This is a follow-up patch of "init: avoid too eager child restart". On
each config update of init, init re-applies child-specific configuration
changes. In the case of an already exited child, this re-evaluation
wrongly marked such a child as abandoned because the child's environment
sessions do no longer exist. Abandoning the child, in turn, triggers the
destruction and subseqent restart (because the <start> node of the
configuration still exists). The latter is bad for two reasons.
First, the exit state of the original instance becomes lost. Second, the
restart may have unexpected side effects due to sessions created by the
new instance. I.e., when resizing a partition in sculpt, init would
wrongly restart the gpt-write tool after the tool successfully exited.
This collides with a newly started instance of part_blk/resize2fs, which
now competes with the second gpt-write instance for the exclusive access
of the targeted block device.
The patch prevents init from re-applying configurations to exited
children. The accompanied test case covers the corner case.
This patch weakens the aggressive restart of a child with incomplete
environment sessions. The restart check is performed each time
the init configuration changes. In sculpt, this is not a rare special
case anymore but a frequent case when using the depot_rom as provider
for environment ROM sessions. In particular when starting a chain of
inter-depending children, the sculpt-manager quickly generates a
sequence of configurations with successively added start nodes.
While a child is abandoned, we must limit the start of anothers with
the same name. Otherwise - of the child has startup problems - a number
of abandoned children with the same name may queue up. This becomes a
problem whenever the child destruction depends on an asynchronous
service that provides an env session for the children. If the service is
unable to keep up with the session requests (both create and close),
the queue of abandoned children becomes unbounded. Limiting the child
creation rate to one abandoned child per name mitigates this problem.
This patch reduces the latency of state reports when children are
removed or added, thereby, accellerating the feedback loop between a
management component and init during the staged startup or removal of
inter-dependent components.
In contrast to most information of init's state reports, which can be
monitored at a relatively low rate (like 2 seconds in Sculpt's runtime),
resource requests call for an immediate response by the consumer of the
report. Otherwise the requesting child stays unnecessarily blocked until
the next rate-limited state report is due. This patch adds a fast lane
for such low-latency state updates to init.
When an environment session is provided by a async service such as a
sibling component, the session metadata must be preserved until end of
the lifetime of the session at the server has been acknowledged by the
server. Since the session meta data of env sessions are always part of
the 'Child' object, the destruction of this object must be deferred
until this point.
When exhausted of RAM quota while starting children, init used to throw
an uncaught 'Out_of_ram' exception as this condition was considered
fatal. However, this behavior is undesired when init is used in a highly
dynamic yet long-running fashion like sculpt's runtime subsystem. This
change keeps init running despite the error condition, giving the user
the chance to relieve the resource pressure.
The 'Buffered_xml' utility is used by three components and a fourth is
on the way. To avoid another duplication of the code, this patch makes
it publicly available at 'os/buffered_xml.h'.
With this patch, init responds to the exit of a child by closing all
sessions of the child. E.g., if a child is a GUI application, its
nitpicker session is closed at the time of exit, not at the time when
the start node disappears from init's configuration.
Since this change requires a modification of the 'Genode::Child' class,
it takes the chance to make the child-destruction less brutal. The
new version ensures that all threads of the destructed subsystem are
destructed before other sessions, in particular PD sessions. This
eliminates spurious page-fault warnings during the child destruction.
On Fiasco.OC, closing the CPU session of a thread while being called by
the thread causes a deadlock. Hence, we skip the eager destruction of
CPU sessions on this kernel.
Related to issue #2659
The patch adjust the code of the base, base-<kernel>, and os repository.
To adapt existing components to fix violations of the best practices
suggested by "Effective C++" as reported by the -Weffc++ compiler
argument. The changes follow the patterns outlined below:
* A class with virtual functions can no longer publicly inherit base
classed without a vtable. The inherited object may either be moved
to a member variable, or inherited privately. The latter would be
used for classes that inherit 'List::Element' or 'Avl_node'. In order
to enable the 'List' and 'Avl_tree' to access the meta data, the
'List' must become a friend.
* Instead of adding a virtual destructor to abstract base classes,
we inherit the new 'Interface' class, which contains a virtual
destructor. This way, single-line abstract base classes can stay
as compact as they are now. The 'Interface' utility resides in
base/include/util/interface.h.
* With the new warnings enabled, all member variables must be explicitly
initialized. Basic types may be initialized with '='. All other types
are initialized with braces '{ ... }' or as class initializers. If
basic types and non-basic types appear in a row, it is nice to only
use the brace syntax (also for basic types) and align the braces.
* If a class contains pointers as members, it must now also provide a
copy constructor and assignment operator. In the most cases, one
would make them private, effectively disallowing the objects to be
copied. Unfortunately, this warning cannot be fixed be inheriting
our existing 'Noncopyable' class (the compiler fails to detect that
the inheriting class cannot be copied and still gives the error).
For now, we have to manually add declarations for both the copy
constructor and assignment operator as private class members. Those
declarations should be prepended with a comment like this:
/*
* Noncopyable
*/
Thread(Thread const &);
Thread &operator = (Thread const &);
In the future, we should revisit these places and try to replace
the pointers with references. In the presence of at least one
reference member, the compiler would no longer implicitly generate
a copy constructor. So we could remove the manual declaration.
