Documentation specifies that aborting/terminating/exiting essential
threads is a system panic condition, but we didn't actually implement
that and allowed it as for other threads. At least one app wants to
exploit this documented behavior as a "watchdog" kind of condition,
and that seems reasonable. Do what we say we're supposed to do.
This also includes a small fix to a test, which seemed like it was
written to exercise exactly this condition. Except that it failed to
detect whether or not a system fatal error was actually signaled and
was (incorrectly) indicating "success". Check that we actually enter
the handler.
Fixes#45545
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
In order to bring consistency in-tree, migrate all kernel code to the
new prefix <zephyr/...>. Note that the conversion has been scripted,
refer to zephyrproject-rtos#45388 for more details.
Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
Implements a function that application and driver code can use to check
whether it is valid to yield (or block) in the current context. This
check is required for functions that can feasibly be run from multiple
contexts. The primary intended use case is power management transition
functions, which can be run by application code explicitly or
automatically in the idle thread by system PM.
Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
Do not allow changing the CPU which a thread is pinned when it is
already being executed. This allows further optimizations in some
platforms with incoherent memory since we can safely assume that the
thread will run in the same CPU and avoid invalidate / flush the
cache during context switches.
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
The original design intent with arch_sched_ipi() was that
interprocessor interrupts were fast and easily sent, so to reduce
latency the scheduler should notify other CPUs synchronously when
scheduler state changes.
This tends to result in "storms" of IPIs in some use cases, though.
For example, SOF will enumerate over all cores doing a k_sem_give() to
notify a worker thread pinned to each, each call causing a separate
IPI. Add to that the fact that unlike x86's IO-APIC, the intel_adsp
architecture has targeted/non-broadcast IPIs that need to be repeated
for each core, and suddenly we have an O(N^2) scaling problem in the
number of CPUs.
Instead, batch the "pending" IPIs and send them only at known
scheduling points (end-of-interrupt and swap). This semantically
matches the locations where application code will "expect" to see
other threads run, so arguably is a better choice anyway.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Add an API that clears cpu mask from a thread and sets it to a specific
CPU.
This is the equivelent of:
k_thread_cpu_mask_clear(&thread);
k_thread_cpu_mask_enable(&thread, cpu_idx);
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
This is an attempt at formally distinguishing and supporting the case
described in 40795 where an architecture doesn't preserve/restore the
complete thread state upon entering/exiting interrupt exception state.
This is mainly about promoting the current behavior from the accepted
workaround to a formal API specification. This workaround is currently
used on ARM64 but RISC-V requires it too.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Zephyr's timeslice implementation has always been somewhat primitive.
You get a global timeslice that applies broadly to the whole bottom of
the priority space, with no ability (beyond that one priority
threshold) to tune it to work on certain threads, etc...
This adds an (optionally configurable) API that allows timeslicing to
be controlled on a per-thread basis: any thread at any priority can be
set to timeslice, for a configurable per-thread slice time, and at the
end of its slice a callback can be provided that can take action.
This allows the application to implement things like responsiveness
heuristics, "fair" scheduling algorithms, etc... without requiring
that facility in the core kernel.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Moves the CONFIG_SCHED_THREAD_USAGE block of code out of sched.c
into its own file. Not only do they employ their own private
spin lock, but it is expected that additional usage routines will be
added in the future.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Move z_priq_mq_add and z_priq_mq_remove into #ifdef CONFIG_SCHED_MULTIQ
block, because they are only used with that config.
Signed-off-by: Jeremy Bettis <jbettis@google.com>
Applies the 'static' keyword to the following inlined routines:
z_priq_dumb_add()
z_priq_mq_add()
z_priq_mq_remove()
As those routines are only used in one place, they no longer have
externally visible declarations.
Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
Removed unused functions, or moved inside #ifdefs.
This allows using -Werror=unused-function on the clang compiler. Tested
by building the ChromeOS EC on all supported platforms with
-Werror=unused-functions.
Signed-off-by: Jeremy Bettis <jbettis@google.com>
It turns out that we have a sample (though not a test) that really
does want to use "k_thread_runtime_stats_all_get()" to measure system
uptime.
