Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763664AbYHEUPd (ORCPT ); Tue, 5 Aug 2008 16:15:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763558AbYHEUO3 (ORCPT ); Tue, 5 Aug 2008 16:14:29 -0400 Received: from saraswathi.solana.com ([198.99.130.12]:48071 "EHLO saraswathi.solana.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761998AbYHEUO2 (ORCPT ); Tue, 5 Aug 2008 16:14:28 -0400 Date: Tue, 5 Aug 2008 16:14:05 -0400 From: Jeff Dike To: stable@kernel.org Cc: LKML , uml-devel Subject: [PATCH 4/14] uml: track and make up lost ticks Message-ID: <20080805201405.GA11784@c2.user-mode-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4524 Lines: 161 >From fe2cc53ee013a4d4d0317d418e7019fe6533a5a8 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/include/process.h | 4 +- arch/um/os-Linux/signal.c | 1 + arch/um/os-Linux/time.c | 54 +++++++++++++++++++++++++++++++++++++++++--- 3 files changed, 53 insertions(+), 6 deletions(-) diff --git a/arch/um/include/process.h b/arch/um/include/process.h index 5af9157..348f8a3 100644 --- a/arch/um/include/process.h +++ b/arch/um/include/process.h @@ -8,8 +8,8 @@ #include -extern void sig_handler(int sig, struct sigcontext sc); -extern void alarm_handler(int sig, struct sigcontext sc); +extern void sig_handler(int sig, struct sigcontext *sc); +extern void alarm_handler(int sig, struct sigcontext *sc); #endif diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c index 3f1694b..5aade60 100644 --- a/arch/um/os-Linux/signal.c +++ b/arch/um/os-Linux/signal.c @@ -12,6 +12,7 @@ #include "as-layout.h" #include "kern_util.h" #include "os.h" +#include "process.h" #include "sysdep/barrier.h" #include "sysdep/sigcontext.h" #include "user.h" diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c index e492805..bee98f4 100644 --- a/arch/um/os-Linux/time.c +++ b/arch/um/os-Linux/time.c @@ -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(const struct timeval *tv) 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 timespec *ts) { 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 timespec *ts) */ 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 timespec *ts) } #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); } -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/