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With this rework, we have two separate per-thread mode flags for
greater flexibility aimed at controlling the debug features on a
per-thread basis:

- T_WOSS can be set to trigger SIGDEBUG upon (unexpected) stage switch
  to in-band mode. This is strictly equivalent to the obsoleted T_WARN
  bit.

- T_WOLI enables/disables the detection of locking inconsistencies
  with mutexes via the EVL_THRIOC_{SET, CLEAR}_MODE interface. This
  combines the former static CONFIG_EVL_DEBUG_MUTEX_INBAND and
  CONFIG_EVL_DEBUG_MUTEX_SLEEP options.

Enabling CONFIG_EVL_DEBUG_WOLI turns on T_WOLI by default for every
new EVL thread running in userland, which can be opted out on a
per-thread basis using EVL_THRIOC_CLEAR_MODE.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

The new hierachy of priority scales is as follows:

EVL_CORE_MIN_PRIO = EVL_WEAK_MIN_PRIO
...
	EVL_FIFO_MIN_PRIO ==
	     EVL_QUOTA_MIN_PRIO ==
	          EVL_TP_MIN_PRIO (== 1)
	...
	EVL_FIFO_MAX_PRIO =
	     EVL_QUOTA_MAX_PRIO ==
	          EVL_TP_MAX_PRIO ==
		       EVL_WEAK_MAX_PRIO (< MAX_USER_RT_PRIO)
...
EVL_CORE_MAX_PRIO (> MAX_RT_PRIO)

We reserve a couple of priority levels above the highest inband
kthread priority (MAX_RT_PRIO..MAX_RT_PRIO+1), which are guaranteed to
be higher than the highest inband user task priority
(MAX_USER_RT_PRIO-1) we use for SCHED_FIFO. Those extra levels can be
used for EVL kthreads which must top the priority of any userland
thread.

SCHED_EVL was dropped int the process, since userland is now
constrained to EVL_FIFO_MAX_PRIO by construction.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Requires a couple of ABI changes.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

We don't plan for switching CPU from out-of-band context anymore, so
T_MOVED is basically pointless now.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

This protocol operates the monitor value as a set of boolean event
flags forming a 32bit-wide event group. All bits from a group are
initially set to zero.

An event flag group is a lightweight notification mechanism. The
application can send bitmasks to raise individual bits from the group
(i.e. group_value |= bits), or wait for the group to have at least one
bit set for satisfying the request. In the latter case, the group
value is read then cleared atomically, and the collected bits are
returned to the thread heading the wait queue.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Introduce a 'protocol' specifier for monitors along with a basic type
(gate or event), which userland can pass to change the way a monitor
can be signaled and awaited. Define PI/PP gates using this new
information bit associated to the generic EVL_MONITOR_GATE type.

With this change in, the pre-existing ungated event can be enriched
with additional protocols beyond the semaphore-based P/V operations.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

We may collect negative delta values when sampling latency on fast
machines, make sure the delta sum which is used in calculating the
average is signed, to prevent weird results.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Make sure breakage and/or WARN_ON() in the in-band transition code we
use for fixing up a trap on the oob stage cannot cause
handle_oob_trap() to be called recursively, leading to a stack
overflow eventually.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Jorge Ramirez-Ortiz authored Mar 28, 2019 and Philippe Gerum committed Jun 05, 2021

Elements:
--------
Basic features that cant be implemented from userland sharable between
processes.

Threads, monitors, xbufs and clocks -> every instance is backed by a
device in /dev/evl which allows sharing.

Utilities
---------
poll is a private-process construct; all poll groups are obtained from a
single multiplex device: /dev/evl/poll. They cannot be shared.

timers are in essence timerfd directly obtained from clocks, they don't
exist on their own, and are process-local too.

proxies are backed by a device in /dev/evl to allow for sharing, but
this is not something essential.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

The hectic utility needs to tell us whether some rtus/rtup/rtuo
threads are about to start waiting for an out-of-band event, so that
they don't miss a signal from the sleeper/switcher.

This information is now passed at UTASK registration time, which
ensures that HECTIC_OOB_WAIT is present in the task base flags early
enough before a SWITCH_TO request may target them.

Otherwise, the first evl_raise_flag() might be skipped in absence of
HECTIC_OOB_WAIT in the base flags of the target task, when the
sleeper/switcher manages to issue SWITCH_TO before such task enter the
PEND routine, which was seen at several occasions on very slow
platforms with 4+ CPUs (e.g. kvm-less qemu).

A typical test case involved running the following commands in
parallel on a 4-way configuration:

$ latmus
$ hectic rtuo2 rtuo3

In that case, tasks on CPU3 would miss the initial signal from the
sleeper/switcher.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

A significant portion of EVL is derived from Xenomai's cobalt core:
state this clearly and refer to https://xenomai.org

 in all related
files.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Since userland converted semaphore support to using ungated monitors,
we have no more users of the standalone semaphore element. Drop it.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

This is a special form of the wait operation which is not protected by
a lock. Userland is assumed to deal with signal-vs-wait races in its
own way.

An event value is now available from the monitor's state, which can be
tested for signedness as the fixed condition for waiting, which comes
in handy for implementing semaphore behavior. Plain flag-type behavior
could be implemented the same way.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

We want userland to receive EFAULT when bad pointers are passed to the
SET/GET operations, not SIGSEGV. So we need to handle any itimerspec
copy directly from kernel space.

At this chance, change the element name visible by userland from
"timerfd" to "timer", not to confuse people.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Combine the mapper and logger facilities into a single file proxy
element.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

There is no upside in sharing pollers between application processes,
since file descriptors are process-local handles in essence. Therefore
pollers are process-local utilities, so we don't need them to be
visible from the file system.

Downgrade the poller element to a plain single device from the
factory. Each open instance of such device is a polling channel. At
this chance, do a general rename from poller to poll, to match
commonly accepted naming.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

There is no upside in sharing loggers between application processes,
since they do not (and will not) deal with file locking. Therefore
loggers are process-local utilities, so we don't need them to be
visible from the file system.

Downgrade the logger element to a plain single device from the
factory. Each open instance of such device is a logging channel.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

No upside in measuring timeout delays differently than referring to
EVL_CLOCK_MONOTONIC. Let's converge to epoll_wait() in this respect.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Runtime mode setting is a self-applicable operation, and as such must
go through the control device where evl_current() implicitly applies.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Significant optimizations can happen only when acquire/release ops
involve single increment/decrement.

Although we loose the ability to implement read/write locking, we can
still do that using a monitor protecting an access map. So let's make
the semaphore code fast and right for the most common usage.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Philippe Gerum <rpm@xenomai.org>