When this new Kconfig option is enabled, preempted threads on an SMP
system may generate additional IPIs when they are switched out.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
The deadline of deadline scheduler should lager than zero
because if deadline is negative, it menas the task should
be finished in past.
Signed-off-by: TaiJu Wu <tjwu1217@gmail.com>
Platforms that support IPIs allow them to be broadcast via the
new arch_sched_broadcast_ipi() routine (replacing arch_sched_ipi()).
Those that also allow IPIs to be directed to specific CPUs may
use arch_sched_directed_ipi() to do so.
As the kernel has the capability to track which CPUs may need an IPI
(see CONFIG_IPI_OPTIMIZE), this commit updates the signalling of
tracked IPIs to use the directed version if supported; otherwise
they continue to use the broadcast version.
Platforms that allow directed IPIs may see a significant reduction
in the number of IPI related ISRs when CONFIG_IPI_OPTIMIZE is
enabled and the number of CPUs increases. These platforms can be
identified by the Kconfig option CONFIG_ARCH_HAS_DIRECTED_IPIS.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
The CONFIG_IPI_OPTIMIZE configuration option allows for the flagging
and subsequent signaling of IPIs to be optimized.
It does this by making each bit in the kernel's pending_ipi field
a flag that indicates whether the corresponding CPU might need an IPI
to trigger the scheduling of a new thread on that CPU.
When a new thread is made ready, we compare that thread against each
of the threads currently executing on the other CPUs. If there is a
chance that that thread should preempt the thread on the other CPU
then we flag that an IPI is needed for that CPU. That is, a clear bit
indicates that the CPU absolutely will not need to reschedule, while a
set bit indicates that the target CPU must make that determination for
itself.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
1. The flagging of IPIs is moved out of k_thread_priority_set() into
z_thread_prio_set(). This allows for an IPI to be done for a thread
that had its priority bumped due to the handling of priority
inheritance from a mutex.
2. k_thread_priority_set()'s check for sched_locked only applies to
non-SMP builds that are using the old arch_swap() framework to switch
between threads.
Incidentally, nearly all calls to flag_ipi() are now performed with
sched_spinlock being locked. The only exception is in slice_timeout().
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Namespaced the generated headers with `zephyr` to prevent
potential conflict with other headers.
Introduce a temporary Kconfig `LEGACY_GENERATED_INCLUDE_PATH`
that is enabled by default. This allows the developers to
continue the use of the old include paths for the time being
until it is deprecated and eventually removed. The Kconfig will
generate a build-time warning message, similar to the
`CONFIG_TIMER_RANDOM_GENERATOR`.
Updated the includes path of in-tree sources accordingly.
Most of the changes here are scripted, check the PR for more
info.
Signed-off-by: Yong Cong Sin <ycsin@meta.com>
The previous abort-lifecycle fix missed a case: other threads can
enter k_thread_join(), see that the thread is already dead, and then
need to call z_thread_switch_spin() to wait for a context switch. But
the new "dummification" code was (by design!) terminating the thread
such that no context would be saved to it. So switch_handle stayed
NULL and if you hit that timing case correctly[1] you'd deadlock
waiting for a switch that would never come.
Fix is just to set switch_handle when dummifying to any non-NULL
value.
Also add an assertion to catch the obvious case that a thread is
actually dead on the exit path of k_thread_abort() to make sure the
variant path continues to set flags correctly
[1] CI was doing it fairly reliably via tests/kernel/smp_abort on
qemu_cortex_a53 only. Only one of my dev systems could see it,
and then only about 15% of the time.
Signed-off-by: Andy Ross <andyross@google.com>
We've had threads spinning on the thread state bits, but weren't being
careful to ensure that those bits were the last things seen to change
in a halting thread. Move it to the end, and add a barrier for
correctness.
Signed-off-by: Andy Ross <andyross@google.com>
Nicolas Pitre points out that since these thread structs are just
dummies for the context swtiching, they can be presumed to be "write
only" and thus there's no point in having one per CPU, everyone can
share the same one.
The only gotcha is that we never really documented (nor really have a
place to document) that rule, so it's not theoretically impossible for
an architecture to read back what it might have written underneath
arch_switch(). Leave this in a separate commit for bisection
purposes, but the risk seems very low.
Signed-off-by: Andy Ross <andyross@google.com>
After a k_thread_abort(), the resulting thread struct is documented as
unused/free memory that may be re-used (for example, to respawn a new
thread).
