On Tue, 28 Oct 2008, Nigel Cunningham wrote: > The answer is to freeze the fuse filesystems first, stopping new > requests (freezing the processes making them) before they are passed on > to userspace and allowing existing requests to complete or freeze. Once > that is done, the userspace fuse processes will be idle, at least as far > as fuse activity is concerned. After fuse activity is stopped, userspace > can be frozen without worrying about what processes are fuse and what > aren't. This is what my patch implements so far. OK. > To deal with requests that are already in progress, I'd suggest three > possibilities, in the order I think they should be preferred. > > 1) Use wait_event_freezeable[_timeout] in fuse code. Probably preferable > to #2, but I thought of it later :) > > 2) Use freezer_do_not_count as part of FUSE_MIGHT_FREEZE (resetting > before exiting the callers, of course). If the request doesn't complete > during the freezing period, it must be because the userspace thread was > already frozen. If the request does complete, we're counted again during > the normal freezing of userspace that follows the freezing of > filesystems. > > 3) Adding a means to check whether processes being frozen are fuse > requests. The code could then wait for fc->num_waiting - (say) > fc->num_frozen == 0. Yup, these fix the freezing of tasks which have outstanding fuse requests. However it does not fix the freezing of tasks which are waiting for VFS locks (i.e. inode->i_mutex) held by the outstanding fuse requests. This is the tricky part... Miklos _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
