1 files changed, 17 insertions, 3 deletions

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 9b2d5e4dc8c4..b60d644ea4b3 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1070,6 +1070,8 @@ static void stop_process_timers(struct task_struct *tsk)
         spin_unlock_irqrestore(&cputimer->lock, flags);
 }
 
+static u32 onecputick;
+
 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
                              cputime_t *expires, cputime_t cur_time, int signo)
 {
@@ -1077,9 +1079,16 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
                 return;
 
         if (cputime_ge(cur_time, it->expires)) {
-                it->expires = it->incr;
-                if (!cputime_eq(it->expires, cputime_zero))
-                        it->expires = cputime_add(it->expires, cur_time);
+                if (!cputime_eq(it->incr, cputime_zero)) {
+                        it->expires = cputime_add(it->expires, it->incr);
+                        it->error += it->incr_error;
+                        if (it->error >= onecputick) {
+                                it->expires = cputime_sub(it->expires,
+                                                        jiffies_to_cputime(1));
+                                it->error -= onecputick;
+                        }
+                } else
+                        it->expires = cputime_zero;
 
                 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
         }
@@ -1696,10 +1705,15 @@ static __init int init_posix_cpu_timers(void)
                 .nsleep = thread_cpu_nsleep,
                 .nsleep_restart = thread_cpu_nsleep_restart,
         };
+        struct timespec ts;
 
         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
+        cputime_to_timespec(jiffies_to_cputime(1), &ts);
+        onecputick = ts.tv_nsec;
+        WARN_ON(ts.tv_sec != 0);
+
         return 0;
 }
 __initcall(init_posix_cpu_timers);