Package: linux-image-2.6.26-2-openvz-amd64 Version: 2.6.26-25lenny1 Severity: normal
On Lenny, I have observed the following behaviour: An I/O deadlock occurs under the following conditions: . OpenVZ container data stored on an LVM for which the PV is an md RAID1 . RAID1 md undergoing a rebuild or check . An LVM snapshot is active for the logical volume (in order to take a backup) . I/O occurs within the container The RAID resync then stops, as does all other I/O to the filesystem which is mounted upon the LVM. Adding various debug to the md raid1 driver shows that when the system gets to this state, there are a number of bio requests which are still pending (or at least their callback never gets executed). http://marc.info/?t=128473541100001&r=1&w=2 Adding the debug printks and atomic counters appears to make the deadlock occur more readily (within seconds rather than minutes of starting the openvz container). My guess was that this is some sort of a priority inversion deadlock, I/O in the container is triggering I/O outside of the container (via LVM snapshot) which must complete first (because of the OpenVZ scheduling rules or otherwise), and possibly the md barrier code is enforcing the opposite ordering. .. but when I tried: echo 0 > /sys/block/sda/queue/iosched/virt_mode echo 0 > /sys/block/sdb/queue/iosched/virt_mode prior to starting the container, didn't seem to change things. So maybe that's not the problem. Simply using the container private directory as a chroot, and placing reasonably heavy I/O load does not seem to cause the same deadlock to occur. I haven't seen the deadlock occur on 2.6.32, but haven't tried to insert the same debugging statements. -- System Information: Debian Release: squeeze/sid APT prefers testing APT policy: (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 2.6.32-5-openvz-amd64 (SMP w/8 CPU cores) Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968) Shell: /bin/sh linked to /bin/dash Versions of packages linux-image-2.6.26-2-openvz-amd64 depends on: ii debconf [debconf-2.0] 1.5.36 Debian configuration management sy ii initramfs-tools [linux-initra 0.98.5 tools for generating an initramfs ii module-init-tools 3.12-1 tools for managing Linux kernel mo ii vzctl 3.0.24-10 server virtualization solution - c linux-image-2.6.26-2-openvz-amd64 recommends no packages. Versions of packages linux-image-2.6.26-2-openvz-amd64 suggests: pn grub | lilo <none> (no description available) pn linux-doc-2.6.26 <none> (no description available) -- To UNSUBSCRIBE, email to debian-kernel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20101122131743.2836.76269.report...@ermintrude.seoss.co.uk