Issue #465
This patch makes service-announce messages depend on the configured
verbosity. It also omits "parent provides" title messages if no new
parent services are added during a config update.
The run tool now by default checks configurations with target-specific
XML schemata. Each component may define a config schema file in its
target.mk via the CONFIG_XSD variable. When the run tool has checked an
configuration of an init instance, it additionally goes through the
start nodes of the config. For each start node it checks whether there
is an XSD file that matches. If so, the run tool also checks the config
of the start node (if existant). This is done recursively. I.e., also
the child configs of a sub-init of a sub-init of the top-level init
receive a config check.
Issue #2600
This patch supplements init's service-forwarding mechanism to propagate
the insufficient RAM/cap quota conditions from the server to the client.
Without it, the client's session request stays pending infinitely.
This is a follow-up patch to "init: periodic state updates if sensible".
In situations where the report rate is deliberately limited via the
'delay_ms' attribute while also reporting child-resource stats, we don't
want generate reports at a fixed rate of one second. This patch limits
the rate according to the 'delay_ms' value.
Whenever a childs is terminated the exit value is propagate through a
new state report. Thereby it becomes possibly for a managing component
to react upon the terminating condition of a child.
Issue #2558.
Under certain circumstances we don't want inits state report to become too
outdated even if there is no change to its config or the sessions of its
children. This is the case if init is requested to provide a capability or RAM
info of it's children via its state report. Now, init automatically updates
the state report with each 1000 ms if the attribute 'child_caps' or
'child_ram' is positively set in the 'report' tag.
This patch propages the 'Service_denied' condition of forwarded sessions
to the parent. Without it, the invalid session request stays pending
infinitely, which leads to the problem described in issue #2542. It
turns out that suggested solution given in the issue text is actually
not needed when applying this fix.
Fixes#2542
This patch changes init's service forwarding such that pending requests
are kept unanswered as long as the requested service is not present
(yet). In dynamic-init scenarios, this is needed in situtions where the
dynamic init is known to eventually provide the service but the internal
subsystem is not ready yet. Previously, a client that attempted to
request a session in this early phase would get a 'Service_denied'
exception. By deferring the forwarding in this situation, the behaviour
becomes deterministic.
If a matching '<service>' exists but there is no matching policy sub
node, the request is answered with 'Service_denied' - as expected.
If a child is allowed to constrain physical memory allocations but left
the 'phys_start' and 'phys_size' session arguments blank, init applies
builtin constraints for allocating DMA buffers.
The only component that makes use of the physical-memory constraint
feature is the platform driver. Since the built-in heuristics are
applied to the platform driver's environment RAM session, all
allocations performed by the platform driver satisfy the DMA
constraints.
To justify building-in these heuristics into init as opposed to
supplying the values as configuration arguments, the values differ
between 32 and 64 bit. The configuration approach would raise the need
to differentiate init configurations for both cases, which are
completely identical otherwise.
Issue #2407
This patch reduces the number of exception types by facilitating
globally defined exceptions for common usage patterns shared by most
services. In particular, RPC functions that demand a session-resource
upgrade not longer reflect this condition via a session-specific
exception but via the 'Out_of_ram' or 'Out_of_caps' types.
Furthermore, the 'Parent::Service_denied', 'Parent::Unavailable',
'Root::Invalid_args', 'Root::Unavailable', 'Service::Invalid_args',
'Service::Unavailable', and 'Local_service::Factory::Denied' types have
been replaced by the single 'Service_denied' exception type defined in
'session/session.h'.
This consolidation eases the error handling (there are fewer exceptions
to handle), alleviates the need to convert exceptions along the
session-creation call chain, and avoids possible aliasing problems
(catching the wrong type with the same name but living in a different
scope).
This patch mirrors the accounting and trading scheme that Genode employs
for physical memory to the accounting of capability allocations.
Capability quotas must now be explicitly assigned to subsystems by
specifying a 'caps=<amount>' attribute to init's start nodes.
Analogously to RAM quotas, cap quotas can be traded between clients and
servers as part of the session protocol. The capability budget of each
component is maintained by the component's corresponding PD session at
core.
At the current stage, the accounting is applied to RPC capabilities,
signal-context capabilities, and dataspace capabilities. Capabilities
that are dynamically allocated via core's CPU and TRACE service are not
yet covered. Also, the capabilities allocated by resource multiplexers
outside of core (like nitpicker) must be accounted by the respective
servers, which is not covered yet.
If a component runs out of capabilities, core's PD service prints a
warning to the log. To observe the consumption of capabilities per
component in detail, the PD service is equipped with a diagnostic
mode, which can be enabled via the 'diag' attribute in the target
node of init's routing rules. E.g., the following route enables the
diagnostic mode for the PD session of the "timer" component:
<default-route>
<service name="PD" unscoped_label="timer">
<parent diag="yes"/>
</service>
...
