cpu-timers: Simplify RLIMIT_CPU handling

Let always set signal->cputime_expires expiration cache when setting
new itimer, POSIX 1.b timer, and RLIMIT_CPU.  Since we are
initializing prof_exp expiration cache during fork(), this allows to
remove "RLIMIT_CPU != inf" check from fastpath_timer_check() and do
some other cleanups.

Checked against regression using test cases from:
http://marc.info/?l=linux-kernel&m=123749066504641&w=4
http://marc.info/?l=linux-kernel&m=123811277916642&w=2

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>

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 1a22dfd..d01e0a3 100644 (file)
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -11,19 +11,18 @@
 #include <trace/events/timer.h>
 
 /*
- * Called after updating RLIMIT_CPU to set timer expiration if necessary.
+ * Called after updating RLIMIT_CPU to run cpu timer and update
+ * tsk->signal->cputime_expires expiration cache if necessary. Needs
+ * siglock protection since other code may update expiration cache as
+ * well.
  */
 void update_rlimit_cpu(unsigned long rlim_new)
 {
        cputime_t cputime = secs_to_cputime(rlim_new);
-       struct signal_struct *const sig = current->signal;
 
-       if (cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) ||
-           cputime_gt(sig->it[CPUCLOCK_PROF].expires, cputime)) {
-               spin_lock_irq(&current->sighand->siglock);
-               set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
-               spin_unlock_irq(&current->sighand->siglock);
-       }
+       spin_lock_irq(&current->sighand->siglock);
+       set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
+       spin_unlock_irq(&current->sighand->siglock);
 }
 
 static int check_clock(const clockid_t which_clock)
@@ -564,7 +563,6 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
        struct list_head *head, *listpos;
        struct cpu_timer_list *const nt = &timer->it.cpu;
        struct cpu_timer_list *next;
-       unsigned long i;
 
        head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
                p->cpu_timers : p->signal->cpu_timers);
@@ -630,20 +628,11 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
                        default:
                                BUG();
                        case CPUCLOCK_VIRT:
-                               if (expires_le(sig->it[CPUCLOCK_VIRT].expires,
-                                              exp->cpu))
-                                       break;
-                               sig->cputime_expires.virt_exp = exp->cpu;
-                               break;
+                               if (expires_gt(sig->cputime_expires.virt_exp, exp->cpu))
+                                       sig->cputime_expires.virt_exp = exp->cpu;
                        case CPUCLOCK_PROF:
-                               if (expires_le(sig->it[CPUCLOCK_PROF].expires,
-                                              exp->cpu))
-                                       break;
-                               i = sig->rlim[RLIMIT_CPU].rlim_cur;
-                               if (i != RLIM_INFINITY &&
-                                   i <= cputime_to_secs(exp->cpu))
-                                       break;
-                               sig->cputime_expires.prof_exp = exp->cpu;
+                               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;
@@ -1386,7 +1375,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
                        return 1;
        }
 
-       return sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY;
+       return 0;
 }
 
 /*
@@ -1452,21 +1441,23 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 }
 
 /*
- * Set one of the process-wide special case CPU timers.
+ * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
  * The tsk->sighand->siglock must be held by the caller.
- * The *newval argument is relative and we update it to be absolute, *oldval
- * is absolute and we update it to be relative.
  */
 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
                           cputime_t *newval, cputime_t *oldval)
 {
        union cpu_time_count now;
-       struct list_head *head;
 
        BUG_ON(clock_idx == CPUCLOCK_SCHED);
        cpu_timer_sample_group(clock_idx, tsk, &now);
 
        if (oldval) {
+               /*
+                * We are setting itimer. The *oldval is absolute and we update
+                * it to be relative, *newval argument is relative and we update
+                * it to be absolute.
+                */
                if (!cputime_eq(*oldval, cputime_zero)) {
                        if (cputime_le(*oldval, now.cpu)) {
                                /* Just about to fire. */
@@ -1479,33 +1470,21 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
                if (cputime_eq(*newval, cputime_zero))
                        return;
                *newval = cputime_add(*newval, now.cpu);
-
-               /*
-                * If the RLIMIT_CPU timer will expire before the
-                * ITIMER_PROF timer, we have nothing else to do.
-                */
-               if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
-                   < cputime_to_secs(*newval))
-                       return;
        }
 
        /*
-        * Check whether there are any process timers already set to fire
-        * before this one.  If so, we don't have anything more to do.
+        * Update expiration cache if we are the earliest timer, or eventually
+        * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
         */
-       head = &tsk->signal->cpu_timers[clock_idx];
-       if (list_empty(head) ||
-           cputime_ge(list_first_entry(head,
-                                 struct cpu_timer_list, entry)->expires.cpu,
-                      *newval)) {
-               switch (clock_idx) {
-               case CPUCLOCK_PROF:
+       switch (clock_idx) {
+       case CPUCLOCK_PROF:
+               if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
                        tsk->signal->cputime_expires.prof_exp = *newval;
-                       break;
-               case CPUCLOCK_VIRT:
+               break;
+       case CPUCLOCK_VIRT:
+               if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
                        tsk->signal->cputime_expires.virt_exp = *newval;
-                       break;
-               }
+               break;
        }
 }