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We special-handle events with a TIMEOUT= set, so they don't get queued
or wait for parent events to finish, to make sure we can handle them
as fast as possible.
With this change we first try to find an idle worker process before
forking a new one.
It handles only RUN but not IMPORT and PROGRAM. There is no sane way
to suppress program execution. Most important programs run with IMPORT
these days. Also events can no longer suppressed with the libudev
netlink messages, so UDEV_RUN does nothing useful and is just
inconsistent.
There is no way to ignore an event these days. Libudev events can
not be suppressed. It only prevents RUN keys from being executed,
which results in an inconsistent behavior in current setups.
This should also address:
On Tue, Nov 3, 2009 at 16:21, Marco d'Itri <md@linux.it> wrote:
> udev_rules_new() in udev/udev-rules.c unconditionally creates the
> directory.
> This is a problem because the function is called also by e.g. udevadm
> test, and creating /dev/.udev/ when it does not exist is an unacceptable
> side effect which will break everything else that checks for its
> existence to know if udev is running.
On Wed, Oct 7, 2009 at 21:46, Alan Jenkins <sourcejedi.lkml@googlemail.com> wrote:
> Udev would have avoided the race prior to
>
> 82c785e "udevd: remove check for dev_t, DEVPATH_OLD takes care of that"
>
> (the "check" removed here used to serialize events based on the device
> major:minor number).
On Wed, Oct 7, 2009 at 22:31, Michael Guntsche <mike@it-loops.com> wrote:
> add /module/8250_pnp (module)
> remove /devices/platform/serial8250/tty/ttyS0 (tty)
> add /devices/pnp0/00:05/tty/ttyS0 (tty)
On Wed, Sep 23, 2009 at 23:11, Matthias Schwarzott <zzam@gentoo.org> wrote:
> It is about ioctl failures on amd64:
> http://bugs.gentoo.org/show_bug.cgi?id=286041
>
> A bad parameter type to an ioctl() call causes udev-146 to generate "error
> getting buffer for inotify" messages in syslog. The offending code is
> roughly:
>
> ssize_t nbytes, pos;
> // ...
> ioctl(fd, FIONREAD, &nbytes);
>
> where ssize_t is 64 bits on amd64, but the kernel code for FIONREAD (at least
> through gentoo-sources-2.6.31) uses type int:
>
> p = (void __user *) arg;
> switch (cmd) {
> case FIONREAD:
> // ...
> ret = put_user(send_len, (int __user *) p);
>
> so the upper 32 bits of "nbytes" are left uninitialized, and the subsequent
> malloc(nbytes) fails unless those 32 bits happen to be zero (or the system has
> a LOT of memory).
External programs triggered by events (via RUN=) will inherit udev's
signal mask, which is set to block all but SIGALRM. For most utilities,
this is OK, but if we start daemons from RUN=, we run into trouble
(especially as SIGCHLD is blocked).
This change saves the original sigmask when udev starts, and restores it
just before we exec() the external command.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
It did not work for the last couple of releases.
If RUN{record_failed}+="..." is given, a non-zero execution will mark
the event as failed. Recorded failed events can be re-triggered with:
udevadm trigger --type=failed
The failed tracking _might_ be useful for things which might not be
ready to be executed at early bootup, but a bit later when the needed
dependencies are available. In many cases though, it indicates that
something is used in a way it should not.
We may need to handle SIGCHLD before the queued worker message. The last
reference, from the SIGCHLD or the worker message will clean up the worker
context. In case we receive an unexpected SIGCHLD with an error, we let
the event fail and clean up the worker context.
Persistent network rules write out new rules files. When rules change,
we need to kill all workers to update the in-memory copy of the rules.
We need to make sure, that a worker finshes its work for all device
messages it has accepted, before it exits after a SIGTERM from the main
process.
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.
Directory lookups show up in profiling. The queue files are responsible
for a large proportion of file-related system calls in udev coldplug.
Instead of creating a file for each event, append their details to a
log file. The file is periodically rebuilt (garbage-collected) to
prevent it from growing indefinitely.
This single queue file replaces both the queue directory and the
uevent_seqnum file. On desktop systems the file tends not to grow
beyond one page. So it should also save a small amount of memory in
tmpfs.
Tests on a running EeePC indicate average savings of 5% *udevd* cpu time
as measured by oprofile. __link_path_walk is reduced from 1.5% to
1.3%. It is not completely clear where the rest of the gains come from.
