cputime: Safely read cputime of full dynticks CPUs

While remotely reading the cputime of a task running in a
full dynticks CPU, the values stored in utime/stime fields
of struct task_struct may be stale. Its values may be those
of the last kernel <-> user transition time snapshot and
we need to add the tickless time spent since this snapshot.

To fix this, flush the cputime of the dynticks CPUs on
kernel <-> user transition and record the time / context
where we did this. Then on top of this snapshot and the current
time, perform the fixup on the reader side from task_times()
accessors.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[fixed kvm module related build errors]
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index ed567babe789..f5cc25f147a6 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -221,7 +221,7 @@ asmlinkage void __do_softirq(void)
         current->flags &= ~PF_MEMALLOC;
 
         pending = local_softirq_pending();
-        vtime_account_irq_enter(current);
+        account_irq_enter_time(current);
 
         __local_bh_disable((unsigned long)__builtin_return_address(0),
                                 SOFTIRQ_OFFSET);
@@ -272,7 +272,7 @@ restart:
 
         lockdep_softirq_exit();
 
-        vtime_account_irq_exit(current);
+        account_irq_exit_time(current);
         __local_bh_enable(SOFTIRQ_OFFSET);
         tsk_restore_flags(current, old_flags, PF_MEMALLOC);
 }
@@ -341,7 +341,7 @@ static inline void invoke_softirq(void)
  */
 void irq_exit(void)
 {
-        vtime_account_irq_exit(current);
+        account_irq_exit_time(current);
         trace_hardirq_exit();
         sub_preempt_count(IRQ_EXIT_OFFSET);
         if (!in_interrupt() && local_softirq_pending())