These two fields in the thread structure control the preemptibility of a
thread.
sched_locked is decremented when the scheduler gets locked, which means
that the scheduler is locked for values 0xff to 0x01, since it can be
locked recursively. A thread is coop if its priority is negative, thus
if the prio field value is 0x80 to 0xff when looked at as an unsigned
value.
By putting them end-to-end, this means that a thread is non-preemptible
if the bundled value is greater than or equal to 0x0080. This is the
only thing the interrupt exit code has to check to decide to try a
reschedule or not.
Change-Id: I902d36c14859d0d7a951a6aa1bea164613821aca
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
Some thread fields were 32-bit wide, when they are not even close to
using that full range of values. They are instead changed to 8-bit fields.
- prio can fit in one byte, limiting the priorities range to -128 to 127
- recursive scheduler locking can be limited to 255; a rollover results
most probably from a logic error
- flags are split into execution flags and thread states; 8 bits is
enough for each of them currently, with at worst two states and four
flags to spare (on x86, on other archs, there are six flags to spare)
Doing this saves 8 bytes per stack. It also sets up an incoming
enhancement when checking if the current thread is preemptible on
interrupt exit.
Change-Id: Ieb5321a5b99f99173b0605dd4a193c3bc7ddabf4
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
This will allow for an enhancement when checking if the thread is
preemptible when exiting an interrupt.
Change-Id: If93ccd1916eacb5e02a4d15b259fb74f9800d6f4
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
That module is not used anymore: it was introduced pre-Zephyr to add
some kind of awareness when debugging ARM Cortex-M3 code with GDB but
was never really used by anyone. It has bitrotted, and with the recent
move of the tTCS and tNANO data structures to common _kernel and
k_thread, it does not even compile anymore.
Jira: ZEP-1284, ZEP-951
Change-Id: Ic9afed00f4229324fe5d2aa97dc6f1c935953244
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Some kernel operations, like scheduler locking can be optmized out,
since coop threads lock the scheduler by their very nature. Also, the
interrupt exit path for all architecture does not have to do any
rescheduling, again by the nature of non-preemptible threads.
Change-Id: I270e926df3ce46e11d77270330f2f4b463971763
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
The way the ready thread cache was implemented caused it to not always
be "hot", i.e. there could be some misses, which happened when the
cached thread was taken out of the ready queue. When that happened, it
was not replaced immediately, since doing so could mean that the
replacement might not run because the flow could be interrupted and
another thread could take its place. This was the more conservative
approach that insured that moving a thread to the cache would never be
wasted.
However, this caused two problems:
1. The cache could not be refilled until another thread context-switched
in, since there was no thread in the cache to compare priorities
against.
2. Interrupt exit code would always have to call into C to find what
thread to run when the current thread was not coop and did not have the
scheduler locked. Furthermore, it was possible for this code path to
encounter a cold cache and then it had to find out what thread to run
the long way.
To fix this, filling the cache is now more aggressive, i.e. the next
thread to put in the cache is found even in the case the current cached
thread is context-switched out. This ensures the interrupt exit code is
much faster on the slow path. In addition, since finding the next thread
to run is now always "get it from the cache", which is a simple fetch
from memory (_kernel.ready_q.cache), there is no need to call the more
complex C code.
On the ARM FRDM K64F board, this improvement is seen:
Before:
1- Measure time to switch from ISR back to interrupted task
switching time is 215 tcs = 1791 nsec
2- Measure time from ISR to executing a different task (rescheduled)
switch time is 315 tcs = 2625 nsec
After:
1- Measure time to switch from ISR back to interrupted task
switching time is 130 tcs = 1083 nsec
2- Measure time from ISR to executing a different task (rescheduled)
switch time is 225 tcs = 1875 nsec
These are the most dramatic improvements, but most of the numbers
generated by the latency_measure test are improved.
Fixes ZEP-1401.
Change-Id: I2eaac147048b1ec71a93bd0a285e743a39533973
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
This reverts commit
"kernel/arm: add comment about _is_next_thread_current"
and fixes the interrupt locking issue.
The comment would have been right if only reads were done the ready
queue, but that is not the case. It turns out that the comment was written
ignoring the fact that _is_next_thread_current() updates the next thread
cache when fetching the next thread.
Change-Id: I21c9230f85f4f87a6bbf14fd4a9eb7e19b59f8c5
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
Normally, _is_next_thread_current() must be called with interrupts
locked, but the ARM interrupt exit code does not have to do that. Add
explanation why.
Change-Id: Id383b47a055fdd6fbd5afffa52772e92febde98f
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
There was a lot of duplication between architectures for the definition
of threads and the "nanokernel" guts. These have been consolidated.