In tests running ~400 events, the queue file is rebuilt about 5 times.
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Instead of of our own private monitor socket, we send the
processed event back to our netlink socket, to the multicast
group 2 -- so any number of users can listen to udev events,
just like they can listen to kernel emitted events on group 1.
There's still a slight race condition when using udevadm settle, if the
udev daemon has a pending inotify event but hasn't yet generated the
"change" uevent for it, the kernel and udev sequence numbers will match
and settle will exit.
Now udevadm settle will send a control message to udevd, which will
respond by sending SIGUSR1 back to the waiting udevadm settle once it
has completed the main loop iteration in which it received the control
message.
If there were no pending inotify events, this will simply wake up the
udev daemon and allow settle to continue. If there are pending inotify
events, they are handled first in the main loop so when settle is
continued they will have been turned into uevents and the kernel
sequence number will have been incremented.
Since the inotify event is pending for udevd when the close() system
call returns (it's queued as part of the kernel handling for that system
call), and since the kernel sequence number is incremented by writing to
the uevent file (as udevd does), this solves the race.
When the settle continues, if there were pending inotify events that
udevd had not read, they are now pending uevents which settle can wait
for.
Signed-off-by: Scott James Remnant <scott@ubuntu.com>
This allows you to re-process the rules if the content of the device
has been changed, most useful for block subsystem to cause vol_id to
be run again.
udevd's event_queue_manager loop is pretty sensitive to the
delays of exiting child processes. I found that it helps boot
times if we try to reap children as quickly as possible.
This patch changes event_queue_manager to call sigchilds_waiting
if it finds a signal has been received.
Signed-off-by: Olaf Kirch <okir@suse.de>
In certain cut-down situations such as an installer or inside the
initramfs, we simply don't have any kind of name service. While we
could use rules without OWNER or GROUP, it's better to have the same
rules as a full system and have udevd ignore those parts of the rules.
Adds a --resolve-names=never switch to udevd that has this effect.
udevd uses a rather old-fashioned way of handling signals
while waiting for input through select (ie by using an unnamed
pipe, to which the signal handler writes one byte for every signal
received). This is rather awkward and may potentially even block
if we receive more signals than the kernel's pipe buffer.
This patch replaces all of that with ppoll, which was designed
for this purpose.
It also removes the SA_RESTART flag from all installed signal
handlers, because otherwise the ppoll call would just be restarted
after handling eg a SIGCHLD.
Signed-off-by: Olaf Kirch <okir@suse.de>
This crops up in my threaded udevd profiles from time to time.
It's not consistent - probably due to variations in the number
of concurrent events - but it can hit 4% user time and higher.
The change halves the user time spent in compare_devpath().
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Unfortunately the linux rmdir implementation unhashes the dentry
even when the directory is not removed. This is apparently by
design (for filesystems that don't allow deleting open files).
Results from time(1) and oprofile follow.
Before:
0.35user 0.90system
samples % image name symbol name
608 9.6738 vmlinux shrink_dcache_parent
293 4.6619 vmlinux copy_page_c
271 4.3119 vmlinux copy_page_range
257 4.0891 udevd udev_rules_iter_next
After:
0.31user 0.67system
samples % image name symbol name
361 5.0419 vmlinux copy_page_range
322 4.4972 udevd udev_rules_iter_next
300 4.1899 vmlinux copy_page_c
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
"Hello world!" linked against libselinux parses /proc/mounts and
whatever else on startup, even when the lib is not needed at all.
Not funny! Get rid of that thing where it's not absolutely needed.
strerror() is not threadsafe. It uses a buffer to build messages of the form
"Unknown error 387689".
syslog() provides a %m format which is equivalent to strerror(errno).
As a GNU extension, this is also accepted by printf and friends.
At least in the current implementation, it is correctly threadsafe.
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
This was needed in the old days, where all the hotplug scripts did
nothing better than sleep for seconds to work around timing issues.
It made sure, that w continued to fork processes, while the machine
was doing nothing than sleeping, but the maximim number of childs
was already reached. This is no longer needed today, we do not run
many of these scripts anymore.
envp is not standardized, and may become invalid when environment variables
are modified. Since udev never actually uses it, we can simply remove it.
Should anyone miss it in future, they can use the standardized environ
variable - like udev_rules.c does already.