Instead of breaking this needlessly, separate the accounting for idle
and non-idle threads. The legacy API can report their sum, and the
more useful value is available via the kernel struct for future
analysis.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
The runtime stats feature has always supported this, so use the same
kconfig to indirect the timing source in the same way.
(Personally I'm not a fan of the "timing" API, which really doesn't do
anything that the existing core "cycles" API does not except add a
bunch of code due to the separate implementation of frequency
management and conversion routines. It comes from an era where
"cycles" were fixed to a MHz frequency clock on platforms like x86 yet
we had benchmarks that wanted to use the TSC. Those days are behind
us and "cycles" can be fast everywhere.)
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
On older architectures, we don't have the
architecture-independent/scheduler-internal hooks (which require
USE_SWITCH) but there is a hook shared by the tracing layer we can use.
This is sort of a layering violation (stat tracking is a core feature,
tracing is supposed to be optional), but simple and lightweight. And
eventually it will go away as these architectures migrate.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
This is an alternate backend that does what THREAD_RUNTIME_STATS is
doing currently, but with a few advantages:
* Correctly synchronized: you can't race against a running thread
(potentially on another CPU!) while querying its usage.
* Realtime results: you get the right answer always, up to timer
precision, even if a thread has been running for a while
uninterrupted and hasn't updated its total.
* Portable, no need for per-architecture code at all for the simple
case. (It leverages the USE_SWITCH layer to do this, so won't work
on older architectures)
* Faster/smaller: minimizes use of 64 bit math; lower overhead in
thread struct (keeps the scratch "started" time in the CPU struct
instead). One 64 bit counter per thread and a 32 bit scratch
register in the CPU struct.
* Standalone. It's a core (but optional) scheduler feature, no
dependence on para-kernel configuration like the tracing
infrastructure.
* More precise: allows architectures to optionally call a trivial
zero-argument/no-result cdecl function out of interrupt entry to
avoid accounting for ISR runtime in thread totals. No configuration
needed here, if it's called then you get proper ISR accounting, and
if not you don't.
For right now, pending unification, it's added side-by-side with the
older API and left as a z_*() internal symbol.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Some SMP applications have threading designs where every thread
created is always assigned to a specific CPU, and never want to
schedule them symmetrically across CPUs under any circumstance.
In this situation, it's possible to optimize the run queue design a
bit to put a separate queue in each CPU struct instead of having a
single global one. This is probably good for a few cycles per
scheduling event (maybe a bit more on architectures where cache
locality can be exploited) in circumstances where there is more than
one runnable thread. It's a mild optimization, but a basically simple
one.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Split "init_ready_q()" into a separate function that operates on the
queue pointer and not the global kernel object. Pure refactoring.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Similar to the previous patch, the various _priq_run_*() functions are
always passed a first argument that is the singleton system run queue
(this is because the same backend functions are used by wait queues).
Refactor into a simpler API that places the access to the run queue in
just a single spot.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Pure refactoring. For historical reasons these two functions took a
first argument (a pointer to the run queue) that was always the same.
Eliminate it.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
add a bitarray into struct osThreadDef_t to indicate whether the
thread is used or not, then we can get the first available thread
by searching this array when creating a new thread, and update this
array to add a free thread when terminating a thread.
Signed-off-by: Chen Peng1 <peng1.chen@intel.com>
Cadence XCC is based off of a very old 4.2 gcc compiler, which didn't
perfectly support C99 "inline" semantics with respect to
cross-translation-unit inline linkage (which Zephyr does not use, our
inlines are static only) and declaration order.
Fix the one spot where we were calling an inline before its
ALWAYS_INLINE definition, and add a flag to suppress the warning so
CI's trying to build with XCC and -Werror don't flip out.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
We cache the current thread ID in a thread-local variable
at thread entry, and have k_current_get() return that,
eliminating system call overhead for this API.
DL: changed _current to use z_current_get() as it is
being used during boot where TLS is not available.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Function types shall be in prototype form with named parameters
Found as a coding guideline violation (MISRA R8.2) by static
coding scanning tool.
