Re: Hang in work_resched

Peter Zijlstra
2008-01-31T08:55:38Z

On Wed, 2008-01-30 at 23:54 +0100, Guillaume Chazarain wrote:
> On Jan 29, 2008 11:30 PM, Guillaume Chazarain <guichaz@gmail.com> wrote:
> > =======================
> > gnome-termina S 00000027 0 2201 1
> > f6711fb0 00200082 cb330d62 00000027 f664105c 00000b1e 00000000 cb331880
> > 00000027 f660d780 009e3840 080ab7d8 080ab298 f6711000 c0103e7e 009e3840
> > 000e0002 00000002 080ab7d8 080ab298 bfb41be8 080ab7d8 0000007b c010007b
> > Call Trace:
> > [<c0103e7e>] work_resched+0x5/0x16
> > =======================
> >
> > This corresponds to the cli instruction:
> > c0103e7e: fa cli
>
> I bisected it, and the resulting commit is appended. Rerverting this
> commit applies cleanly on today's git
> (dd430ca20c40ecccd6954a7efd13d4398f507728) and makes the hang go away
> -:)

> commit 37bb6cb4097e29ffee970065b74499cbf10603a3

Does this patch from thomas fix it as well?

---

From: Thomas Gleixner <tglx@linutronix.de>

I justed walked trough the code, which updates xtime _AND_
wall_to_monotonic w/o updating xtime_cache:

There are a couple of places missing the xtime_cache update.

Signed-off-by: Thomas Gleixner <tglx@linuxtronix.de>
---
include/linux/time.h | 1 +
kernel/time.c | 1 +
kernel/time/timekeeping.c | 6 ++++--
3 files changed, 6 insertions(+), 2 deletions(-)

Index: linux-2.6/include/linux/time.h
===================================================================
--- linux-2.6.orig/include/linux/time.h
+++ linux-2.6/include/linux/time.h
@@ -122,6 +122,7 @@ extern void monotonic_to_bootbased(struc
extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_is_continuous(void);
extern void update_wall_time(void);
+extern void update_xtime_cache(u64 nsec);

/**
* timespec_to_ns - Convert timespec to nanoseconds
Index: linux-2.6/kernel/time.c
===================================================================
--- linux-2.6.orig/kernel/time.c
+++ linux-2.6/kernel/time.c
@@ -129,6 +129,7 @@ static inline void warp_clock(void)
write_seqlock_irq(&xtime_lock);
wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
xtime.tv_sec += sys_tz.tz_minuteswest * 60;
+ update_xtime_cache(0);
write_sequnlock_irq(&xtime_lock);
clock_was_set();
}
Index: linux-2.6/kernel/time/timekeeping.c
===================================================================
--- linux-2.6.orig/kernel/time/timekeeping.c
+++ linux-2.6/kernel/time/timekeeping.c
@@ -47,7 +47,7 @@ struct timespec wall_to_monotonic __attr
static unsigned long total_sleep_time; /* seconds */

static struct timespec xtime_cache __attribute__ ((aligned (16)));
-static inline void update_xtime_cache(u64 nsec)
+void update_xtime_cache(u64 nsec)
{
xtime_cache = xtime;
timespec_add_ns(&xtime_cache, nsec);
@@ -145,6 +145,7 @@ int do_settimeofday(struct timespec *tv)

set_normalized_timespec(&xtime, sec, nsec);
set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
+ update_xtime_cache(0);

clock->error = 0;
ntp_clear();
@@ -252,8 +253,8 @@ void __init timekeeping_init(void)
xtime.tv_nsec = 0;
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
+ update_xtime_cache(0);
total_sleep_time = 0;
-
write_sequnlock_irqrestore(&xtime_lock, flags);
}

@@ -290,6 +291,7 @@ static int timekeeping_resume(struct sys
}
/* Make sure that we have the correct xtime reference */
timespec_add_ns(&xtime, timekeeping_suspend_nsecs);
+ update_xtime_cache(0);
/* re-base the last cycle value */
clock->cycle_last = clocksource_read(clock);
clock->error = 0;