itimers: Simplify arm_timer() code a bit

Don't update values in expiration cache when new ones are
equal. Add expire_le() and expire_gt() helpers to simplify the
code.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-4-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 23 insertions, 21 deletions

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index b60d644ea4b3..69c92374355f 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -541,6 +541,17 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
                                              now);
 }
 
+static inline int expires_gt(cputime_t expires, cputime_t new_exp)
+{
+        return cputime_eq(expires, cputime_zero) ||
+               cputime_gt(expires, new_exp);
+}
+
+static inline int expires_le(cputime_t expires, cputime_t new_exp)
+{
+        return !cputime_eq(expires, cputime_zero) &&
+               cputime_le(expires, new_exp);
+}
 /*
  * Insert the timer on the appropriate list before any timers that
  * expire later.  This must be called with the tasklist_lock held
@@ -585,31 +596,26 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
                  */
 
                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
+                        union cpu_time_count *exp = &nt->expires;
+
                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
                         default:
                                 BUG();
                         case CPUCLOCK_PROF:
-                                if (cputime_eq(p->cputime_expires.prof_exp,
-                                               cputime_zero) ||
-                                    cputime_gt(p->cputime_expires.prof_exp,
-                                               nt->expires.cpu))
-                                        p->cputime_expires.prof_exp =
-                                                nt->expires.cpu;
+                                if (expires_gt(p->cputime_expires.prof_exp,
+                                               exp->cpu))
+                                        p->cputime_expires.prof_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_VIRT:
-                                if (cputime_eq(p->cputime_expires.virt_exp,
-                                               cputime_zero) ||
-                                    cputime_gt(p->cputime_expires.virt_exp,
-                                               nt->expires.cpu))
-                                        p->cputime_expires.virt_exp =
-                                                nt->expires.cpu;
+                                if (expires_gt(p->cputime_expires.virt_exp,
+                                               exp->cpu))
+                                        p->cputime_expires.virt_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_SCHED:
                                 if (p->cputime_expires.sched_exp == 0 ||
-                                    p->cputime_expires.sched_exp >
-                                                        nt->expires.sched)
+                                    p->cputime_expires.sched_exp > exp->sched)
                                         p->cputime_expires.sched_exp =
-                                                nt->expires.sched;
+                                                                exp->sched;
                                 break;
                         }
                 } else {
@@ -623,17 +629,13 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
                         default:
                                 BUG();
                         case CPUCLOCK_VIRT:
-                                if (!cputime_eq(sig->it[CPUCLOCK_VIRT].expires,
-                                                cputime_zero) &&
-                                    cputime_lt(sig->it[CPUCLOCK_VIRT].expires,
+                                if (expires_le(sig->it[CPUCLOCK_VIRT].expires,
                                                exp->cpu))
                                         break;
                                 sig->cputime_expires.virt_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_PROF:
-                                if (!cputime_eq(sig->it[CPUCLOCK_PROF].expires,
-                                                cputime_zero) &&
-                                    cputime_lt(sig->it[CPUCLOCK_PROF].expires,
+                                if (expires_le(sig->it[CPUCLOCK_PROF].expires,
                                                exp->cpu))
                                         break;
                                 i = sig->rlim[RLIMIT_CPU].rlim_cur;