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Now that CONFIG_PREEMPT_DYNAMIC=y is the default, kernels that are
ostensibly built with CONFIG_PREEMPT_NONE=y or CONFIG_PREEMPT_VOLUNTARY=y
are now actually built with CONFIG_PREEMPT=y, but are by default booted
so as to disable preemption. Although this allows much more flexibility
from a single kernel binary, it means that the current rcutorture
scenarios won't find build errors that happen only when preemption is
fully disabled at build time.
This commit therefore adds CONFIG_PREEMPT_DYNAMIC=n to several scenarios,
and while in the area switches one from CONFIG_PREEMPT_NONE=y to
CONFIG_PREEMPT_VOLUNTARY=y to add coverage of this Kconfig option.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcutorture test suite makes double use of the rcutorture.stat_interval
module parameter. As its name suggests, it controls the frequency
of statistics printing, but it also controls the rcu_torture_writer()
stall timeout. The current setting of 15 seconds works surprisingly well.
However, given that the RCU tasks stall-warning timeout is ten -minutes-,
15 seconds is too short for TASKS02, which runs a non-preemptible kernel
on a single CPU.
This commit therefore adds checks for per-scenario specification of the
rcutorture.stat_interval module parameter.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Now that CONFIG_PREEMPT_DYNAMIC=y is the default, TASKS02 no longer
builds a pure non-preemptible kernel that uses Tiny RCU. This commit
therefore fixes this new hole in rcutorture testing by adding
CONFIG_PREEMPT_DYNAMIC=n to the TASKS02 rcutorture scenario.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Unless a kernel builds rcutorture, whether built-in or as a module, that
kernel is also built with CONFIG_TASKS_RUDE_RCU, whether anything else
needs Tasks Rude RCU or not. This unnecessarily increases kernel size.
This commit therefore decouples the presence of rcutorture from the
presence of RCU Tasks Rude.
However, there is a need to select CONFIG_TASKS_RUDE_RCU for testing
purposes. Except that casual users must not be bothered with
questions -- for them, this needs to be fully automated. There is
thus a CONFIG_FORCE_TASKS_RUDE_RCU that selects CONFIG_TASKS_RUDE_RCU,
is user-selectable, but which depends on CONFIG_RCU_EXPERT.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks. Unless that kernel builds rcutorture, whether built-in or as
a module, in which case RCU Tasks is (unnecessarily) used. This both
increases kernel size and increases the complexity of certain tracing
operations. This commit therefore decouples the presence of rcutorture
from the presence of RCU Tasks.
However, there is a need to select CONFIG_TASKS_RCU for testing purposes.
Except that casual users must not be bothered with questions -- for them,
this needs to be fully automated. There is thus a CONFIG_FORCE_TASKS_RCU
that selects CONFIG_TASKS_RCU, is user-selectable, but which depends
on CONFIG_RCU_EXPERT.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Unless a kernel builds rcutorture, whether built-in or as a module, that
kernel is also built with CONFIG_TASKS_TRACE_RCU, whether anything else
needs Tasks Trace RCU or not. This unnecessarily increases kernel size.
This commit therefore decouples the presence of rcutorture from the
presence of RCU Tasks Trace.
However, there is a need to select CONFIG_TASKS_TRACE_RCU for
testing purposes. Except that casual users must not be bothered with
questions -- for them, this needs to be fully automated. There is thus
a CONFIG_FORCE_TASKS_TRACE_RCU that selects CONFIG_TASKS_TRACE_RCU,
is user-selectable, but which depends on CONFIG_RCU_EXPERT.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, any kernel built with CONFIG_PREEMPTION=y also gets
CONFIG_TASKS_RCU=y, which is not helpful to people trying to build
preemptible kernels of minimal size.
Because CONFIG_TASKS_RCU=y is needed only in kernels doing tracing of
one form or another, this commit moves from TASKS_RCU deciding when it
should be enabled to the tracing Kconfig options explicitly selecting it.
