| Commit message (Collapse) | Author | Age | Files | Lines |
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The embedded brains GmbH & Co. KG is the legal successor of embedded
brains GmbH.
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The goto label was directly after the loop, so we can replace the goto
with a break.
Close #4847.
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Updates #3053.
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Process ask for help requests on the current processor. This avoids
using inter-processor interrupts to make the system behaviour a bit more
predictable.
Update #4531.
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This patch set replaces the CPU budget algorithm enumeration with a set of CPU
budget operations which implement a particular CPU budget algorithm. This
helps to hide the CPU budget algorithm implementation details from the general
thread handling. The CPU budget callouts are turned into CPU budget
operations. This slightly reduces the size of the thread control block.
All schedulers used the default scheduler tick implementation. The tick
scheduler operation is removed and the CPU budget operations are directly used
in _Watchdog_Tick() if the executing thread uses a CPU budget algorithm. This
is performance improvement for all threads which do not use a CPU budget
algorithm (default behaviour).
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The _Thread_Dispatch() function was customized over time and now the
work is done by _Thread_Do_dispatch() and specialized wrappers. The
plain _Thread_Dispatch() is now only used in some CPU ports. Move it to
a separate file to avoid dead code in the general.
Change license to BSD-2-Clause according to file history and
re-licensing agreement.
Update #3053.
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The __builtin_unreachable() cannot be used with current GCC versions to
tell the compiler that a function does not return to the caller, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99151
Add a no return variant of _Thread_Dispatch_direct() to avoid generation
of dead code.
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Require that the corresponding lock is acquired before the action
handler returns. This helps to avoid recursion in the signal
processing.
Update #4244.
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Use common phrases for the file brief descriptions.
Update #3706.
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This order change fixes the Latex documentation build via Doxygen.
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Use the following variant which was already used by most source files:
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
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In uniprocessor and SMP configurations, the context switch extensions
were called during _Thread_Do_dispatch():
void _Thread_Do_dispatch( Per_CPU_Control *cpu_self, ISR_Level level )
{
Thread_Control *executing;
executing = cpu_self->executing;
...
do {
Thread_Control *heir;
heir = _Thread_Get_heir_and_make_it_executing( cpu_self );
...
_User_extensions_Thread_switch( executing, heir );
...
_Context_Switch( &executing->Registers, &heir->Registers );
...
} while ( cpu_self->dispatch_necessary );
...
}
In uniprocessor configurations, this is fine and the context switch
extensions are called for all thread switches except the very first
thread switch to the initialization thread. However, in SMP
configurations, the context switch may be invalidated and updated in the
low-level _Context_Switch() routine. See:
https://docs.rtems.org/branches/master/c-user/symmetric_multiprocessing_services.html#thread-dispatch-details
In case such an update happens, a thread will execute on the processor
which was not seen in the previous call of the context switch
extensions. This can confuse for example event record consumers which
use events generated by a context switch extension.
Fixing this is not straight forward. The context switch extensions call
must move after the low-level context switch. The problem here is that
we may end up in _Thread_Handler(). Adding the context switch
extensions call to _Thread_Handler() covers now also the thread switch
to the initialization thread. We also have to save the last executing
thread (ancestor) of the processor. Registers or the stack cannot be
used for this purpose. We have to add it to the per-processor
information. Existing extensions may be affected, since now context
switch extensions use the stack of the heir thread. The stack checker
is affected by this.
Calling the thread switch extensions in the low-level context switch is
difficult since at this point an intermediate stack is used which is
only large enough to enable servicing of interrupts.
Update #3885.
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Test for the proper system condition instead of using the
rtems_configuration_is_smp_enabled() workaround.
Update #3876.
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The use of a hand crafted lock for Per_CPU_Control::Lock was necessary
at some point in the SMP support development, but it is no longer
justified.
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Update #3706
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In case the robust thread dispatch is enabled by the CPU port, then the
interrupt level must not be changed through the task mode.
