| Commit message (Collapse) | Author | Age |
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...and also finally fix the requeue() race (hopefully).
Commit 4ffefb822b9d65d4efbedb60e3c9a0e76895cc5b broke the synchronous
task system release code. The problem is that release_at() clears the
tsk_rt(t)->completed flag. The patch thus only made the race window
smaller, but didn't close it entirely. Further, it broke the
synchronous task set release, which relies on schedule() being called
with completed == 1.
This patch fixes both problems by introducing a new flag dont_requeue,
which indicates unambiguously that a task should not be requeued by
other processors. This flag is cleared only when the job completion is
being processed, which always happens while holding the appropriate
scheduler locks, which closes the race window.
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To avoid compile errors if locking support is disabled, and to avoid
having to use #ifdef each time is_priority_boosted() is used.
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EARLY in release_policy_t was conflicting with
other kernel constants.
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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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Allow tracing of NULL tasks. Makes debugging a bit easier.
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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 fixes the compiler warning about struct litmus_locking
being defined in the parameter list when CONFIG_LITMUS_LOCKING is
not set.
Signed-off-by: Manohar Vanga <mvanga@mpi-sws.org>
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Stop hard-to-detect out-of-bounds errors early.
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SEND_RESCHED_END is necessarily preceded by an interrupt. We don't
want to filter events based on this expected interrupts, but we still
want to detect samples disturbed by other interrupts. Hence, subtract
one off the interrupt count.
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To detect interrupts that interfered after the initial time stamp was
recorded, this patch changes sched_trace to also record the IRQ count
as observed by userspace.
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Also add some compile-time checks to detect unexpected offsets.
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Support recording timestamps that allow tracing the entry and exit
costs of locking-related system calls.
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Reassing locking timestamps and prepare support for tracing
system call overheads.
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To properly trace locking overheads, it is required to tell apart
samples from different tasks, which requires keeping track of their
PIDs.
The timestamp is shortened to 48 bits to make room for the PID.
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The LITMUS^RT-specific completion API complete_n() is no longer
required by the synchronous release code. Let's remove it; one less
modification of a core Linux file to maintain during rebasing.
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Commit e6f51fb826ce98d436f445aae4eb9e9dba1f30e8 added some floating
point support for LITMUS^RT, but it used 64-bit division that ARM does
not support. Therefore, use the division functions from math64.h.
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Instead of tie-breaking by PID (which is a static
priority tie-break), we can tie-break by other
job-level-unique parameters. This is desirable
because tasks are equaly affected by tardiness
since static priority tie-breaks cause tasks
with greater PID values to experience the most
tardiness.
There are four tie-break methods:
1) Lateness. If two jobs, J_{1,i} and J_{2,j} of
tasks T_1 and T_2, respectively, have equal
deadlines, we favor the job of the task that
had the worst lateness for jobs J_{1,i-1} and
J_{2,j-1}.
Note: Unlike tardiness, lateness may be less than
zero. This occurs when a job finishes before its
deadline.
2) Normalized Lateness. The same as #1, except
lateness is first normalized by each task's
relative deadline. This prevents tasks with short
relative deadlines and small execution requirements
from always losing tie-breaks.
3) Hash. The job tuple (PID, Job#) is used to
generate a hash. Hash values are then compared.
A job has ~50% chance of winning a tie-break
with respect to another job.
Note: Emperical testing shows that some jobs
can have +/- ~1.5% advantage in tie-breaks.
Linux's built-in hash function is not totally
a uniform hash.
4) PIDs. PID-based tie-break used in prior
versions of Litmus.
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Added support for arbitrary deadlines.
Constraint: Relative deadline must be >= exec cost.
Use: Set relative deadline in rt_task::rdeadline. Set value to 0
to default to implicit deadlines.
Limitations: PFAIR not supported by this patch. PFAIR updated to
reject tasks that do not have implicit deadlines.
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Add a comment to explain how priorities are
interpreted, and provide some useful macros for
userspace.
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Prior to that it was only used internally for DPCP
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dissertation (branch bbb-diss) to current
version of litmus
This is needed for ongoing projects
I took the unchanged code but removed some leftovers
of OMLP which is not implemented
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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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An efficient binary heap implementation coded in the
style of Linux's list. This binary heap should be able
to replace any partially sorted priority queue based
upon Linux's list.
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Enable kernel-style events (tracepoint) for Litmus. Litmus events
trace the same functions as the sched_trace_XXX(), but can be
enabled independently.
So, why another tracing infrastructure then:
- Litmus tracepoints can be recorded and analyzed together (single
time reference) with all other kernel tracing events (e.g.,
sched:sched_switch, etc.). It's easier to correlate the effects
of kernel events on litmus tasks.
- It enables a quick way to visualize and process schedule traces
using trace-cmd utility and kernelshark visualizer.
Kernelshark lacks unit-trace's schedule-correctness checks, but
it enables a fast view of schedule traces and it has several
filtering options (for all kernel events, not only Litmus').
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Increment a processor-local counter whenever an interrupt is handled.
This allows Feather-Trace to include a (truncated) counter and a flag
to report interference from interrupts. This could be used to filter
samples that were disturbed by interrupts.
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User a 32-bit word for all non-preemptive section flags.
Set the "please yield soon" flag atomically when
accessing it on remotely-scheduled tasks.
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This allows us to splice in information into logs from events
that were recorded in userspace.
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Preemption state tracing is only useful when debugging preemption-
and IPI-related races. Since it creates a lot of clutter in the logs,
this patch turns it off unless explicitly requested.
