cpu-timers: Cleanup arm_timer()

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 35 insertions, 69 deletions

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index d01e0a348e61..7c7166f766cc 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -547,97 +547,63 @@ static inline int expires_gt(cputime_t expires, cputime_t new_exp)
                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
  * for reading, and interrupts disabled.
  */
-static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
+static void arm_timer(struct k_itimer *timer)
 {
         struct task_struct *p = timer->it.cpu.task;
         struct list_head *head, *listpos;
+        struct task_cputime *cputime_expires;
         struct cpu_timer_list *const nt = &timer->it.cpu;
         struct cpu_timer_list *next;
 
-        head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
-                p->cpu_timers : p->signal->cpu_timers);
+        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
+                head = p->cpu_timers;
+                cputime_expires = &p->cputime_expires;
+        } else {
+                head = p->signal->cpu_timers;
+                cputime_expires = &p->signal->cputime_expires;
+        }
         head += CPUCLOCK_WHICH(timer->it_clock);
 
         BUG_ON(!irqs_disabled());
         spin_lock(&p->sighand->siglock);
 
         listpos = head;
-        if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
-                list_for_each_entry(next, head, entry) {
-                        if (next->expires.sched > nt->expires.sched)
-                                break;
-                        listpos = &next->entry;
-                }
-        } else {
-                list_for_each_entry(next, head, entry) {
-                        if (cputime_gt(next->expires.cpu, nt->expires.cpu))
-                                break;
-                        listpos = &next->entry;
-                }
+        list_for_each_entry(next, head, entry) {
+                if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
+                        break;
+                listpos = &next->entry;
         }
         list_add(&nt->entry, listpos);
 
         if (listpos == head) {
+                union cpu_time_count *exp = &nt->expires;
+
                 /*
-                 * We are the new earliest-expiring timer.
-                 * If we are a thread timer, there can always
-                 * be a process timer telling us to stop earlier.
+                 * We are the new earliest-expiring POSIX 1.b timer, hence
+                 * need to update expiration cache. Take into account that
+                 * for process timers we share expiration cache with itimers
+                 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
                  */
 
-                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 (expires_gt(p->cputime_expires.prof_exp,
-                                               exp->cpu))
-                                        p->cputime_expires.prof_exp = exp->cpu;
-                                break;
-                        case CPUCLOCK_VIRT:
-                                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 > exp->sched)
-                                        p->cputime_expires.sched_exp =
-                                                                exp->sched;
-                                break;
-                        }
-                } else {
-                        struct signal_struct *const sig = p->signal;
-                        union cpu_time_count *exp = &timer->it.cpu.expires;
-
-                        /*
-                         * For a process timer, set the cached expiration time.
-                         */
-                        switch (CPUCLOCK_WHICH(timer->it_clock)) {
-                        default:
-                                BUG();
-                        case CPUCLOCK_VIRT:
-                                if (expires_gt(sig->cputime_expires.virt_exp, exp->cpu))
-                                        sig->cputime_expires.virt_exp = exp->cpu;
-                        case CPUCLOCK_PROF:
-                                if (expires_gt(sig->cputime_expires.prof_exp, exp->cpu))
-                                        sig->cputime_expires.prof_exp = exp->cpu;
-                                break;
-                        case CPUCLOCK_SCHED:
-                                sig->cputime_expires.sched_exp = exp->sched;
-                                break;
-                        }
+                switch (CPUCLOCK_WHICH(timer->it_clock)) {
+                case CPUCLOCK_PROF:
+                        if (expires_gt(cputime_expires->prof_exp, exp->cpu))
+                                cputime_expires->prof_exp = exp->cpu;
+                        break;
+                case CPUCLOCK_VIRT:
+                        if (expires_gt(cputime_expires->virt_exp, exp->cpu))
+                                cputime_expires->virt_exp = exp->cpu;
+                        break;
+                case CPUCLOCK_SCHED:
+                        if (cputime_expires->sched_exp == 0 ||
+                            cputime_expires->sched_exp > exp->sched)
+                                cputime_expires->sched_exp = exp->sched;
+                        break;
                 }
         }
 
@@ -819,7 +785,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
         if (new_expires.sched != 0 &&
             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
             cpu_time_before(timer->it_clock, val, new_expires)) {
-                arm_timer(timer, val);
+                arm_timer(timer);
         }
 
         read_unlock(&tasklist_lock);
@@ -1283,7 +1249,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
         /*
          * Now re-arm for the new expiry time.
          */
-        arm_timer(timer, now);
+        arm_timer(timer);
 
 out_unlock:
         read_unlock(&tasklist_lock);