| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20090103180148.GA1375968@hiwaay.net>
Date: Sat, 3 Jan 2009 12:01:48 -0600
From: Chris Adams <cmadams@...aay.net>
To: Duane Griffin <duaneg@...da.com>
Cc: Linas Vepstas <linasvepstas@...il.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] v2 Re: Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009
Once upon a time, Duane Griffin <duaneg@...da.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.
--
Chris Adams <cmadams@...aay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.
From: Chris Adams <cmadams@...aay.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@...aay.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;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists