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Message-ID: <504EE124.3010401@linaro.org>
Date: Tue, 11 Sep 2012 08:58:44 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: John Stultz <john.stultz@...aro.org>
CC: prarit@...hat.com, xen-devel@...ts.xensource.com,
linaro-dev@...ts.linaro.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-pm@...r.kernel.org, Frederic Weisbecker <fweisbec@...il.com>,
richardcochran@...il.com,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"Rafael J. Wysocki" <rjw@...k.pl>, linux-acpi@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>, mingo@...nel.org,
lenb@...nel.org
Subject: Re: CONFIG_NO_HZ + CONFIG_CPU_IDLE freeze the system (Was Re: [PATCH]
acpi : remove power from acpi_processor_cx structure)
On 09/11/2012 02:18 AM, John Stultz wrote:
> On 09/10/2012 12:45 PM, Daniel Lezcano wrote:
>> On 09/10/2012 07:14 PM, John Stultz wrote:
>>> In the meantime, I'll try to reproduce on my T61. If you could send me
>>> your .config, I'd appreciate it.
>> http://pastebin.com/qSxqfdDK
>>
>> The header of the config file shows for a v3.5-rc7 because it is the
>> result of the git-bisect. If you keep this config file for the latest
>> kernel that should reproduce the problem.
>>
>> Let me know if you were able to reproduce the problem.
> Great! With this I was able to quickly reproduce the problem and I think
> I have a fix.
Cool !
> Would you mind testing the following patch? It seems to resolve the
> issue, but I've not yet run it through my test suite to make sure it
> didn't break anything else.
No problem, I will try it this evening.
Is this problem related to all 32bits arch ?
Thanks !
-- Daniel
> If both your and my testing comes back ok, I'll submit it to Thomas.
>
> thanks
> -john
>
> From f10a285a5b532a14d3330f6e60e4d7bd5627932a Mon Sep 17 00:00:00 2001
> From: John Stultz <john.stultz@...aro.org>
> Date: Mon, 10 Sep 2012 20:00:15 -0400
> Subject: [PATCH] time: Fix timeekeping_get_ns overflow on 32bit systems
>
> Daniel Lezcano reported seeing multi-second stalls from
> keyboard input on his T61 laptop when NOHZ and CPU_IDLE
> were enabled on a 32bit kernel.
>
> He bisected the problem down to
> 1e75fa8be9fb61e1af46b5b3b176347a4c958ca1 (time: Condense
> timekeeper.xtime into xtime_sec).
>
> After reproducing this issue, I narrowed the problem down
> to the fact that timekeeping_get_ns() returns a 64bit
> nsec value that hasn't been accumulated. In some cases
> this value was being then stored in timespec.tv_nsec
> (which is a long).
>
> On 32bit systems, With idle times larger then 4 seconds
> (or less, depending on the value of xtime_nsec), the
> returned nsec value would overflow 32bits. This limited
> kept time from increasing, causing timers to not expire.
>
> The fix is to make sure we don't directly store the
> result of timekeeping_get_ns() into a tv_nsec field,
> instead using a 64bit nsec value which can then be
> added into the timespec via timespec_add_ns().
>
> With this patch I cannot reproduce the issue.
>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Richard Cochran <richardcochran@...il.com>
> Cc: Prarit Bhargava <prarit@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Reported-and-bisected-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
> kernel/time/timekeeping.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 34e5eac..d3b91e7 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -303,10 +303,11 @@ void getnstimeofday(struct timespec *ts)
> seq = read_seqbegin(&tk->lock);
>
> ts->tv_sec = tk->xtime_sec;
> - ts->tv_nsec = timekeeping_get_ns(tk);
> + nsecs = timekeeping_get_ns(tk);
>
> } while (read_seqretry(&tk->lock, seq));
>
> + ts->tv_nsec = 0;
> timespec_add_ns(ts, nsecs);
> }
> EXPORT_SYMBOL(getnstimeofday);
> @@ -345,6 +346,7 @@ void ktime_get_ts(struct timespec *ts)
> {
> struct timekeeper *tk = &timekeeper;
> struct timespec tomono;
> + s64 nsec;
> unsigned int seq;
>
> WARN_ON(timekeeping_suspended);
> @@ -352,13 +354,14 @@ void ktime_get_ts(struct timespec *ts)
> do {
> seq = read_seqbegin(&tk->lock);
> ts->tv_sec = tk->xtime_sec;
> - ts->tv_nsec = timekeeping_get_ns(tk);
> + nsec = timekeeping_get_ns(tk);
> tomono = tk->wall_to_monotonic;
>
> } while (read_seqretry(&tk->lock, seq));
>
> - set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
> - ts->tv_nsec + tomono.tv_nsec);
> + ts->tv_sec += tomono.tv_sec;
> + ts->tv_nsec = 0;
> + timespec_add_ns(ts, nsec + tomono.tv_nsec);
> }
> EXPORT_SYMBOL_GPL(ktime_get_ts);
>
> @@ -1244,6 +1247,7 @@ void get_monotonic_boottime(struct timespec *ts)
> {
> struct timekeeper *tk = &timekeeper;
> struct timespec tomono, sleep;
> + s64 nsec;
> unsigned int seq;
>
> WARN_ON(timekeeping_suspended);
> @@ -1251,14 +1255,15 @@ void get_monotonic_boottime(struct timespec *ts)
> do {
> seq = read_seqbegin(&tk->lock);
> ts->tv_sec = tk->xtime_sec;
> - ts->tv_nsec = timekeeping_get_ns(tk);
> + nsec = timekeeping_get_ns(tk);
> tomono = tk->wall_to_monotonic;
> sleep = tk->total_sleep_time;
>
> } while (read_seqretry(&tk->lock, seq));
>
> - set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
> - ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec);
> + ts->tv_sec += tomono.tv_sec + sleep.tv_sec;
> + ts->tv_nsec = 0;
> + timespec_add_ns(ts, nsec + tomono.tv_nsec + sleep.tv_nsec);
> }
> EXPORT_SYMBOL_GPL(get_monotonic_boottime);
>
--
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