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 cleans up the syscalls that are mainly used to control the
scheduling readiness of a thread. The different use cases and
requirements were somehow mixed together in the previous interface. The
new syscall set is:
1) pause_thread and resume_thread
They don't affect the state of the thread (IPC, signalling, etc.) but
merely decide wether the thread is allowed for scheduling or not, the
so-called pause state. The pause state is orthogonal to the thread state
and masks it when it comes to scheduling. In contrast to the stopped
state, which is described in "stop_thread and restart_thread", the
thread state and the UTCB content of a thread may change while in the
paused state. However, the register state of a thread doesn't change
while paused. The "pause" and "resume" syscalls are both core-restricted
and may target any thread. They are used as back end for the CPU session
calls "pause" and "resume". The "pause/resume" feature is made for
applications like the GDB monitor that transparently want to stop and
continue the execution of a thread no matter what state the thread is
in.
2) stop_thread and restart_thread
The stop syscall can only be used on a thread in the non-blocking
("active") thread state. The thread then switches to the "stopped"
thread state in wich it explicitely waits for a restart. The restart
syscall can only be used on a thread in the "stopped" or the "active"
thread state. The thread then switches back to the "active" thread state
and the syscall returns whether the thread was stopped. Both syscalls
are not core-restricted. "Stop" always targets the calling thread while
"restart" may target any thread in the same PD as the caller. Thread
state and UTCB content of a thread don't change while in the stopped
state. The "stop/restart" feature is used when an active thread wants to
wait for an event that is not known to the kernel. Actually the syscalls
are used when waiting for locks and on thread exit.
3) cancel_thread_blocking
Does cleanly cancel a cancelable blocking thread state (IPC, signalling,
stopped). The thread whose blocking was cancelled goes back to the
"active" thread state. It may receive a syscall return value that
reflects the cancellation. This syscall doesn't affect the pause state
of the thread which means that it may still not get scheduled. The
syscall is core-restricted and may target any thread.
4) yield_thread
Does its best that a thread is scheduled as few as possible in the
current scheduling super-period without touching the thread or pause
state. In the next superperiod, however, the thread is scheduled
"normal" again. The syscall is not core-restricted and always targets
the caller.
Fixes#2104
This patch establishes the sole use of generic headers across all
kernels. The common 'native_capability.h' is based on the version of
base-sel4. All traditional L4 kernels and Linux use the same
implementation of the capability-lifetime management. On base-hw, NOVA,
Fiasco.OC, and seL4, custom implementations (based on their original
mechanisms) are used, with the potential to unify them further in the
future.
This change achieves binary compatibility of dynamically linked programs
across all kernels.
Furthermore, the patch introduces a Native_capability::print method,
which allows the easy output of the kernel-specific capability
representation using the base/log.h API.
Issue #1993
This patch cleans up the thread API and comes with the following
noteworthy changes:
- Introduced Cpu_session::Weight type that replaces a formerly used
plain integer value to prevent the accidental mix-up of
arguments.
- The enum definition of Cpu_session::DEFAULT_WEIGHT moved to
Cpu_session::Weight::DEFAULT_WEIGHT
- New Thread constructor that takes a 'Env &' as first argument.
The original constructors are now marked as deprecated. For the
common use case where the default 'Weight' and 'Affinity' are
used, a shortcut is provided. In the long term, those two
constructors should be the only ones to remain.
- The former 'Thread<>' class template has been renamed to
'Thread_deprecated'.
- The former 'Thread_base' class is now called 'Thread'.
- The new 'name()' accessor returns the thread's name as 'Name'
object as centrally defined via 'Cpu_session::Name'. It is meant to
replace the old-fashioned 'name' method that takes a buffer and size
as arguments.
- Adaptation of the thread test to the new API
Issue #1954
This patch establishes a common organization of header files
internal to the base framework. The internal headers are located at
'<repository>/src/include/base/internal/'. This structure has been
choosen to make the nature of those headers immediately clear when
included:
#include <base/internal/lock_helper.h>
Issue #1832
