[lkml]   [2014]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC] [PATCH] Pre-emption control for userspace
On 03/04, Khalid Aziz wrote:
> On 03/04/2014 12:03 PM, Oleg Nesterov wrote:
>> 1. mremap() can move this vma, so do_exit() can't trust ->uaddr
>> 2. Even worse, mremap() itself is not safe. It can do ->close()
>> too and create the new vma with the same vm_ops. Another
>> unmap from (say) exit_mm() won't be happy.
> I agree this looks like a potential spot for trouble. I was asking if
> removing sys_munmap() of uaddr from do_exit() solves both of the above
> problems?

How? Of course this won't solve the problems. And there are more problems.

> You have convinced me this sys_munmap() I added is unnecessary.

Cough ;) I didn't try to convince you that it should be removed. It is
necessary (but of course you should not use sys_munmap(), say vm_munmap
is better.

But you know, I think this all doesn't matter. Imho, this proc/mmap
interface is horrible. Perhaps something like tls area visible to kernel
make sense, but it should be more generic at least.

You added /proc/sched_preempt_delay to avoid the syscall. I think it
would be better to simply add vdso_sched_preempt_delay() instead.

But the main problem, of course, is that this feature is questionable.


 \ /
  Last update: 2014-03-09 17:01    [W:0.131 / U:2.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site