cpu-timers: Return correct previous timer reload value
Stanislaw Gruszka [Thu, 11 Mar 2010 22:04:39 +0000 (14:04 -0800)]
According POSIX we need to correctly set old timer it_interval value when
user request that in timer_settime().  Tested using below program.

 #include <sys/time.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include <unistd.h>
 #include <assert.h>

 int main(void)
 {
struct sigaction act;
struct sigevent evt = { };
timer_t tid;
struct itimerspec spec, u_spec, k_spec;

evt.sigev_notify = SIGEV_SIGNAL;
evt.sigev_signo = SIGPROF;
assert(timer_create(CLOCK_PROCESS_CPUTIME_ID, &evt,  &tid) == 0);

spec.it_value.tv_sec = 1;
spec.it_value.tv_nsec = 2;
spec.it_interval.tv_sec = 3;
spec.it_interval.tv_nsec = 4;
u_spec = spec;
assert(timer_settime(tid, 0, &spec,  NULL) == 0);

spec.it_value.tv_sec = 5;
spec.it_value.tv_nsec = 6;
spec.it_interval.tv_sec = 7;
spec.it_interval.tv_nsec = 8;
assert(timer_settime(tid, 0, &spec,  &k_spec) == 0);

 #define PRT(val) printf(#val ":\t%d/%d\n", (int) u_spec.val, (int) k_spec.val)
PRT(it_value.tv_sec);
PRT(it_value.tv_nsec);
PRT(it_interval.tv_sec);
PRT(it_interval.tv_nsec);

return 0;
 }

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>

kernel/posix-cpu-timers.c

index 7c7166f..cce2f0b 100644 (file)
@@ -676,7 +676,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
                        struct itimerspec *new, struct itimerspec *old)
 {
        struct task_struct *p = timer->it.cpu.task;
-       union cpu_time_count old_expires, new_expires, val;
+       union cpu_time_count old_expires, new_expires, old_incr, val;
        int ret;
 
        if (unlikely(p == NULL)) {
@@ -707,6 +707,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
        BUG_ON(!irqs_disabled());
 
        ret = 0;
+       old_incr = timer->it.cpu.incr;
        spin_lock(&p->sighand->siglock);
        old_expires = timer->it.cpu.expires;
        if (unlikely(timer->it.cpu.firing)) {
@@ -822,7 +823,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
  out:
        if (old) {
                sample_to_timespec(timer->it_clock,
-                                  timer->it.cpu.incr, &old->it_interval);
+                                  old_incr, &old->it_interval);
        }
        return ret;
 }