aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/posix-cpu-timers.c
diff options
context:
space:
mode:
authorStanislaw Gruszka <sgruszka@redhat.com>2009-07-29 12:15:27 +0200
committerIngo Molnar <mingo@elte.hu>2009-08-03 14:48:35 +0200
commit8356b5f9c424e5831715abbce747197c30d1fd71 (patch)
tree87de74cc86f6eebf88eba9a4c335614787d984c5 /kernel/posix-cpu-timers.c
parent42c4ab41a176ee784c0f28c0b29025a8fc34f05a (diff)
downloadmrst-s0i3-test-8356b5f9c424e5831715abbce747197c30d1fd71.tar.gz
mrst-s0i3-test-8356b5f9c424e5831715abbce747197c30d1fd71.tar.xz
mrst-s0i3-test-8356b5f9c424e5831715abbce747197c30d1fd71.zip
itimers: Fix periodic tics precision
Measure ITIMER_PROF and ITIMER_VIRT timers interval error between real ticks and requested by user. Take it into account when scheduling next tick. This patch introduce possibility where time between two consecutive tics is smaller then requested interval, it preserve however dependency that n tick is generated not earlier than n*interval time - counting from the beginning of periodic signal generation. 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: <1248862529-6063-3-git-send-email-sgruszka@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/posix-cpu-timers.c')
-rw-r--r--kernel/posix-cpu-timers.c20
1 files changed, 17 insertions, 3 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 9b2d5e4dc8c..b60d644ea4b 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);