On Wed 10-09-14 00:23:36, Tejun Heo wrote: > On Tue, Sep 09, 2014 at 05:16:55PM +0200, Michal Hocko wrote: > > But OOM killer doesn't kill kernel threads as they do not own any > > memory. So the check should be safe, no? > > Even for userland tasks, try_to_freeze() can currently be anywhere in > the kernel. The frequently used ones are few but there are some odd
I always thought that user space tasks can be in the fridge only on the way out from the kernel (get_signal_to_deliver). I have quickly greped the code and the only place I can see seems to be run_guest but that one bails out quickly when there are signals pending so it should be safe in this context. cifs is doing something suspicious (cifs_reconnect) but I didn't check more closely all the contexts it is called from. > ones out, and, again, there's nothing enforcing any structure on > try_to_freeze() usage. Would it make sense to have try_to_freeze_user_task or similar and check for kernel thread in try_to_freeze and complain loudly if called from user task context? I mean does it even make sense to call try_to_freeze in the middle of kernel operation for a user task? > The other thing is that we may do quite a bit during exiting including > allocating memory. yes, we can allocate memory and even page fault on the exit path. But TIF_MEMDIE will make sure that the allocation will be successful if there is some memory left. > Are those safe for system PM? Rafael, what exactly are the rules for > PM? What shouldn't change? > > Thanks. > > -- > tejun -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
