On Friday, 6 July 2007 00:04, Pavel Machek wrote: > Hi! > > > > > > > > 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. > > > > > > Yes, we are claiming fuse is very special in this regard, and perhaps > > > even broken. > > > > > > Let's see. If I SIGSTOP the fuse server, I can get unrelated tasks > > > unkillable (even for SIGKILL!) forever. > > > > Actually fuse allows SIGKILL, because it's always fatal, and the > > syscall may not be restarted. > > Okay, and you should handle refrigerator in the same paths where you > handle SIGKILL. Just add try_to_freeze() there... In fact the problem is more complicated than that, because some tasks may be waiting on VFS locks related to FUSE. Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