Signed-off-by: Maksim Masalski <maksim.masalski@intel.com>
Fixes calculation of remaining ticks returned from z_tick_sleep
so that it takes absolute timeouts into account.
Fixes#32506
Signed-off-by: Lauren Murphy <lauren.murphy@intel.com>
In file include/kernel/thread.h in "struct _thread_base" is a member
called "_wait_q_t *pended_on"
At the same time in file kernel/sched.c is function called
"static _wait_q_t *pended_on()"
Coding scanning tool assigns violation (MISRA R5.9) that static
object reused, because thread.h is included in struct.c file.
I think we can rename function to avoid misreading in the future.
Signed-off-by: Maksim Masalski <maksim.masalski@intel.com>
The scheduler has historically had an API where an application can
inform the kernel that it will never create a thread that can be
preempted, and the kernel and architecture layer would use that as an
optimization hint to eliminate some code paths.
Those optimizations have dwindled to almost nothing at this point, and
they're now objectively a smaller impact than the special casing that
was required to handle the idle thread (which, obviously, must always
be preemptible).
Fix this by eliminating the idea of "cooperative only" and ensuring
that there will always be at least one preemptible priority with value
>=0. CONFIG_NUM_PREEMPT_PRIORITIES now specifies the number of
user-accessible priorities other than the idle thread.
The only remaining workaround is that some older architectures (and
also SPARC) use the CONFIG_PREEMPT_ENABLED=n state as a hint to skip
thread switching on interrupt exit. So detect exactly those platforms
and implement a minimal workaround in the idle loop (basically "just
call swap()") instead, with a big explanation.
Note that this also fixes a bug in one of the philosophers samples,
where it would ask for 6 cooperative priorities but then use values -7
through -2. It was assuming the kernel would magically create a
cooperative priority for its idle thread, which wasn't correct even
before.
Fixes#34584
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
_kernel struct can be used when multithreading is disabled.
In that case sched.c may not be compiled.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
Tests of a value against zero should be made explicit, unless the
operand is effectively Boolean. This is based on MISRA rule 14.4.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Add a 'U' suffix to values when computing and comparing against
unsigned variables and other related fixes of the same MISRA rule (10.4)
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
The clock/timer APIs are not application facing APIs, however, similar
to arch_ and a few other APIs they are available to implement drivers
and add support for new hardware and are documented and available to be
used outside of the clock/kernel subsystems.
Remove the leading z_ and provide them as clock_* APIs for someone
writing a new timer driver to use.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Wrap arch_sched_ipi() call in z_thread_abort() with ifdef checking for
hardware support of IPI.
Fixes#32723
Signed-off-by: Lauren Murphy <lauren.murphy@intel.com>
Due to the recent changes to scheduler z_find_first_thread_to_unpend
& z_remove_thread_from_ready_q are not used anymore. So removing the
dead code.
fixes: #32691
Signed-off-by: Spoorthy Priya Yerabolu <spoorthy.priya.yerabolu@intel.com>
These functions are a subset of proposed public APIs to clean up
several issues related to safely handling waking of threads. They
have been made private as they interface may change, but their use
will simplify the reimplementation of the k_work functionality.
See: https://github.com/zephyrproject-rtos/zephyr/pull/29668
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
`z_impl_k_yield` unlocked sched_spinlock, only to lock it again
immediately, do a little bit more work, then unlock it again.
This causes performance issues on SMP, where `sched_spinlock`
is often fairly highly contended and cores often end up spinning
for quite a while waiting to retake the lock in `z_swap_unlocked`.
Instead directly pass the spinlock key to `z_swap` and avoid the
extra lock+unlock.
Signed-off-by: James Harris <james.harris@intel.com>
`z_is_t1_higher_prio_than_t2` was being called twice in both the
context-switch fastpath and in `z_priq_rb_lessthan`, just to
dealing with priority ties. In addition, the API was error-prone
(and too much in the fastpath to be able to assert its invarients)
- see also #32710 for a previous example of this API breaking
and returning a>b but also b>a.