But in the special case of aborting the current thread from within an
ISR, that wasn't quite happening. The scheduler cleanup would
complete, but the architecture layer would still try to context switch
away from the aborted thread on exit, and that can include writes to
the now-reused thread struct! The specifics will depend on
architecture (some do a full context save on entry, most don't), but
in the case of USE_SWITCH=y it will at the very least write the
switch_handle field.
Fix this simply, with a per-cpu "switch dummy" thread struct for use
as a target for context switches like this. There is some non-trivial
memory cost to that; thread structs on many architectures are large.
Pleasingly, this also addresses a known deadlock on SMP: because the
"spin in ISR" step now happens as the very last stage of
k_thread_abort() handling, the existing scheduler lock works to
serialize calls such that it's impossible for a cycle of threads to
independently decide to spin on each other: at least one will see
itself as "already aborting" and break the cycle.
Fixes#64646
Signed-off-by: Andy Ross <andyross@google.com>
Updates z_get_next_switch_handle() to set the new thread's base.cpu
value as it is done in do_swap(). This helps to ensure that the
last CPU on which the thread executed remains current.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
This reverts commit 61c70626a5.
This PR introduced 2 regressions in main CI:
71977 & 71978
Let's revert it by now to get main's CI passing again.
Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
This reverts commit 20611f13ca.
This PR introduced 2 regressions in main CI:
71977 & 71978
Let's revert it by now to get main's CI passing again.
Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
This reverts commit 02b24911f7.
This PR introduced 2 regressions in main CI:
71977 & 71978
Let's revert it by now to get main's CI passing again.
Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
We've had threads spinning on the thread state bits, but weren't being
careful to ensure that those bits were the last things seen to change
in a halting thread. Move it to the end, and add a barrier for
correctness.
Signed-off-by: Andy Ross <andyross@google.com>
Nicolas Pitre points out that since these thread structs are just
dummies for the context swtiching, they can be presumed to be "write
only" and thus there's no point in having one per CPU, everyone can
share the same one.
The only gotcha is that we never really documented (nor really have a
place to document) that rule, so it's not theoretically impossible for
an architecture to read back what it might have written underneath
arch_switch(). Leave this in a separate commit for bisection
purposes, but the risk seems very low.
Signed-off-by: Andy Ross <andyross@google.com>
After a k_thread_abort(), the resulting thread struct is documented as
unused/free memory that may be re-used (for example, to respawn a new
thread).
But in the special case of aborting the current thread from within an
ISR, that wasn't quite happening. The scheduler cleanup would
complete, but the architecture layer would still try to context switch
away from the aborted thread on exit, and that can include writes to
the now-reused thread struct! The specifics will depend on
architecture (some do a full context save on entry, most don't), but
in the case of USE_SWITCH=y it will at the very least write the
switch_handle field.
Fix this simply, with a per-cpu "switch dummy" thread struct for use
as a target for context switches like this. There is some non-trivial
memory cost to that; thread structs on many architectures are large.
Pleasingly, this also addresses a known deadlock on SMP: because the
"spin in ISR" step now happens as the very last stage of
k_thread_abort() handling, the existing scheduler lock works to
serialize calls such that it's impossible for a cycle of threads to
independently decide to spin on each other: at least one will see
itself as "already aborting" and break the cycle.
Fixes#64646
Signed-off-by: Andy Ross <andyross@google.com>
Big change is to factor out a thread_halt_spin() utility to manage the
core complexity of this code: the situation where an ISR is asked to
abort a thread already running on another SMP CPU.
With that gone, things can be cleaned up quite a bit. Remove early
returns, most of the "#if CONFIG_SMP" usage was superfluous and will
optimize out, unify and clean up the comments, etc...
No behavioral changes (hopefully), just refactoring.
Signed-off-by: Andy Ross <andyross@google.com>
After the move to C files we got some drop in the performance when
running latency_measure. This patch declares the priority queue
functions as static inlines with minor optimizations.