Update #3000.
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Add support to temporarily pin a thread to its current processor. This
may be used to access per-processor data structures in critical sections
with enabled thread dispatching, e.g. a pinned thread is allowed to
block.
Update #3508.
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This function is slighly too complex for inlining with two if
statements. The caller already needs a stack frame due to the potential
call to _Thread_Do_dispatch(). In _Thread_Dispatch_enable() the call to
_Thread_Do_dispatch() can be optimized to a tail call.
A text size comparision
(text size after patch - text size before patch)
/ text size before patch
on sparc/erc32 with SMP enabled showed these results:
Minimum -0.000697892 (fsdosfsname01.exe)
Median -0.00745021 (psxtimes01.exe)
Maximum -0.0233032 (spscheduler01.exe)
A text size comparision
text size after patch - text size before patch
on sparc/erc32 with SMP enabled showed these results:
Minimum -3312 (ada_sp09.exe)
Median -1024 (tm15.exe)
Maximum -592 (spglobalcon01.exe)
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Update #3060.
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This task variable is superfluous since we use thread-local storage now.
Update #2289.
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Move _Thread_Scheduler_ask_for_help(), rename it to
_Thread_Ask_for_help() and make it static.
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The fatal is internal indicator is redundant since the fatal source and
error code uniquely identify a fatal error. Keep the fatal user
extension is internal parameter for backward compatibility and set it to
false always.
Update #2825.
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On SMP configurations, it is a fatal error to call blocking operating
system with interrupts disabled, since this prevents delivery of
inter-processor interrupts. This could lead to executing threads which
are not allowed to execute resulting in undefined behaviour.
The ARM Cortex-M port has a similar problem, since the interrupt state
is not a part of the thread context.
Update #2811.
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Use a processor-specific interrupt frame during context switches in case
the executing thread is longer executes on the processor and the heir
thread is about to start execution. During this period we must not use
a thread stack for interrupt processing.
Update #2809.
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This function is useful for operations which synchronously block, e.g.
self restart, self deletion, yield, sleep. It helps to detect if these
operations are called in the wrong context. Since the thread dispatch
necessary indicator is not used, this is more robust in some SMP
situations.
Update #2751.
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Update #2556.
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This information turned out to be useless in the last couple of months.
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Rename _ISR_Disable() into _ISR_Local_disable(). Rename _ISR_Enable()
into _ISR_Local_enable(). Remove _Debug_Is_owner_of_giant().
This is a preparation to remove the Giant lock.
Update #2555.
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Rename _ISR_Disable_without_giant() into _ISR_Local_disable(). Rename
_ISR_Enable_without_giant() into _ISR_Local_enable().
This is a preparation to remove the Giant lock.
Update #2555.
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Update #2556.
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The CPU time used of a thread was previously maintained per-processor
mostly during _Thread_Dispatch(). However, on SMP configurations the
actual processor of a thread is difficult to figure out since thread
dispatching is a highly asynchronous process (e.g. via inter-processor
interrupts). Only the intended processor of a thread is known to the
scheduler easily. Do the CPU usage accounting during thread heir
updates in the context of the scheduler operations. Provide the
function _Thread_Get_CPU_time_used() to get the CPU usage of a thread
using proper locks to get a consistent value.
Close #2627.
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Delete SCORE_INIT. This finally removes the
some.h:
#ifndef SOME_XYZ_EXTERN
#define SOME_XYZ_EXTERN extern
#endif
SOME_XYZ_EXTERN type xyz;
some_xyz.c:
#define SOME_XYZ_EXTERN
#include <some.h>
pattern in favour of
some.h:
extern type xyz;
some_xyz.c
#include <some.h>
type xyz;
Update #2559.
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Update #2408.
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This function is used by Newlib since 2013-07-09 (Git commit
9b51cd8c6b9cdd067d9648a7ab952884019c56a5).