Replacing this with a direct 3-way comparison `z_cmp_t1_prio_with_t2`
sidesteps most of these issues. There is still a concern that
`sgn(z_cmp_t1_prio_with_t2(a,b)) != -sgn(z_cmp_t1_prio_with_t2(b,a))`
but I don't see any way to alleviate this aside from adding an
assert to the fastpath.
Signed-off-by: James Harris <james.harris@intel.com>
Previously two tasks with the same deadline and priority would
always have `z_is_t1_higher_prio_than_t2` `true` in both directions.
This is logically inconsistent, and results in `k_yield` not actually
yielding between identical threads.
Signed-off-by: James Harris <james.harris@intel.com>
Add a newer, much smaller and simpler implementation of abort and
join. No need to involve the idle thread. No need for a special code
path for self-abort. Joining a thread and waiting for an aborting one
to terminate elsewhere share an implementation. All work in both
calls happens under a single locked path with no unexpected
synchronization points.
This fixes a bug with the current implementation where the action of
z_sched_single_abort() was nonatomic, releasing the lock internally at
a point where the thread to be aborted could self-abort and confuse
the state such that it failed to abort at all.
Note that the arm32 and native_posix architectures, which have their
own thread abort implementations, now see a much simplified
"z_thread_abort()" internal API.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
THIS COMMIT DELIBERATELY BREAKS BISECTABILITY FOR EASE OF REVIEW.
SKIP IF YOU LAND HERE.
Remove the existing implementatoin of k_thread_abort(),
k_thread_join(), and the attendant facilities in the thread subsystem
and idle thread that support them.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
When the kernel is TICKLESS, timeouts are set as needed, and drivers
all have some minimum amount of time before which they can reliably
schedule an interrupt. When this happens, drivers will kick the
requested interrupt out by one tick. This means that it's not
reliably possible to get a timeout set for "one tick in the
future"[1].
And attempting to do that is dangerous anyway. If the driver will
delay a one-tick interrupt, then code that repeatedly tries to
schedule an imminent interrupt may end up in a state where it is
constantly pushing the interrupt out into the future, and timer
interrupts stop arriving! The timeout layer actually has protection
against this case.
Finally getting to the point: in recent changes, the timeslice layer
lost its integration with the "imminent" test in the timeout code, so
it's now able to run into this situation: very rapidly context
switching code (or rapidly arriving interrupts) will have the effect
of infinitely[2] delaying timeouts and stalling the whole timeout
subsystem.
Don't try to be fancy. Just clamp timeslice duration such that a
slice is 2 ticks at minimum and we'll never hit the problem. Adjust
the two tests that were explicitly requesting very short slice rates.
[1] Of course, the tradeoff is that the tick rate can be 100x higher
or more, so on balance tickless is a huge win.
[2] Actually it only lasts until a 31 bit signed rollover in the HPET
cycle count in practice.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Recent work to normalize use of the thread QUEUED state bit means that
we never attempt to remove unqueued threads from the low-level run
queue. So the old workaround for SWAP_NONATOMIC that was trying to
detect this condition isn't necessary anymore.
Which is serendipitous, because it was written to encode some very
specific logic about the circumstances where _current could be
dequeued that I'd like to be able to break.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
This is part of the scheduler API, and was always just a synchronized
wrapper around the internal ready_thread() function. But where the
internal users seem to be careful not to call it on threads that are
not known to be already queued or running, the general users in the
IPC code seem to be less strict.
Add a simple test to detect the case where a thread is already
running. Right now this just loops over the array of CPUs, so is O(N)
in the CPU count even though N is never more than four for us
currently. But this is possible without modifying data structures. A
more scalable way to do this if we ever need to run on very parallel
systems would be to use another state bit for RUNNING, or to keep a
backpointer in the thread struct to the CPU it's running on, etc...
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
Swap was originally written to use the scheduler lock just to select a
new thread, but it would be nice to be able to rely on scheduler
atomicity later in the process (in particular it would be nice if the
assignment to cpu.current could be seen atomically). Rework the code
a bit so that swap takes the lock itself and holds it until just
before the call to arch_switch().
Note that the local interrupt mask has always been required to be held
across the swap, so extending the lock here has no effect on latency
at all on uniprocessor setups, and even on SMP only affects average
latency and not worst case.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
