udevd: convert to event worker processes

Event processes now get re-used after they handled an event. This reduces
pressure on the CPU significantly because cloned event processes no longer
cause page faults in the main daemon. After the events have settled, the
no longer needed worker processes get killed.

1 files changed, 12 insertions, 13 deletions

diff --git a/README b/README
index 773bc5508d..a14e5c0fcf 100644
--- a/README
+++ b/README
@@ -9,11 +9,13 @@ Important Note:
   recommend to replace a distro's udev installation with the upstream version.
 
 Requirements:
-  - Version 2.6.22 of the Linux kernel for reliable operation of this release of
-    udev. The kernel must not use the CONFIG_SYSFS_DEPRECATED* option.
+  - Version 2.6.25 of the Linux kernel with sysfs, procfs, signalfd, inotify,
+    unix domain sockets, networking and hotplug enabled.
 
-  - The kernel must have sysfs, unix domain sockets and networking enabled.
-    Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
+  - For reliable operation, the kernel must not use the CONFIG_SYSFS_DEPRECATED*
+    option.
+
+  - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
     supported.
 
   - The proc filesystem must be mounted on /proc/, the sysfs filesystem must
@@ -29,21 +31,18 @@ Operation:
   Udev creates and removes device nodes in /dev/, based on events the kernel
   sends out on device discovery or removal.
 
-  - Very early in the boot process, the /dev/ directory should get a 'tmpfs'
-    filesystem mounted, which is populated from scratch by udev. Created nodes
-    or changed permissions will not survive a reboot, which is intentional.
+  - Early in the boot process, the /dev/ directory should get a 'tmpfs'
+    filesystem mounted, which is maintained by udev. Created nodes or changed
+    permissions will not survive a reboot, which is intentional.
 
   - The content of /lib/udev/devices/ directory which contains the nodes,
     symlinks and directories, which are always expected to be in /dev, should
     be copied over to the tmpfs mounted /dev, to provide the required nodes
     to initialize udev and continue booting.
 
-  - The old hotplug helper /sbin/hotplug should be disabled on bootup, before
-    actions like loading kernel modules are taken, which may cause a lot of
-    events.
-
-  - The udevd daemon must be started on bootup to receive netlink uevents
-    from the kernel driver core.
+  - The old hotplug helper /sbin/hotplug should be disabled in the kernel
+    configuration, it is not needed, and may render the system unusable
+    because of a fork-bombing behavior.
 
   - All kernel events are matched against a set of specified rules in
     /lib/udev/rules.d/ which make it possible to hook into the event