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This was obsolete and broken based upon recent time keeping changes.
Thie build option was previously enabled by adding
USE_TICKS_FOR_STATISTICS=1 to the configure command line.
This propagated into the code as preprocessor conditionals
using the __RTEMS_USE_TICKS_FOR_STATISTICS__ conditional.
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The _Thread_Dispatch() function is quite complex and the time to set up
and tear down the stack frame is significant. Split this function into
two parts. The complex part is now in _Thread_Do_dispatch(). Call
_Thread_Do_dispatch() in _Thread_Enable_dispatch() only if necessary.
This increases the average case performance.
Simplify _Thread_Handler() for SMP configurations.
Update #2273.
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After a context switch we end up in the second part of
_Thread_Dispatch() or in _Thread_Handler() in case of new threads. Use
the same function _Thread_Restore_fp() to restore the floating-point
context. It makes no sense to do this in _Thread_Start_multitasking().
This fixes also a race condition in SMP configurations.
Update #2268.
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The current implementation of task migration in RTEMS has some
implications with respect to the interrupt latency. It is crucial to
preserve the system invariant that a task can execute on at most one
processor in the system at a time. This is accomplished with a boolean
indicator in the task context. The processor architecture specific
low-level task context switch code will mark that a task context is no
longer executing and waits that the heir context stopped execution
before it restores the heir context and resumes execution of the heir
task. So there is one point in time in which a processor is without a
task. This is essential to avoid cyclic dependencies in case multiple
tasks migrate at once. Otherwise some supervising entity is necessary to
prevent life-locks. Such a global supervisor would lead to scalability
problems so this approach is not used. Currently the thread dispatch is
performed with interrupts disabled. So in case the heir task is
currently executing on another processor then this prolongs the time of
disabled interrupts since one processor has to wait for another
processor to make progress.
It is difficult to avoid this issue with the interrupt latency since
interrupts normally store the context of the interrupted task on its
stack. In case a task is marked as not executing we must not use its
task stack to store such an interrupt context. We cannot use the heir
stack before it stopped execution on another processor. So if we enable
interrupts during this transition we have to provide an alternative task
independent stack for this time frame. This issue needs further
investigation.
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Use "cpu" for an arbitrary Per_CPU_Control variable.
Use "cpu_self" for the Per_CPU_Control of the current processor.
Use "cpu_index" for an arbitrary processor index.
Use "cpu_index_self" for the processor index of the current processor.
Use "cpu_count" for the processor count obtained via
_SMP_Get_processor_count().
Use "cpu_max" for the processor maximum obtained by
rtems_configuration_get_maximum_processors().
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The _Scheduler_SMP_Allocate_processor() and _Thread_Dispatch() exchange
information without locks. Make sure we use the right load/store
ordering.
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Use the Configuration instead.
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Use thread post-switch actions instead.
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Thread actions are the building block for efficient implementation of
- Classic signals delivery,
- POSIX signals delivery,
- thread restart notification,
- thread delete notification,
- forced thread migration on SMP configurations, and
- the Multiprocessor Resource Sharing Protocol (MrsP).
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Add per-CPU profiling stats API. Implement the thread dispatch disable
level profiling. The interrupt profiling must be implemented in CPU
port specific parts (mostly assembler code). Add a support function
_Profiling_Outer_most_interrupt_entry_and_exit() for this purpose.
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It is not necessary to load the executing thread control again after
the context switch since it is an invariant of the executing thread.
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Add and use _ISR_Disable_without_giant() and
_ISR_Enable_without_giant() if RTEMS_SMP is defined.
On single processor systems the ISR disable/enable was the big hammer
which ensured system-wide mutual exclusion. On SMP configurations this
no longer works since other processors do not care about disabled
interrupts on this processor and continue to execute freely.
On SMP in addition to ISR disable/enable an SMP lock must be used.
Currently we have only the Giant lock so we can check easily that ISR
disable/enable is used only in the right context.
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