Rewrite kdump's udev rules
According to udev's man page, PROGRAM is either used to determine
device's name or whether the device matches the rule. So we should
use RUN insteand. Meanwhile, both RUN / PROGRAM only accepts very
short-running foreground tasks, but kdump restart may take a long
time if there are any device changes that will lead to image rebuild,
which may lead to buggy behavior.
On the other hand, memory / CPU hot plug should never trigger a
initramfs rebuild.
To solve this problem, we will use new introduced "kdumpctl reload"
instead, and use systemd-run to create a transient service unit for
the reload and run it in no-block mode, so udev won't be blocked by
anything.
We need to make systemd-run execute in non-blocking mode, and do not
synchronously wait for the operation to finish, because udev expect
the command line in RUN to be finished immediately, however, kdumpctl
reload may take 0.5-1s for an ordinary reload, or even slower on some
machines. So we give systemd-run an explicit --no-block option to run
in non-blocking mode. Without --no-blocking, systemd-run will verify,
enqueue and wait for the operation to finish. By using the --no-block
option, systemd-run will only verify and enqueue the unit then
return. In this way, we make sure the command is executed
asynchronously, and the status will be monitored and logged by
systemd, which is reliable and non-blocking.
Another thing to mention is that --no-block is only needed after
systemd-v220, before v220 systemd-run uses non-blocking mode by
default and --no-block option is not available on earlier systemd
versions.
Also reformat the udev rules to a more maintanceable format.
Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
2018-10-24 08:58:51 +00:00
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SUBSYSTEM=="cpu", ACTION=="add", GOTO="kdump_reload"
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SUBSYSTEM=="cpu", ACTION=="remove", GOTO="kdump_reload"
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SUBSYSTEM=="memory", ACTION=="online", GOTO="kdump_reload"
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SUBSYSTEM=="memory", ACTION=="offline", GOTO="kdump_reload"
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GOTO="kdump_reload_end"
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LABEL="kdump_reload"
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Make udev reload rules quiet during bootup
In commit 1c97aee and commit 227c185 udev rules was rewritten to use
systemd-run to run in a non-blocking mode. The problem is that it's a
bit noise, especially on machine bootup, systemd will always generate
extra logs for service start, you might see your journal full of lines
like these if you have many CPUs (each CPU generates a udev event on
boot):
...
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
...
While system is still booting up, kdump service is not started yet, so
systemd-run calls will end up doing nothing, the throttler being called
by systemd-run will just exit if kdump is not loaded.
This patch avoid systemd-run from being called at first place if kdump
service is not running by checking kdump.service status in udev rule,
so there won't be unnecessary logs.
Also remove the kdump service checking logic in kdump-udev-throttler as
udev is the only expected callee of this script, if it's not being
called at first place when kdump service is running, this checking will
be redundant. And even if any user called this script manually, it will
still work well as this script will call 'kdumpctl reload', it reload
the kdump resource only if kdump is loaded already.
Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
2018-11-22 14:56:08 +00:00
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# If kdump is not loaded, calling kdump-udev-throttle will end up
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# doing nothing, but systemd-run will always generate extra logs for
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# each call, so trigger the kdump-udev-throttler only if kdump
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# service is active to avoid unnecessary logs
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RUN+="/bin/sh -c '/usr/bin/systemctl is-active kdump.service || exit 0; /usr/bin/systemd-run --quiet --no-block /usr/lib/udev/kdump-udev-throttler'"
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Rewrite kdump's udev rules
According to udev's man page, PROGRAM is either used to determine
device's name or whether the device matches the rule. So we should
use RUN insteand. Meanwhile, both RUN / PROGRAM only accepts very
short-running foreground tasks, but kdump restart may take a long
time if there are any device changes that will lead to image rebuild,
which may lead to buggy behavior.
On the other hand, memory / CPU hot plug should never trigger a
initramfs rebuild.
To solve this problem, we will use new introduced "kdumpctl reload"
instead, and use systemd-run to create a transient service unit for
the reload and run it in no-block mode, so udev won't be blocked by
anything.
We need to make systemd-run execute in non-blocking mode, and do not
synchronously wait for the operation to finish, because udev expect
the command line in RUN to be finished immediately, however, kdumpctl
reload may take 0.5-1s for an ordinary reload, or even slower on some
machines. So we give systemd-run an explicit --no-block option to run
in non-blocking mode. Without --no-blocking, systemd-run will verify,
enqueue and wait for the operation to finish. By using the --no-block
option, systemd-run will only verify and enqueue the unit then
return. In this way, we make sure the command is executed
asynchronously, and the status will be monitored and logged by
systemd, which is reliable and non-blocking.
Another thing to mention is that --no-block is only needed after
systemd-v220, before v220 systemd-run uses non-blocking mode by
default and --no-block option is not available on earlier systemd
versions.
Also reformat the udev rules to a more maintanceable format.
Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
2018-10-24 08:58:51 +00:00
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LABEL="kdump_reload_end"
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