This allows building preemptible kernels without TASKS_RCU, if desired.
This commit also updates the SRCU-N and TREE09 rcutorture scenarios
in order to avoid Kconfig errors that would otherwise result from
CONFIG_TASKS_RCU being selected without its CONFIG_RCU_EXPERT dependency
being met.
[ paulmck: Apply BPF_SYSCALL feedback from Andrii Nakryiko. ]
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adjusts RUDE01 to 3 CPUs and TRACE01 to 5 CPUs in order to
test Tasks RCU's ability to handle non-power-of-two numbers of CPUs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Thie commit adds kernel boot parameters to the SRCU-N and SRCU-P
rcutorture scenarios to cause SRCU-N to test contention-based resizing
and SRCU-P to test init_srcu_struct()-time resizing. Note that this
also tests never-resizing because the contention-based resizing normally
takes some minutes to make the shift.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit modifies the TASKS01 scenario to use four callback queues
and the TRACE01 scenario to use two queues, thus providing testing of
multiple queues by default.
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adjusts the TRACE02 scenario to use a pair of callback-flood
kthreads. This in turn forces lock contention on the single RCU Tasks
Trace callback queue, which forces use of all CPUs' queues, thus testing
this transition. (No, there is not yet any way to transition back.
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit enables two callback-flood kthreads for the TREE02 scenario
and 28 for the TREE10 scenario.
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
All of the uses of CONFIG_RCU_FAST_NO_HZ=y that I have seen involve
systems with RCU callbacks offloaded. In this situation, all that this
Kconfig option does is slow down idle entry/exit with an additional
allways-taken early exit. If this is the only use case, then this
Kconfig option nothing but an attractive nuisance that needs to go away.
This commit therefore removes the RCU_FAST_NO_HZ Kconfig option.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
All of the rcu scenarios that mentioning CONFIG_RCU_FAST_NO_HZ disable it.
But this Kconfig option is disabled by default, so this commit removes
the pointless "CONFIG_RCU_FAST_NO_HZ=n" lines from these scenarios.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
With CONFIG_PREEMPT_DYNAMIC=y, the kernel builds with CONFIG_PREEMPTION=y
because preemption can be enabled at runtime. This prevents any tests
of Tiny RCU or Tiny SRCU from running correctly. This commit therefore
explicitly sets CONFIG_PREEMPT_DYNAMIC=n for those scenarios.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is no way to place the vCPUs in a two-CPU rcutorture scenario to
get variable memory latency. This commit therefore upgrades the current
two-CPU rcutorture scenarios to four CPUs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the BUSTED-BOOST rcutorture scenario, which can be
used to test rcutorture's ability to test RCU priority boosting.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The convention that scenario names are all uppercase has two exceptions,
SRCU-t and SRCU-u. This commit therefore renames them to SRCU-T and
SRCU-U, respectively, to bring them in line with this convention. This in
turn permits tighter argument checking in the torture-test scripting.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
TREE03 tests RCU priority boosting, which is a real-time feature.
It would also be good if it tested something closer to what is
actually used by the real-time folks. This commit therefore adds
tree.use_softirq=0 to the TREE03 kernel boot parameters in TREE03.boot.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit uses the shiny new "all" and "N" cpumask options to decouple
the "nohz_full" and "rcu_nocbs" kernel boot parameters in the TREE04.boot
and TREE08.boot files from the CONFIG_NR_CPUS options in the TREE04 and
TREE08 files.
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
RCU's rcutree.use_softirq=0 kernel boot parameter substitutes the per-CPU
rcuc kthreads for softirq, which is used in real-time installations.
However, none of the rcutorture scenarios test this parameter.
This commit therefore adds rcutree.use_softirq=0 to the RUDE01 and
TASKS01 rcutorture scenarios, both of which indirectly exercise RCU.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds periodic toggling of 7 of 8 CPUs every second to TREE01
in order to test NOCB toggle code.
