ebiederm at xmission.com (Eric W. Biederman) writes: > Andrew Morton <akpm at osdl.org> writes: > >> So in general, yes, the driver should be converted to the kthread API - >> this is a requirement for virtualisation, but I forget why, and that's the >> "standard" way of doing it. > > With the kthread api new kernel threads are started as children of keventd > in well defined circumstances. If you don't do this kernel threads > can wind up sharing weird parts of a parent process's resources and > locking resources in the kernel long past the time when they are > actually used by anything a user space process can kill. > > We have actually witnessed this problem with the kernels filesystem mount > namespace. Mostly daemonize in the kernel unshares everything that > could be a problem but the problem is sufficiently subtle it makes > more sense to the change kernel threads. So these weird and subtle > dependencies go away. > > So in essence the container work needs the new kthread api for the > same reasons everyone else does it is just more pronounced in that > case. That plus the obvious bit. For the pid namespace we have to declare war on people storing a pid_t values. Either converting them to struct pid * or removing them entirely. Doing the kernel_thread to kthread conversion removes them entirely. Eric