Now, a common file kernel/unified/include/kernel_structs.h holds the
common definitions. Architectures provide two files to complement it:
kernel_arch_data.h and kernel_arch_func.h. The first one contains at
least the struct _thread_arch and struct _kernel_arch data structures,
as well as the struct _callee_saved and struct _caller_saved register
layouts. The second file contains anything that needs what is provided
by the common stuff in kernel_structs.h. Those two files are only meant
to be included in kernel_structs.h in very specific locations.
The thread data structure has been separated into three major parts:
common struct _thread_base and struct k_thread, and arch-specific struct
_thread_arch. The first and third ones are included in the second.
The struct s_NANO data structure has been split into two: common struct
_kernel and arch-specific struct _kernel_arch. The latter is included in
the former.
Offsets files have also changed: nano_offsets.h has been renamed
kernel_offsets.h and is still included by the arch-specific offsets.c.
Also, since the thread and kernel data structures are now made of
sub-structures, offsets have to be added to make up the full offset.
Some of these additions have been consolidated in shorter symbols,
available from kernel/unified/include/offsets_short.h, which includes an
arch-specific offsets_arch_short.h. Most of the code include
offsets_short.h now instead of offsets.h.
Change-Id: I084645cb7e6db8db69aeaaf162963fe157045d5a
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
Not disabling SysTick as it is optional by the spec.
SVC not used as there is no priority-based interrupt masking (only
PendSV is used).
Largely based on a previous work done by Euan Mutch <euan@abelon.com>.
Jira: ZEP-783
Change-Id: I38e29bfcf0624c1aea5f9fd7a74230faa1b59e8b
Signed-off-by: Ricardo Salveti <ricardo.salveti@linaro.org>
The ARM architecture port is fitted with support for the unified kernel,
namely:
- the interrupt/exception exit code now pends PendSV if the current
thread is not a coop thread and if the scheduler is not locked
- fiber_abort is replaced by k_thread_abort(), which takes a thread ID
as a parameter (i.e. does not only operate on the current thread)
- the _nanokernel.flags cache of _current.flags is not used anymore
(could be a source of bugs) and is not needed in the scheduling algo
- there is no 'task' field in the _nanokernel anymore: PendSV not calls
_get_next_ready_thread instead
- the _nanokernel.fiber field is replaced by a more sophisticated
ready_q, based on the microkernel's priority-bitmap-based one
- thread initialization initializes new fields in the tcs, and does not
initialize obsolete ones
- nano_private includes nano_internal.h from the unified directory
- The FIBER, TASK and PREEMPTIBLE flags do not exist anymore: the thread
priority drives the behaviour
- the tcs uses a dlist for queuing in both ready and wait queues instead
of a custom singly-linked list
- other new fields in the tcs include a schedule-lock count, a
back-pointer to init data (when the task is static) and a pointer to
swap data, needed when a thread pending on _Swap() must be passed more
then just one value (e.g. k_stack_pop() needs an error code and data)
- the 'fiber' and 'task' fields of _nanokernel are replaced with an O(1)
ready queue (taken from the microkernel)
- fiberRtnValueSet() is aliased to _set_thread_return_value since it
also operates on preempt threads now
- _set_thread_return_value_with_data() sets the swap_data field in
addition to a return value from _Swap()
- convenience aliases are created for shorter names:
- _current is defined as _nanokernel.current
- _ready_q is defined as _nanokernel.ready_q
- _Swap() sets the threads's return code to -EAGAIN before swapping out
to prevent timeouts to have to set it (solves hard issues in some
kernel objects).
Change-Id: I36c03c362bc2908dae064ec67e6b8469fc573983
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
Removed old style file description and documnetation and apply
doxygen synatx.
Change-Id: I3ac9f06d4f574bf3c79c6f6044cec3a7e2f6e4c8
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Change all the Intel and Wind River code license from BSD-3 to Apache 2.
Change-Id: Id8be2c1c161a06ea8a0b9f38e17660e11dbb384b
Signed-off-by: Javier B Perez Hernandez <javier.b.perez.hernandez@linux.intel.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
Remove function name from comment and add @brief instead.
Also capitilize first letter.
Change-Id: Ib708b49bf02e5bc89b0066637a55874e659637e0
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Previous comment style used RETRURNS:, use @return to comply
with javadoc style.
Change-Id: Ib1dffd92da1d97d60063ec5309b08049828f6661
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
The change replaces multiple asterisks to ** at
the beginning of comments and adds a space before
the asterisks at the beginning of lines.
Change-Id: I7656bde3bf4d9a31e38941e43b580520432dabc1
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
The new name better reflects that this file contains all private
nanokernel APIs that are used by various kernel subsystems.
Change-Id: I4c258d582e93753eec9e575fdb5f9f2109417a0f
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
This commit set back .S as the assembly code extension for Kbuild.
Change-Id: Ib0119876bd0bed6617bbfbad2ca6a44e172ab042
Signed-off-by: Juan Manuel Cruz <juan.m.cruz.alcaraz@linux.intel.com>
Benjamin Walsh