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The SRCU-u scenario expects to enable lockdep but to also disable the
CONFIG_PREEMPT_COUNT kconfig option. This no longer works. This commit
therefore instead enables lockdep in SRCU-t, which then allows SRCU-u
to disable CONFIG_PREEMPT_COUNT.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, the CONFIG_PREEMPT_NONE=y rcutorture TRACE01 rcutorture
scenario enables lockdep. This limits its ability to find bugs due to
non-preemptible sections of code being RCU readers, and pretty much all
code thus appearing to lockdep to be an RCU reader. This commit therefore
moves lockdep testing to the CONFIG_PREEMPT=y rcutorture TRACE02 scenario.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, the CONFIG_PROVE_RCU_LIST=y case is untested. This commit
therefore adds CONFIG_PROVE_RCU_LIST=y to rcutorture's TREE05 scenario.
Cc: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
fixes.2020.04.27a: Miscellaneous fixes.
kfree_rcu.2020.04.27a: Changes related to kfree_rcu().
rcu-tasks.2020.04.27a: Addition of new RCU-tasks flavors.
stall.2020.04.27a: RCU CPU stall-warning updates.
torture.2020.05.07a: Torture-test updates.
The number of CPUs is tuned to allow "4*CFLIST TREE10" on a large system,
up from "3*CFLIST TREE10" previously.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a TRACE02 scenario which enables preemption and RCU
Tasks Trace IPIs, more specifically, disabling heavyweight readers.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit enables the KCSAN Kconfig options that (1) detect data
races between reads and writes even when the writes do not change the
variable's value and (2) detect data races involving plain C-language
writes. These changes only affect scripted rcutorture runs and can be
overridden using the kvm.sh --kconfig argument.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The small-system rcutorture configurations have served us well for a great
many years, but it is now time to add a larger one. This commit does
just that, but does not add it to the defaults in CFLIST. This allows
the kvm.sh argument '--configs "4*CFLIST TREE10" to run four instances
of each of the default configurations concurrently with one instance of
the large configuration.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
A number of mainstream CPU families are no longer capable of building
kernels having CONFIG_SMP=y and CONFIG_HOTPLUG_CPU=n, so this commit
removes this combination from the rcutorture scenarios having it.
People wishing to try out this combination may still do so using the
"--kconfig CONFIG_HOTPLUG_CPU=n CONFIG_SUSPEND=n CONFIG_HIBERNATION=n"
argument to the tools/testing/selftests/rcutorture/bin/kvm.sh script
that is used to run rcutorture.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Since commit 05f415715c ("rcu: Speed up expedited GPs when interrupting
RCU reader") in v5.0 and through v5.1, booting with the threadirqs kernel
boot parameter caused self-deadlocks, which can be reproduced using the
following command on an 8-CPU system:
tools/testing/selftests/rcutorture/bin/kvm.sh --duration 5 --configs "TREE03" --bootargs "threadirqs"
This commit therefore adds the threadirqs kernel boot parameter to
the TREE03 rcutorture scenario in order to more quickly detect future
similar bugs.
Link: http://lkml.kernel.org/r/20190626135447.y24mvfuid5fifwjc@linutronix.de
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Joel Fernandes <joel@joelfernandes.org>
In one of my rcutorture tests the TSC clocksource got marked unstable
due to a large difference in the TSC value. I'm not sure if the guest
run for a long time with disabled interrupts or if the host was very
busy and didn't schedule the guest for some time.
I took a look on the qemu/KVM options and decided to update the options:
- Use kvm{32|64} as CPU. We could probably use `host' (like ARM does)
for maximum available features but since we don't run any userland I'm
not sure if it makes any difference.
- Drop the "noapic" option. There is no history why the APIC was disabled,
I see no reason for it. Once old qemu versions fade away, we can add
"x2apic=on,tsc-deadline=on,hypervisor=on,tsc_adjust=on".
