2.6.8.1: xtime value may become incorrect

2.6.8.1: xtime value may become incorrect

[Vladimir Grouzdev]

    The xtime value may become incorrect when the
    update_wall_time(ticks) function is called with "ticks" > 1.
    In such a case, the xtime variable is updated multiple times
    inside the loop but it is normalized only once outside of
    the loop.

    This bug was reported at:

    http://bugme.osdl.org/show_bug.cgi?id=3403

    Patch to fix the problem:

diff -Nrca linux-2.6.8.1/kernel/timer.c linux-2.6.8.1-patched/kernel/timer.c
*** linux-2.6.8.1/kernel/timer.c    2004-08-14 12:56:00.000000000 +0200
--- linux-2.6.8.1-patched/kernel/timer.c    2004-09-27 
16:24:48.000000000 +0200
***************
*** 776,788 ****
      do {
          ticks--;
          update_wall_time_one_tick();
      } while (ticks);
-
-     if (xtime.tv_nsec >= 1000000000) {
-         xtime.tv_nsec -= 1000000000;
-         xtime.tv_sec++;
-         second_overflow();
-     }
  }
 
  static inline void do_process_times(struct task_struct *p,
--- 776,787 ----
      do {
          ticks--;
          update_wall_time_one_tick();
+         if (xtime.tv_nsec >= 1000000000) {
+             xtime.tv_nsec -= 1000000000;
+             xtime.tv_sec++;
+             second_overflow();
+         }
      } while (ticks);
  }
 
  static inline void do_process_times(struct task_struct *p,

Re: 2.6.8.1: xtime value may become incorrect

[john stultz]

On Mon, 2004-09-27 at 08:22, Vladimir Grouzdev wrote:
>     The xtime value may become incorrect when the
>     update_wall_time(ticks) function is called with "ticks" > 1.
>     In such a case, the xtime variable is updated multiple times
>     inside the loop but it is normalized only once outside of
>     the loop.

Vladimir, 
	This looks like a good patch to me. If no one else has any complaints,
send it on to Andrew.

thanks!
-john