</default-route>
For subsystems based on a sub-init instance, init can be configured
to report the capability-quota information of its subsystems by
adding the attribute 'child_caps="yes"' to init's '<report>'
config node. Init's own capability quota can be reported by adding
the attribute 'init_caps="yes"'.
Fixes#2398
This patch reworks the implementation of core's RAM service to make use
of the 'Session_object' and to remove the distinction between the
"metadata" quota and the managed RAM quota. With the new implementation,
the session implicitly allocates its metadata from its own account. So
there is not need to handle 'Out_of_metadata' and 'Quota_exceeded' via
different exceptions. Instead, the new version solely uses the
'Out_of_ram' exception.
Furthermore, the 'Allocator::Out_of_memory' exception has become an alias
for 'Out_of_ram', which simplifies the error handling.
Issue #2398
The 'diag' flag can be defined by a target node of a route in init's
configuration. It is propagated as session argument to the server, which
may evaluate the flag to enable diagnostic output for the corresponding
session.
Issue #2398
This patch makes use of the new 'Quota_transfer::Account' by the service
types in base/service.h and uses 'Quota_transfer' objects in
base/child.cc and init/server.cc.
Furthermore, it decouples the notion of an 'Async_service' from
'Child_service'. Init's 'Routed_service' is no longer a 'Child_service'
but is based on the new 'Async_service' instead.
With this patch in place, quota transfers do no longer implicitly use
'Ram_session_client' objects. So transfers can in principle originate
from component-local 'Ram_session_component' objects, e.g., as used by
noux. Therefore, this patch removes a strumbling block for turning noux
into a single threaded component in the future.
Issue #2398
This patch replaces the 'Parent::Quota_exceeded',
'Service::Quota_exceeded', and 'Root::Quota_exceeded' exceptions
by the single 'Insufficient_ram_quota' exception type.
Furthermore, the 'Parent' interface distinguished now between
'Out_of_ram' (the child's RAM is exhausted) from
'Insufficient_ram_quota' (the child's RAM donation does not suffice to
establish the session).
This eliminates ambiguities and removes the need to convert exception
types along the path of the session creation.
Issue #2398
This patch replaces the former use of size_t with the use of the
'Ram_quota' type to improve type safety (in particular to avoid
accidentally mixing up RAM quotas with cap quotas).
Issue #2398
This patch augments the existing session/session.h with useful types for
the session creation:
* The new 'Insufficient_ram_quota' and 'Insufficient_cap_quota'
exceptions are meant to supersede the old 'Quota_exceeded' exception
of the 'Parent' and 'Root' interfaces.
* The 'Session::Resources' struct subsumes the information about the
session quota provided by the client.
* The boolean 'Session::Diag' type will allow sessions to operate in a
diagnostic mode.
* The existing 'Session_label' is not also available under the alias
'Session::Label'.
* A few helper functions ease the extraction of typed session arguments
from the session-argument string.
Issue #2398
Init's service forwarding functionality did not take the service type
into account when forwarding a session request. If a server provides
multiple services, e.g. fb_sdl that provides both "Input" and
"Framebuffer", the type of the forwarded session request did not always
correspond to the actually requested type.
This patch equips init with the ability to act as a server that forwards
session requests to its children. Session requests can be routed
depending of the requested service type and the session label
originating from init's parent.
The feature is configured by one or multiple <service> nodes hosted in
init's <config> node. The routing policy is selected by via the regular
server-side policy-selection mechanism, for example:
<config>
...
<service name="LOG">
<policy label="noux">
<child name="terminal_log" label="important"/>
</policy>
<default-policy> <child name="nitlog"/> </default-policy>
</service>
...
</config>
Each policy node must have a <child> sub node, which denotes name of the
server with the 'name' attribute. The optional 'label' attribute defines
the session label presented to the server, analogous to how the
rewriting of session labels works in session routes. If not specified,
the client-provided label is presented to the server as is.
Fixes#2247
This patch removes the formerly built-in policy of responding to
resource requests with handing out slack quota. Instead, resource
requests have to be answered by an update of the init configuration with
adjusted quota values.
Note that this patch may break run scripts that depend on init's
original policy. Those run scripts may be adjusted by increasing the
quota for the components that use to inflate their RAM usage during
runtime such that the specified quota suffices for the entire lifetime
of the component.
This patch improves init's dynamic reconfigurability with respect to
adjustments of the RAM quota assigned to the children.
If the RAM quota is decreased, init withdraws as much quota from the
child's RAM session as possible. If the child's RAM session does not
have enough available quota, a resource-yield request is issued to
the child. Cooparative children may respond to such a request by
releasing memory.
If the RAM quota is increased, the child's RAM session is upgraded.
If the configuration exceeds init's available RAM, init re-attempts
the upgrade whenever new slack memory becomes available (e.g., by
disappearing other children).
This patch improves the accuracy of init's quota-saturation feature
(handing out all slack quota to a child by specifying an overly high RAM
quota for the child) and makes the RAM preserved by init configurable.
The preservation is specified as follows:
! <config>
! ...
! <resource name="RAM" preserve="1M"/>
! ...
! </config>
If not specified, init has a reasonable default of 160K (on 32 bit) and
320K (on 64 bit).