- Additional config options. It ensures that the kernel knowns that it
runs as a kvm guest and can use virt devices like the kvm-clock as
clocksource. The kvm-clock was the main motivation here.
- I didn't add a random HW device. It would make the random device ready
earlier (not it doesn't complete the initialisation at all) but I
doubt that there is any need for this.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ paulmck: The world is not quite ready for CONFIG_PARAVIRT_SPINLOCKS=y
and x2apic, so they are omitted for the time being. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
I have been showing off a trivial RCU implementation for non-preemptive
environments for some time now:
#define rcu_read_lock()
#define rcu_read_unlock()
#define rcu_dereference(p) READ_ONCE(p)
#define rcu_assign_pointer(p, v) smp_store_release(&(p), (v))
void synchronize_rcu(void)
{
int cpu;
for_each_online_cpu(cpu)
sched_setaffinity(current->pid, cpumask_of(cpu));
}
Trivial or not, as the old saying goes, "if it ain't tested, it don't
work!". This commit therefore adds a "trivial" flavor to rcutorture
and a corresponding TRIVIAL test scenario. This variant does not handle
CPU hotplug, which is unconditionally enabled on x86 for post-v5.1-rc3
kernels, which is why the TRIVIAL.boot says "rcutorture.onoff_interval=0".
This commit actually does handle CONFIG_PREEMPT=y kernels, but only
because it turns back the Linux-kernel clock in order to provide these
alternative definitions (or the moral equivalent thereof):
#define rcu_read_lock() preempt_disable()
#define rcu_read_unlock() preempt_enable()
In CONFIG_PREEMPT=n kernels without debugging, these are equivalent to
empty macros give or take a compiler barrier. However, the have been
successfully tested with actual empty macros as well.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Fix symbol issue reported by kbuild test robot <lkp@intel.com>. ]
[ paulmck: Work around sched_setaffinity() issue noted by Andrea Parri. ]
[ paulmck: Add rcutorture.shuffle_interval=0 to TRIVIAL.boot to fix
interaction with shuffler task noted by Peter Zijlstra. ]
Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Because TREE01 can end up running more vCPUs that physical CPUs,
hammering these shortchanged CPUs with tight loops containing call_rcu()
invocations seems a bit like overkill. This commit therefore exempts
TREE01 from rcutorture's forward-progress testing.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address and add copyright notices.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Now that SRCU permits call_srcu() to be invoked at early boot, this
commit ensures that the rcutorture scripting tests early boot call_srcu().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Now that the RCU-bh and RCU-sched update-side functions are simple
wrappers around their RCU counterparts, there isn't a whole lot of
point in testing them. This commit therefore removes the self-test
capability and removes the corresponding kernel-boot parameters.
It also updates the various rcutorture .boot files to remove the
kernel boot parameters that call for testing RCU-bh and RCU-sched.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Now that there is only one RCU flavor to rule them all, the TREE06
and TREE08 test scenarios are redundant. This commit therefore removes
them. Later changes will rebalance and renumber the tests.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Some RCU bugs have been sensitive to the frequency of CPU-hotplug
operations, which have been gradually increased over time. But this
frequency is now at the one-second lower limit that can be specified using
the rcutorture.onoff_interval kernel parameter. This commit therefore
changes the units of rcutorture.onoff_interval from seconds to jiffies,
and also sets the value specified for this kernel parameter in the TREE03
rcutorture scenario to 200, which is 200 milliseconds for HZ=1000.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The main race with the early part of grace-period initialization appears
to be with CPU hotplug. To more fully open this race window, this commit
moves the rcu_gp_slow() from the beginning of the early initialization
loop to follow that loop, thus widening the race window, especially for
the rcu_node structures that are initialized last. This commit also
expands rcutree.gp_preinit_delay from 3 to 12, giving the same overall
delay in the grace period, but concentrated in the spot where it will
do the most good.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The TREE08-T.boot file was used to provide alternative options for
debugging, but things have changed, it has not kept up, and it has not
been used or missed. This commit therefore removes it.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
