lkml.org 
[lkml]   [2014]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4 2/5] x86,entry: Only call user_exit if TIF_NOHZ
On 07/28, Andy Lutomirski wrote:
>
> @@ -1449,7 +1449,12 @@ long syscall_trace_enter(struct pt_regs *regs)
> {
> long ret = 0;
>
> - user_exit();
> + /*
> + * If TIF_NOHZ is set, we are required to call user_exit() before
> + * doing anything that could touch RCU.
> + */
> + if (test_thread_flag(TIF_NOHZ))
> + user_exit();

Personally I still think this change just adds more confusion, but I leave
this to you and Frederic.

It is not that "If TIF_NOHZ is set, we are required to call user_exit()", we
need to call user_exit() just because we enter the kernel. TIF_NOHZ is just
the implementation detail which triggers this slow path.

At least it should be correct, unless I am confused even more than I think.

Oleg.



\
 
 \ /
  Last update: 2014-07-29 22:01    [W:0.091 / U:3.812 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site