Messages in this thread | | | Date | Sat, 3 Jan 2009 19:04:24 +0000 | From | "Duane Griffin" <> | Subject | Re: [PATCH] v2 Re: Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009 |
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2009/1/3 Chris Adams <cmadams@hiwaay.net>: > Once upon a time, Duane Griffin <duaneg@dghda.com> said: >> How about instead of a switch statement, assigning the message to a >> variable and printing that. I.e. something like: > > Good point. Here's an updated version that also adds a comment to the > xtime_lock definition about not using printk.
Good idea.
> -- > Chris Adams <cmadams@hiwaay.net> > Systems and Network Administrator - HiWAAY Internet Services > I don't speak for anybody but myself - that's enough trouble. > > > From: Chris Adams <cmadams@hiwaay.net> > > The code to handle leap seconds printks an information message when the > second is inserted or deleted. It does this while holding xtime_lock. > However, printk wakes up klogd, and in some cases, the scheduler tries > to get the current kernel time, trying to get xtime_lock (which results > in a deadlock). This moved the printks outside of the lock. It also > adds a comment to not use printk while holding xtime_lock. > > Signed-off-by: Chris Adams <cmadams@hiwaay.net> > --- > diff -urpN linux-2.6.28-git5-vanilla/include/linux/time.h linux-2.6.28-git5/include/linux/time.h > --- linux-2.6.28-git5-vanilla/include/linux/time.h 2009-01-02 22:09:10.000000000 -0600 > +++ linux-2.6.28-git5/include/linux/time.h 2009-01-03 11:57:27.000000000 -0600 > @@ -99,6 +99,12 @@ static inline struct timespec timespec_s > > extern struct timespec xtime; > extern struct timespec wall_to_monotonic; > + > +/* > + * Do not call printk while holding this lock; it wakes klogd and the > + * scheduler may try to get the current kernel time, which will try to get > + * this lock. > + */ > extern seqlock_t xtime_lock; > > extern unsigned long read_persistent_clock(void); > diff -urpN linux-2.6.28-git5-vanilla/kernel/time/ntp.c linux-2.6.28-git5/kernel/time/ntp.c > --- linux-2.6.28-git5-vanilla/kernel/time/ntp.c 2009-01-02 22:09:34.000000000 -0600 > +++ linux-2.6.28-git5/kernel/time/ntp.c 2009-01-03 11:57:46.000000000 -0600 > @@ -130,6 +130,7 @@ void ntp_clear(void) > static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) > { > enum hrtimer_restart res = HRTIMER_NORESTART; > + const char *msg = NULL; > > write_seqlock(&xtime_lock); > > @@ -140,8 +141,7 @@ static enum hrtimer_restart ntp_leap_sec > xtime.tv_sec--; > wall_to_monotonic.tv_sec++; > time_state = TIME_OOP; > - printk(KERN_NOTICE "Clock: " > - "inserting leap second 23:59:60 UTC\n"); > + msg = "Clock: inserting leap second 23:59:60 UTC"; > hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC); > res = HRTIMER_RESTART; > break; > @@ -150,8 +150,7 @@ static enum hrtimer_restart ntp_leap_sec > time_tai--; > wall_to_monotonic.tv_sec--; > time_state = TIME_WAIT; > - printk(KERN_NOTICE "Clock: " > - "deleting leap second 23:59:59 UTC\n"); > + msg = "Clock: deleting leap second 23:59:59 UTC"; > break; > case TIME_OOP: > time_tai++; > @@ -166,6 +165,9 @@ static enum hrtimer_restart ntp_leap_sec > > write_sequnlock(&xtime_lock); > > + if (msg) > + printk(KERN_NOTICE "%s\n", msg); > + > return res; > }
Looks good to me!
Cheers, Duane.
-- "I never could learn to drink that blood and call it wine" - Bob Dylan
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