeredi: > > > > > > I have discussed the benefits elsewhere. As for the deadlocks -- do > > > > > > you still observe them if you use the version of the freezer which > > > > > > doesn't freeze kernel threads? > > > > > > > > > > In general the only way to guarantee there are no deadlocks is to > > > > > construct the graph of dependencies between tasks. Those dependencies > > > > > are not in practice observable from outside the tasks, so it is > > > > > virtually impossible to construct the graph. > > > > > > > > In which way can user space tasks depend on each other in a way that > > > > allows a them members of that cycle to be in uninterruptible sleep? > > > > > > - process A calls rename() on a fuse fs > > > - process B, the fuse server, starts to process the rename request > > > - process B is frozen before it can reply > > > > > > Now process A is unfreezable. We cannot make rename() restartable, > > > hence it cannot be interruptible. > > > > Then this is a problem specific to fuse. You should teach fuse to block > > suspension while such operations are being performed. > > And teach VFS to block suspension, while waiting on a mutex held by > another process performing a fuse operation. > > I can already hear the beautiful praise from Al Viro at the sight of > that ;) There is that. OK, bite the bullet. Tasks involved in fuse are special. Give them a flag and teach the freezer to put them on ice only after all other task are frozen. In a way they are kernel, there's no use denying that. Regards Oliver _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
