On Friday, 1 December 2006 23:07, Alan Stern wrote: > On Fri, 1 Dec 2006, Rafael J. Wysocki wrote: > > > Well, the current code does exactly the same - it freezes userland tasks > > by sending them fake signals (and there's no way to check if such a process > > holds any locks at that time). Moreover, it's been doing that from day one > > and my patch doesn't change that. > > Obviously the scenario I described is very unlikely. It would depend on > a user program doing exactly the wrong thing at the wrong time, _and_ > using a USB mass storage device for swapping, _and_ getting an I/O error > while reading or writing the memory image. > > > If you have an unfreezeable process that depends on locks that may be held > > by userland tasks, then _this_ is a bug, IMHO. > > In this case it isn't absolute dependence. If usb-storage isn't able to > obtain the lock it needs, then it times out after 1 second and simply > doesn't reset the device. Well, I think as long as the system can recover, it's all fine. > Still, you would have your work cut out trying to find all the places in > the kernel where an unfreezable process takes a lock which might be held > by a user process. For instance, I doubt that all the workqueue threads > could pass this test. Fortunately such problems have never been reported, so we can postpone the hunt for these places a little. ;-) But seriously, they are potentially dangerous with the current code, so in fact we'll need to have a look at them at some point in the future. Greetings, Rafael -- You never change things by fighting the existing reality. R. Buckminster Fuller
