From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932230AbYDYSG1 (ORCPT ); Fri, 25 Apr 2008 14:06:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764831AbYDYR5f (ORCPT ); Fri, 25 Apr 2008 13:57:35 -0400 Received: from saraswathi.solana.com ([198.99.130.12]:53147 "EHLO saraswathi.solana.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762694AbYDYR5X (ORCPT ); Fri, 25 Apr 2008 13:57:23 -0400 Date: Fri, 25 Apr 2008 13:56:13 -0400 From: Jeff Dike To: Andrew Morton , LKML , uml-devel Cc: Nix Subject: [PATCH 11/19] UML - Track and make up lost ticks Message-ID: <20080425175613.GA11192@c2.user-mode-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alarm delivery could be noticably late in the !CONFIG_NOHZ case because lost ticks weren't being taken into account. This is now treated more carefully, with the time between ticks being calculated and the appropriate number of ticks delivered to the timekeeping system. Cc: Nix Signed-off-by: Jeff Dike --- arch/um/os-Linux/time.c | 54 ++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 50 insertions(+), 4 deletions(-) Index: linux-2.6-git/arch/um/os-Linux/time.c =================================================================== --- linux-2.6-git.orig/arch/um/os-Linux/time.c 2008-04-25 10:42:12.000000000 -0400 +++ linux-2.6-git/arch/um/os-Linux/time.c 2008-04-25 11:19:26.000000000 -0400 @@ -9,7 +9,9 @@ #include #include #include "kern_constants.h" +#include "kern_util.h" #include "os.h" +#include "process.h" #include "user.h" int set_interval(void) @@ -58,12 +60,17 @@ static inline long long timeval_to_ns(co long long disable_timer(void) { struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } }); + int remain, max = UM_NSEC_PER_SEC / UM_HZ; if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0) printk(UM_KERN_ERR "disable_timer - setitimer failed, " "errno = %d\n", errno); - return timeval_to_ns(&time.it_value); + remain = timeval_to_ns(&time.it_value); + if (remain > max) + remain = max; + + return remain; } long long os_nsecs(void) @@ -79,7 +86,44 @@ static int after_sleep_interval(struct t { return 0; } + +static void deliver_alarm(void) +{ + alarm_handler(SIGVTALRM, NULL); +} + +static unsigned long long sleep_time(unsigned long long nsecs) +{ + return nsecs; +} + #else +unsigned long long last_tick; +unsigned long long skew; + +static void deliver_alarm(void) +{ + unsigned long long this_tick = os_nsecs(); + int one_tick = UM_NSEC_PER_SEC / UM_HZ; + + if (last_tick == 0) + last_tick = this_tick - one_tick; + + skew += this_tick - last_tick; + + while (skew >= one_tick) { + alarm_handler(SIGVTALRM, NULL); + skew -= one_tick; + } + + last_tick = this_tick; +} + +static unsigned long long sleep_time(unsigned long long nsecs) +{ + return nsecs > skew ? nsecs - skew : 0; +} + static inline long long timespec_to_us(const struct timespec *ts) { return ((long long) ts->tv_sec * UM_USEC_PER_SEC) + @@ -102,6 +146,8 @@ static int after_sleep_interval(struct t */ if (start_usecs > usec) start_usecs = usec; + + start_usecs -= skew / UM_NSEC_PER_USEC; tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC, .tv_usec = start_usecs % UM_USEC_PER_SEC }); interval = ((struct itimerval) { { 0, usec }, tv }); @@ -113,8 +159,6 @@ static int after_sleep_interval(struct t } #endif -extern void alarm_handler(int sig, struct sigcontext *sc); - void idle_sleep(unsigned long long nsecs) { struct timespec ts; @@ -126,10 +170,12 @@ void idle_sleep(unsigned long long nsecs */ if (nsecs == 0) nsecs = UM_NSEC_PER_SEC / UM_HZ; + + nsecs = sleep_time(nsecs); ts = ((struct timespec) { .tv_sec = nsecs / UM_NSEC_PER_SEC, .tv_nsec = nsecs % UM_NSEC_PER_SEC }); if (nanosleep(&ts, &ts) == 0) - alarm_handler(SIGVTALRM, NULL); + deliver_alarm(); after_sleep_interval(&ts); }