The result for one metric (on qemu):
3.6 and before the anything was changed:
Get data from LIFO (w/ ctx switch): 13087 ns
after original change (46484da502):
Get data from LIFO (w/ ctx switch): 13663 ns
with this change:
Get data from LIFO (w/ ctx switch): 12543 ns
So overall, a net gain of ~ 500ns that can be seen across the board on many
of the metrics.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
This adds the mechanism to do cleanup after k_thread_abort()
is called with the current thread. This is mainly used for
cleaning up things when the thread cannot be running, e.g.,
cleanup the thread stack.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Do not build threading support when CONFIG_MULTITHREADING=n is set and
move needed calls to a new file with the changes needed instead of the
ifdef party in sched.c
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Add a closing comment to the endif with the configuration
information to which the endif belongs too.
To make the code more clearer if the configs need adaptions.
Signed-off-by: Simon Hein <Shein@baumer.com>
k_thread_deadline_set() would modify the thread's deadline and then,
if it was in the run queue, requeue it to put it at the right spot.
Sounds right, right?
It's wrong. The deadline field is part of the thread priority, so
this results in a mis-ordered list. For dlist backends, that's benign
as the removal works anyway, but if CONFIG_SCHED_SCALABLE=y we've now
broken the sorting order of an in-tree item and corrupted the rbtree!
Fixes#69935
Signed-off-by: Andy Ross <andyross@google.com>
Rename private function to make it clear what priority we are setting
and to be consistent across the code.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Avoid single characker variables that renders code unreadable and might
cause conflicts in maing, similar to t for both timeout and thread in
some places.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Use thread wherever it makes sense, using 't' in some places can get
confused with 't' used for timeouts for example.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Move thread monitor related functions, not enabled in most cases outside
of thread.c and cleanup headers.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
This function is only being used by a test, so instead of reimplementing
a syscall in the test, provide a Kconfig option to provide the
functionality that only works with tests and remove some of the
duplication and extra code.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
We shouldn't be calling hooks from optional and upper layer subsystems
in the kernel, instead, just call the hook to set thread status in the
API where it is needed.
This now clears related bit in cmsis thread status bitarray when
terminating a thread in the cmsis rtos v1 layer directly and not in the
kenrel code.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
In an effort to cleanup sched.c, move sections of code that can be
compiled in based on options into own files. CPU mask here is managed by
a kconfig and is not widely used (SMP affinity on multicore systems).
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
The functions to manipulate the essential flag indeed operate on
threads, but they are misplaced in the thread implementation file. Put
them alongside other routines setting other thread flags and cleanup
headers a bit.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
clean up headers under include/ and move handling of priority queue to
own file/header.
No need for the header include/zephyr/kernel/internal/sched_priq.h
anymore. Move the relevant structures where they are being used in
kernel_structs.h.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
This commit does two things to k_wakeup():
1. It locks the scheduler before marking the thread as not suspended.
As the the clearing of the _THREAD_SUSPENDED bit is not atomic, this
helps ensure that neither another thread nor ISR interrupts this
action (resulting in a corrupted thread_state).
2. The call to flag_ipi() has been removed as it is already being
made within ready_thread().
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
The current z_tick_sleep return directly when building kernel for Single
Thread model. This reorganize the code to use k_busy_wait() to be time
coherent since subsystems may depend on it.
In the case of a K_FOREVER timeout is selected the Single Thread the
implementation will invoke k_cpu_idle() and the system will wait for
an interrupt saving power.
Signed-off-by: Gerson Fernando Budke <gerson.budke@ossystems.com.br>
Updates both the k_sleep() and k_usleep() return values so that if
the thread was woken up prematurely, they will return the time left
to sleep rounded up to the nearest millisecond (for k_sleep) or
microsecond (for k_usleep) instead of rounding down. This removes
ambiguity should there be a non-zero number of remaining ticks
that correlate to a time of less than 1 millisecond or 1 microsecond.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Extends the concept of halting a thread from just aborting a thread
to both aborting and suspending a thread.
Part of this involves updating k_thread_suspend() to operate in a
similar fashion to that of k_thread_abort().
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Extracts the essential thread synchronization logic when aborting
a thread from z_thread_abort() and moves it to its own routine
called z_thread_halt().
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
The routine halt_thread() acts nearly identical to end_thread()
except that instead of only halting the thread if the _THREAD_DEAD
state bit is not set, it will halt it if bit specified by the
parameter new_state is not set (which is always _THREAD_DEAD).
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Peter Mitsis
TaiJu Wu
Yong Cong Sin
Hess Nathan
Andy Ross
Alberto Escolar Piedras
Anas Nashif
Daniel Leung
Simon Hein
Gerson Fernando Budke
Gaetan Perrot