1282814 – udev events are reordered relative to kernel uevents

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Bug 1282814 - udev events are reordered relative to kernel uevents

Summary: udev events are reordered relative to kernel uevents

Keywords:
Status:	CLOSED INSUFFICIENT_DATA
Alias:	None
Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	systemd
Sub Component:
Version:	7.2
Hardware:	Unspecified
OS:	Unspecified
Priority:	unspecified
Severity:	unspecified
Target Milestone:	rc
Target Release:	---
Assignee:	systemd-maint
QA Contact:	qe-baseos-daemons
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2015-11-17 14:10 UTC by Marius Vollmer
Modified:	2016-02-02 14:09 UTC (History)
CC List:	5 users (show)
Fixed In Version:
Doc Type:	Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed:	2016-02-02 14:09:57 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)
udevadm monitor (19.71 KB, text/plain) 2015-11-17 14:10 UTC, Marius Vollmer	no flags	Details
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Description Marius Vollmer 2015-11-17 14:10:47 UTC

Created attachment 1095496 [details]
udevadm monitor

Description of problem:

During the check-storage-mdraid test of Cockpit, a existing partition disappears from the knowledge of storaged.  A "udevadm trigger" or restart of storaged brings it back.

The reason seems to be that storaged receives a "remove" udev event for that partition and nothing after that.  The reason for _that_ seems to be that something reorders events so that a pair of "remove/add" kernel uevents arrives as a "add/remove" udev events at the application.

Attached is a "udev monitor" log for a run of check-storage-mdraid.  The test essentially 

 - creates a mdraid device
 - mucks around a bit with it
 - creates a gpt partition table on it with parted
 - creates a 20 MB partition on it with parted
 - creates a partition with parted that fills the rest of the device

At this point, storaged has received a "remove" event for the first partition.

Version-Release number of selected component (if applicable):
systemd-219-11.el7.x86_64

How reproducible:
Always with the exact images that I am using.  Very sporadically with other images.



Here is the interesting part of the log:

KERNEL[114.740468] change   /devices/virtual/block/md127 (block)
KERNEL[114.742033] add      /devices/virtual/block/md127/md127p1 (block)
UDEV  [114.745086] remove   /devices/virtual/block/md127/md127p1 (block)
KERNEL[114.762729] remove   /devices/virtual/block/md127/md127p1 (block)   <- kernel remove
KERNEL[114.762999] add      /devices/virtual/block/md127/md127p1 (block)   <- kernel add
KERNEL[114.763589] add      /devices/virtual/block/md127/md127p2 (block)
KERNEL[114.777821] change   /devices/virtual/block/md127 (block)
UDEV  [114.793438] change   /devices/virtual/block/md127 (block)
UDEV  [114.813974] add      /devices/virtual/block/md127/md127p1 (block)
UDEV  [114.819050] add      /devices/virtual/block/md127/md127p1 (block)   <- udev add
UDEV  [114.842078] remove   /devices/virtual/block/md127/md127p1 (block)   <- udev remove
UDEV  [114.849552] add      /devices/virtual/block/md127/md127p2 (block)
UDEV  [114.879320] change   /devices/virtual/block/md127 (block)
KERNEL[115.050059] change   /devices/virtual/block/md127/md127p2 (block)

Comment 2 Marius Vollmer 2015-11-18 10:00:44 UTC

As I found out later, the virtual machine had some unexpected CPU and I/O load on it while this was happening (mkdumprd was running).

Comment 3 Harald Hoyer 2015-12-14 15:17:21 UTC

Could you please run udevadm monitor with the "-p" flag, so that we can see the sequence numbers?

Comment 4 Marius Vollmer 2016-02-02 14:09:57 UTC

This has last happened on 27 Nov 2015, so I guess it has been fixed by some update or other.

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