On Sat, 21 Feb 2015, Ingo Molnar wrote: > (It does have some other requirements, such as making all > syscalls interruptible to a 'special' signalling method > that only live patching triggers - even syscalls that are > under the normal ABI uninterruptible, such as sys_sync().) BTW I didn't really understand this -- could you please elaborate what exactly do you propose to do here in your "simplified" patching method (i.e. serializing everybody at the kernel boundary) for TASK_UNINTERRUPTIBLE processess? That actually seems to be the most crucial problem to me in this respect. Other things are rather implementation details; no matter whether we are sending normal SIGCONT or SIGPATCHING with special semantics you have described above, at the end of the day we end up calling kick_process() for the task in question, and that makes both interruptible sleepers and CPU hogs go through the "checkpoint". SIGPATCHING would then be "just" an improvement of this, making sure that EINTR doesn't spuriously get leaked to userspace. But I didn't understand your claims regarding uninterruptible sleeps in your paragraph above. sys_sync() is one thing, that's just waiting uninterruptibly for completion. But how about all the mutex waitiers in TASK_UNINTERRUPTIBLE, for example? Thanks a lot, -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