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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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Original comment said that this feature wasn't supported,
though it has been since around October 2010.
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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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Some notes:
* Litmus^RT scheduling class is the topmost scheduling class
(above stop_sched_class).
* scheduler_ipi() function (e.g., in smp_reschedule_interrupt())
may increase IPI latencies.
* Added path into schedule() to quickly re-evaluate scheduling
decision without becoming preemptive again. This used to be
a standard path before the removal of BKL.
Conflicts:
Makefile
arch/arm/kernel/calls.S
arch/arm/kernel/smp.c
arch/x86/include/asm/unistd_32.h
arch/x86/kernel/smp.c
arch/x86/kernel/syscall_table_32.S
include/linux/hrtimer.h
kernel/printk.c
kernel/sched.c
kernel/sched_fair.c
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
signal: align __lock_task_sighand() irq disabling and RCU
softirq,rcu: Inform RCU of irq_exit() activity
sched: Add irq_{enter,exit}() to scheduler_ipi()
rcu: protect __rcu_read_unlock() against scheduler-using irq handlers
rcu: Streamline code produced by __rcu_read_unlock()
rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special
rcu: decrease rcu_report_exp_rnp coupling with scheduler
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git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/urgent
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The RCU_BOOST commits for TREE_PREEMPT_RCU introduced an other-task
write to a new RCU_READ_UNLOCK_BOOSTED bit in the task_struct structure's
->rcu_read_unlock_special field, but, as noted by Steven Rostedt, without
correctly synchronizing all accesses to ->rcu_read_unlock_special.
This could result in bits in ->rcu_read_unlock_special being spuriously
set and cleared due to conflicting accesses, which in turn could result
in deadlocks between the rcu_node structure's ->lock and the scheduler's
rq and pi locks. These deadlocks would result from RCU incorrectly
believing that the just-ended RCU read-side critical section had been
preempted and/or boosted. If that RCU read-side critical section was
executed with either rq or pi locks held, RCU's ensuing (incorrect)
calls to the scheduler would cause the scheduler to attempt to once
again acquire the rq and pi locks, resulting in deadlock. More complex
deadlock cycles are also possible, involving multiple rq and pi locks
as well as locks from multiple rcu_node structures.
This commit fixes synchronization by creating ->rcu_boosted field in
task_struct that is accessed and modified only when holding the ->lock
in the rcu_node structure on which the task is queued (on that rcu_node
structure's ->blkd_tasks list). This results in tasks accessing only
their own current->rcu_read_unlock_special fields, making unsynchronized
access once again legal, and keeping the rcu_read_unlock() fastpath free
of atomic instructions and memory barriers.
The reason that the rcu_read_unlock() fastpath does not need to access
the new current->rcu_boosted field is that this new field cannot
be non-zero unless the RCU_READ_UNLOCK_BLOCKED bit is set in the
current->rcu_read_unlock_special field. Therefore, rcu_read_unlock()
need only test current->rcu_read_unlock_special: if that is zero, then
current->rcu_boosted must also be zero.
This bug does not affect TINY_PREEMPT_RCU because this implementation
of RCU accesses current->rcu_read_unlock_special with irqs disabled,
thus preventing races on the !SMP systems that TINY_PREEMPT_RCU runs on.
Maybe-reported-by: Dave Jones <davej@redhat.com>
Maybe-reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
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Allow for sched_domain spans that overlap by giving such domains their
own sched_group list instead of sharing the sched_groups amongst
each-other.
This is needed for machines with more than 16 nodes, because
sched_domain_node_span() will generate a node mask from the
16 nearest nodes without regard if these masks have any overlap.
Currently sched_domains have a sched_group that maps to their child
sched_domain span, and since there is no overlap we share the
sched_group between the sched_domains of the various CPUs. If however
there is overlap, we would need to link the sched_group list in
different ways for each cpu, and hence sharing isn't possible.
In order to solve this, allocate private sched_groups for each CPU's
sched_domain but have the sched_groups share a sched_group_power
structure such that we can uniquely track the power.
Reported-and-tested-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-08bxqw9wis3qti9u5inifh3y@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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In order to prepare for non-unique sched_groups per domain, we need to
carry the cpu_power elsewhere, so put a level of indirection in.
Reported-and-tested-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-qkho2byuhe4482fuknss40ad@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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`make headers_check` complains that
linux-2.6/usr/include/linux/sdla.h:116: userspace cannot reference
function or variable defined in the kernel
this is due to that there is no such a kernel function,
void sdla(void *cfg_info, char *dev, struct frad_conf *conf, int quiet);
I don't know why we have it in a kernel header, so remove it.
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6:
Bluetooth: Fix crash with incoming L2CAP connections
Bluetooth: Fix regression in L2CAP connection procedure
gianfar: rx parser
r6040: only disable RX interrupt if napi_schedule_prep is successful
net: remove NETIF_F_ALL_TX_OFFLOADS
net: sctp: fix checksum marking for outgoing packets
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There is no software fallback implemented for SCTP or FCoE checksumming,
and so it should not be passed on by software devices like bridge or bonding.
For VLAN devices, this is different. First, the driver for underlying device
should be prepared to get offloaded packets even when the feature is disabled
(especially if it advertises it in vlan_features). Second, devices under
VLANs do not get replaced without tearing down the VLAN first.
This fixes a mess I accidentally introduced while converting bonding to
ndo_fix_features.
NETIF_F_SOFT_FEATURES are removed from BOND_VLAN_FEATURES because they
are unused as of commit 712ae51afd.
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
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