** Description changed: [Impact] Software that relies on fine-grained pthread timeouts will spin indefinitely and drive up system load following a leap second, when the kernel's idea of time has become desynced and sub-1s timeouts are all hit immediately. Mysql and Java are in particular reported to be affected by this. This is a transient issue, in that it will go away the first time the system is rebooted after the leap second and is expected to be fixed before the next leap second occurs; nevertheless admins have been caught off-guard by this misbehavior and in some cases may not have noticed the problem or know what to do about it, so we should help them along by resetting the kernel clock with a minimal-risk base-files update. [Test Case] 1. Find a system that has been online, with mysqld or a java-based process running since before 2012-06-30. 2. Verify that one or more processes on the system are spinning in futex and driving up the system load. 3. Upgrade to the base-files package from -proposed. 4. Verify that the system load comes back down immediately. 5. A stress-test for leap-second handling has been provided at https://lkml.org/lkml/2012/7/3/37 [Regression potential] No analysis has been done on the effect of resetting the date on applications that require a high-accuracy clock. While this fixes the problem with the pthreads interfaces, it may cause other problems for other software. Since the proposed fix is to reset the kernel's date to the current date, which is not atomic, there will be a slight skew of the clock backwards in time. ntp *should* fix this shortly thereafter for machines that have it enabled. + Also, because there's a single version check for each copy of the SRU, users whose applications are negatively affected by the running of this date command will also be negatively affected on each subsequent upgrade of the system, up to and including the quantal devel release. As widely reported, the addition of the leap second on 2012-06-30 has caused high CPU usage and futex lockups in a lot of applications including JVMs, Mysql as well as desktop apps like Firefox and Thunderbird. https://lkml.org/lkml/2012/6/30/122 http://serverfault.com/questions/403732/anyone-else-experiencing-high-rates-of-linux-server-crashes-during-a-leap-second https://blog.mozilla.org/it/2012/06/30/mysql-and-the-leap-second-high-cpu-and-the-fix/ We've seen this ourselves on the Canonical infrastructure on both current Lucid and Precise kernels, i.e. ii linux-image-2.6.32-41-server 2.6.32-41.90 Linux kernel image for version 2.6.32 on x86_64 ii linux-image-3.2.0-24-generic 3.2.0-24.39 Linux kernel image for version 3.2.0 on 64 bit x86 SMP We can also confirm the 'date -s $(date)' workaround fixes the problem without requiring a reboot.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1020285 Title: Addition of leap second causes spuriously high CPU usage and futex lockups To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/base-files/+bug/1020285/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
