are places where the "main thread" of the booting kernel (either the
thread which later becomes swapper or the thread which later becomes
init) has to stop and wait for action to take place in another thread
before continuing.
There are currently three such holds:
1. The intr_config_hooks SYSINIT waits for hooks registered via the
config_intrhook_establish function; this allows (typically) devices
which need interrupts enabled to complete their initialization to do
so before root is mounted.
2. The g_waitidle function waits for the GEOM event queue to be empty;
this ensures that all of the disks which have been attached have been
tasted before we attempt to mount root.
3. The vfs_mountroot_wait function (in addition to calling g_waitidle)
waits for holds registered via root_mount_hold; among other things, this
is used by the USB subsystem to ensure that we don't fail to mount root
if it's located on a USB disk which takes a while to probe.
Mainly focus on files that use BSD 3-Clause license.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
it automatically after it runs.
The config_intrhook mechanism allows a driver to stall the boot process
until device(s) required for booting are available, by not allowing system
inits to proceed until all intrhook functions have been unregistered.
Virtually all existing code simply unregisters from within the hook function
when it gets called.
This new function makes that common usage more convenient. Instead of
allocating and filling in a struct, passing it to a function that might (in
theory) fail, and checking the return code, now a driver can simply call
this cannot-fail routine, passing just the intrhook function and its arg.
Differential Revision: https://reviews.freebsd.org/D11963
Interrupt driven configuration hooks serve two purposes: they are a
mechanism for registering for a callback that is invoked once interrupt
services are available, and they hold off root device selection so long
as any configuration hooks are still active. Before this change, it was
not possible to safely register additional hooks from the context of a
configuration hook callback. The need for this feature arises when
interrupts are required to discover new devices (e.g. access to the XenStore
to find para-virtualized devices) which in turn also require the ability
to hold off root device selection until some lengthy, interrupt driven,
configuration task has completed (e.g. Xen front/back device driver
negotiation).
More specifically, the mutex protecting the list of active configuration
hooks is never held during a callback, and static information is used
to ensure proper ordering and only a single callback to each hook even
when faced with registration or removal of a hook during an active run.
Sponsored by: Spectra Logic Corporation
MFC after: 1 week.
interrupt-driven configuration handlers to complete, print out a
diagnostic message every 60 second indicating which handlers are
still running. Do this at most 5 times per run so as to avoid
scrolling out any useful information from the kernel message
buffer.
The interval of 60 seconds was selected based on a best guess as
to the nature of "long enough" and may want to be tuned higher
or lower depending on real-world tolerances.
MFC after: 3 days
Discussed with: scottl
for completion in run_interrupt_driven_config_hooks(). This is
helpful when trying to figure out which device drivers have gone
into la-la land during boot-time autoconfiguration.
MFC after: 3 days
after each SYSINIT() macro invocation. This makes a number of
lightweight C parsers much happier with the FreeBSD kernel
source, including cflow's prcc and lxr.
MFC after: 1 month
Discussed with: imp, rink
that the only remove hook operation that can occur while processing the
hooks is to remove the currently executing hook. This should be safe as
the existing code has assumed this already for a long time now.
Reviewed by: scottl
MFC after: 1 week
- Move intrhook stuff into kernel.h
- Remove all occurrences of #device <device.h>
- Add kernel.h were necessary (nowhere)
- delete device.h
This file contained the structures for cfdata (old style config) and is no
longer used. It was included by most drivers.
It confuses the remote debugger as the definition of 'struct device' in
device.h is found before the one in bus_private.h.
for possible buffer overflow problems. Replaced most sprintf()'s
with snprintf(); for others cases, added terminating NUL bytes where
appropriate, replaced constants like "16" with sizeof(), etc.
These changes include several bug fixes, but most changes are for
maintainability's sake. Any instance where it wasn't "immediately
obvious" that a buffer overflow could not occur was made safer.
Reviewed by: Bruce Evans <bde@zeta.org.au>
Reviewed by: Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by: Mike Spengler <mks@networkcs.com>
Add support for "interrupt driven configuration hooks".
A component of the kernel can register a hook, most likely
during auto-configuration, and receive a callback once
interrupt services are available. This callback will occur before
the root and dump devices are configured, so the configuration
task can affect the selection of those two devices or complete
any tasks that need to be performed prior to launching init.
System boot is posponed so long as a hook is registered. The
hook owner is responsible for removing the hook once their task
is complete or the system boot can continue.
kern_acct.c kern_clock.c kern_exit.c kern_synch.c kern_time.c:
Change the interface and implementation for the kernel callout
service. The new implemntaion is based on the work of
Adam M. Costello and George Varghese, published in a technical
report entitled "Redesigning the BSD Callout and Timer Facilities".
The interface used in FreeBSD is a little different than the one
outlined in the paper. The new function prototypes are:
struct callout_handle timeout(void (*func)(void *),
void *arg, int ticks);
void untimeout(void (*func)(void *), void *arg,
struct callout_handle handle);
If a client wishes to remove a timeout, it must store the
callout_handle returned by timeout and pass it to untimeout.
The new implementation gives 0(1) insert and removal of callouts
making this interface scale well even for applications that
keep 100s of callouts outstanding.
See the updated timeout.9 man page for more details.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
