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If a 'change' event is supposed to remove created symlinks, we create a new device structure from the sysfs device and fill it with the list of links, to compute the delta of the old and new list of links to apply. If the device is already 'remove'd by the kernel though, udev fails to create the device structure, so the links are not removed properly. > From: Neil Brown <nfbrown@suse.com> > Date: Thu, 8 Nov 2012 10:39:06 +0100 > Subject: [PATCH] If a 'change' event does not get handled by udev until > after the device has subsequently disappeared, udev mis-handles > it. This can happen with 'md' devices which emit a change > event and then a remove event when they are stopped. It is > normally only noticed if udev is very busy (lots of arrays > being stopped at once) or the machine is otherwise loaded > and reponding slowly. > > There are two problems. > > 1/ udev_device_new_from_syspath() will refuse to create the device > structure if the device does not exist in /sys, and particularly if > the uevent file does not exist. > If a 'db' file does exist, that is sufficient evidence that the device > is genuine and should be created. Equally if we have just received an > event from the kernel about the device, it must be real. > > This patch just disabled the test for the 'uevent' file, it doesn't > try imposing any other tests - it isn't clear that they are really > needed. > > 2/ udev_event_execute_rules() calls udev_device_read_db() on a 'device' > structure that is largely uninitialised and in particular does not > have the 'subsystem' set. udev_device_read_db() needs the subsystem > so it tries to read the 'subsystem' symlink out of sysfs. If the > device is already deleted, this naturally fails. > udev_event_execute_rules() knows the subsystem (as it was in the > event message) so this patch simply sets the subsystem for the device > structure to be loaded to match the subsystem of the device structure > that is handling the event. > > With these two changes, deleted handling of change events will still > correctly remove any symlinks that are not needed any more. Use udev_device_new() instead of allowing udev_device_new_from_syspath() to proceed without a sysfs device. |
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keymaps-force-release | ||
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man | ||
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TODO |
systemd System and Service Manager DETAILS: http://0pointer.de/blog/projects/systemd.html WEB SITE: http://www.freedesktop.org/wiki/Software/systemd GIT: git://anongit.freedesktop.org/systemd/systemd ssh://git.freedesktop.org/git/systemd/systemd GITWEB: http://cgit.freedesktop.org/systemd/systemd MAILING LIST: http://lists.freedesktop.org/mailman/listinfo/systemd-devel http://lists.freedesktop.org/mailman/listinfo/systemd-commits IRC: #systemd on irc.freenode.org BUG REPORTS: https://bugs.freedesktop.org/enter_bug.cgi?product=systemd AUTHOR: Lennart Poettering Kay Sievers ...and many others LICENSE: LGPLv2.1+ for all code - except sd-daemon.[ch] and sd-readahead.[ch] which are MIT - except src/udev/ which is GPLv2.0+ REQUIREMENTS: Linux kernel >= 2.6.39 with devtmpfs with cgroups (but it's OK to disable all controllers) optional but strongly recommended: autofs4, ipv6 dbus >= 1.4.0 libcap libblkid >= 2.20 (from util-linux) libkmod >= 5 PAM >= 1.1.2 (optional) libcryptsetup (optional) libgcrypt (optional) libaudit (optional) libacl (optional) libattr (optional) libselinux (optional) liblzma (optional) tcpwrappers (optional) libgcrypt (optional) libqrencode (optional) libmicrohttpd (optional) When you build from git you need the following additional dependencies: docbook-xsl xsltproc automake autoconf libtool intltool gperf gtkdocize (optional) python (optional) make, gcc, and similar tools During runtime you need the following dependencies: util-linux > v2.18 (requires fsck -l, agetty -s) sulogin (from sysvinit-tools, optional but recommended) dracut (optional) When systemd-hostnamed is used it is strongly recommended to install nss-myhostname to ensure that in a world of dynamically changing hostnames the hostname stays resolvable under all circumstances. In fact, systemd-hostnamed will warn if nss-myhostname is not installed. Packagers are encouraged to add a dependency on nss-myhostname to the package that includes systemd-hostnamed. Note that D-Bus can link against libsystemd-login.so, which results in a cyclic build dependency. To accommodate for this please build D-Bus without systemd first, then build systemd, then rebuild D-Bus with systemd support. WARNINGS: systemd will warn you during boot if /etc/mtab is not a symlink to /proc/mounts. Please ensure that /etc/mtab is a proper symlink. systemd will warn you during boot if /usr is on a different file system than /. While in systemd itself very little will break if /usr is on a separate partition many of its dependencies very likely will break sooner or later in one form or another. For example udev rules tend to refer to binaries in /usr, binaries that link to libraries in /usr or binaries that refer to data files in /usr. Since these breakages are not always directly visible systemd will warn about this, since this kind of file system setup is not really supported anymore by the basic set of Linux OS components. For more information on this issue consult http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken To run systemd under valgrind, compile with VALGRIND defined (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise, false positives will be triggered by code which violates some rules but is actually safe. ENGINEERING AND CONSULTING SERVICES: ProFUSION <http://profusion.mobi> offers professional engineering and consulting services for systemd for embedded and other use. Please contact Gustavo Barbieri <barbieri@profusion.mobi> for more information. Disclaimer: This notice is not a recommendation or official endorsement. However, ProFUSION's upstream work has been very beneficial for the systemd project.