| Commit message (Collapse) | Author | Age |
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If a task is released on a CPU that is idle, then it is pointless to
send an IPI to another CPU just to schedule the newly released task.
This patch changes check_for_preemptions() to prefer the local CPU
first if it is idle.
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The 'time_slice' parameter has not been relevant in a couple of years.
The 'completed' flag was misused in a few places. This clean-up patch
removes these outdated remnants.
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In the task_new() handler, don't process a job arrival event if the
task is actually suspended. This fixes the admission of suspended
tasks.
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Tasks can now be PERIODIC or SPORADIC.
PERIODIC tasks do not have their job number incremented
when they wake up and are tardy. PERIODIC jobs must
end with a call to sys_complete_job() to set up their next
release. (Not currently supported by pfair.)
SPORADIC tasks _do_ have their job number incremented when
they wake up and are tardy. SPORADIC is the default task
behavior, carrying forward Litmus's current behavior.
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This patch allows a task to request early releasing
via rt_task parameters to sys_set_task_rt_param().
Note that early releasing can easily peg your CPUs
since early-releasing tasks never suspend to wait for
their next job. As such, early releasing is really
only useful in the context of implementing bandwidth
servers, interrupt handling threads (or any thread that
spends most of its time waiting for an event), or
short-lived computations. If early releasing pegs your
CPUs, then you probably shouldn't be using it.
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Nesting of locks was never supported in LITMUS^RT since
the required analysis does not exist anyway. That is, as
defined in the literature, the protocols implemented
in LITMUS^RT have not been studied in conjunction with
nested critical sections.
In LITMUS^RT, attempting to nest locks could lead to
silent or not-so-silent bugs. This patch makes this
restriction explicit and returns EBUSY when a process
attempts to nest resources.
This is enforced on a protocol-by-protocol basis,
which means that adding protocols with support for
nesting in future versions is not affected by this
change.
Exception: PCP and SRP resources may be nested,
but not within global critical sections.
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This patch removes the RT_F_EXIT_SEM flag. All code paths
depending on it being true are assumed to be unreachable
and removed.
The 'flags' field in struct rt_params is left as-is for
use by specific schedulers. For example, sched_pfair
defines a custom flag RT_F_REQUEUE within the 'flags'
field.
Signed-off-by: Manohar Vanga <mvanga@mpi-sws.org>
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This patch removes the flags RT_F_SLEEP and RT_F_RUNNING
as their name is misleading. This patch replaces them with
a 'completed' field in struct rt_param.
Signed-off-by: Manohar Vanga <mvanga@mpi-sws.org>
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This patch changes how preemptions of jobs without
budget work. Instead of requeuing them, they are now
only added if they are not subject to budget enforcement
or if they have non-zero budget. This allows us to process
job completions that race with preemptions.
This appears to fix a BUG in budget.c:65 reported by Giovani Gracioli.
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litmus.h is accumulating too many things. Since
we already have budget.h, let's stick all budget-related
inline functions there as well.
This patch is merely cosmetic; it does not change
how budget enforcement works.
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Needed to update C-EDF to handle release master. Also
updated get_nearest_available_cpu() to take NO_CPU instead
of -1 to indicate that there is no release master. While
NO_CPU is 0xffffffff (-1 in two's complement), we still
translate this value to -1 in case NO_CPU changes.
Signed-off-by: Andrea Bastoni <bastoni@cs.unc.edu>
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Given a choice between several available CPUs (unlinked) on which
to schedule a task, let the scheduler select the CPU closest to
where that task was previously scheduled. Hopefully, this will
reduce cache migration penalties.
Notes: SCHED_CPU_AFFINITY is dependent upon x86 (only x86 is
supported at this time). Also PFair/PD^2 does not make use of
this feature.
Signed-off-by: Andrea Bastoni <bastoni@cs.unc.edu>
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Otherwise, the release master CPU may try to reschedule in an infinite
loop.
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The next owner of a FMLP-protected resource is dequeued from
the FMLP FIFO queue by unlock() (when the resource is freed by
the previous owner) instead of performing the dequeue by the next
owner immediately after it has been woken up.
This simplifies the code a little bit and also reduces potential
spinlock contention.
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As Glenn pointed out, it is useful for some protocols (e.g.,
k-exclusion protocols) to know the userspace configuration at object
creation time. This patch changes the fdso API to pass the parameter
to the object constructor, which is then in turn passed to the lock
allocater. The return code from the lock allocater is passed to
userspace in return.
This also fixes some null pointer dereferences in the FDSO code found
by the test suite in liblitmus.
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This introduces the global FMLP based on the generic locking layer.
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This renders the FMLP and SRP unfunctional until they are ported to
the new locking API.
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Linux now has a macro of the same name, which causes namespace
collisions. Since our version is only being used in two places that
haven't triggered in several years, let's just remove it.
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To date, Litmus has just hooked into the smp_send_reschedule() IPI
handler and marked tasks as having to reschedule to implement remote
preemptions. This was never particularly clean, but so far we got away
with it. However, changes in the underlying Linux, and peculartities
of the ARM code (interrupts enabled before context switch) break this
naive approach. This patch introduces new state-machine based remote
preemption support. By examining the local state before calling
set_tsk_need_resched(), we avoid confusing the underlying Linux
scheduler. Further, this patch avoids sending unncessary IPIs.
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Introduces CONFIG_RELEASE_MASTER and makes release
master support dependent on the new symbol. This is
useful because dedicated interrupt handling only applies
to "large" multicore platforms. This will allow us to
not implement smp_send_pull_timers() for all platforms.
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NO_ENFORCEMENT - A job may execute beyond its declared execution time.
Jobs notify the kernel that they are complete via liblitmus's
sleep_next_period()
QUANTUM_ENFORCEMENT - The kernel terminates a job if its actual execution
time exceeds the declared execution time.
PRECISE_ENFORCEMENT - Hook declared, but not yet implemented. Plan to
support this policy through hrtimers. Error thrown if specified.
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Adapt to new schema for spinlock:
(tglx 20091217)
spinlock - the weakest one, which might sleep in RT
raw_spinlock - spinlock which always spins even on RT
arch_spinlock - the hardware level architecture dependent implementation
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Most probably, all the spinlocks changed by this commit will be true
spinning lock (raw_spinlock) in PreemptRT (so hopefully we'll need few
changes when porting Litmmus to PreemptRT).
There are a couple of spinlock that the kernel still defines as
spinlock_t (therefore no changes reported in this commit) that might cause
us troubles:
- wait_queue_t lock is defined as spinlock_t; it is used in:
* fmlp.c -- sem->wait.lock
* sync.c -- ts_release.wait.lock
- rwlock_t used in fifo implementation in sched_trace.c
* this need probably to be changed to something always spinning in RT
at the expense of increased locking time.
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This commit also fixes warnings and errors due to the need to include
slab.h when using kmalloc() and friends.
----
This commit does not compile.
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This patch updates non-preemptive section support in
GSN- and PSN-EDF.
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Having GSN-EDF log so many things each tick is useful
when tracking down race conditions, but it also makes
it really hard to find anything else. Thus, turn it off by
default but leave it in for future debugging fun.
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- Binomial heap "heap" names conflicted with priority heap
of cgroup in kernel
- This patch change binomial heap "heap" names in "bheap"
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- insert arm_release_timer() in add_relese() path
- arm_release_timer() uses __hrtimer_start_range_ns() instead of
hrtimer_start() to avoid deadlock on rq->lock.
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