The kernel/torture.c module now has several module parameters, so this
commit causes them to be printed out.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The stuttering code isn't functioning as expected. Ideally, it should
pause the torture threads for a designated period before resuming. Yet,
it fails to halt the test for the correct duration. Additionally, a race
condition exists, potentially causing the stuttering code to pause for
an extended period if the 'spt' variable is non-zero due to the stutter
orchestration thread's inadequate CPU time.
Moreover, over-stuttering can hinder RCU's progress on TREE07 kernels.
This happens as the stuttering code may run within a softirq due to RCU
callbacks. Consequently, ksoftirqd keeps a CPU busy for several seconds,
thus obstructing RCU's progress. This situation triggers a warning
message in the logs:
[ 2169.481783] rcu_torture_writer: rtort_pipe_count: 9
This warning suggests that an RCU torture object, although invisible to
RCU readers, couldn't make it past the pipe array and be freed -- a
strong indication that there weren't enough grace periods during the
stutter interval.
To address these issues, this patch sets the "stutter end" time to an
absolute point in the future set by the main stutter thread. This is
then used for waiting in stutter_wait(). While the stutter thread still
defines this absolute time, the waiters' waiting logic doesn't rely on
the stutter thread receiving sufficient CPU time to halt the stuttering
as the halting is now self-controlled.
Cc: stable@vger.kernel.org
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The current torture-test sleeps are waiting for a duration, but there
are situations where it is better to wait for an absolute time, for
example, when ending a stutter interval. This commit therefore adds
an hrtimer mode parameter to torture_hrtimeout_ns(). Why not also the
other torture_hrtimeout_*() functions? The theory is that most absolute
times will be in nanoseconds, especially not (say) jiffies.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Both torture_shuffle_tasks() and its caller torture_shuffle()
define a torture_random_state structure. This is suboptimal given
that torture_shuffle_tasks() runs for a very short period of time.
This commit therefore causes torture_shuffle() to pass a pointer to its
torture_random_state structure down to torture_shuffle_tasks().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Now that torture_random() uses swahw32(), its callers no longer see
not-so-random low-order bits, as these are now swapped up into the upper
16 bits of the torture_random() function's return value. This commit
therefore removes the right-shifting of torture_random() return values.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
In order to gain better race coverage, move the test start/stop
waits in stutter_wait() to torture_hrtimeout_jiffies().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
In order to gain better race coverage, move the CPU-migration timed
waits in torture_shuffle() to torture_hrtimeout_jiffies().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
In order to gain better race coverage, move the CPU-hotplug-related
timed waits in torture_onoff() to torture_hrtimeout_jiffies().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Given that it is expected that more code will use torture_hrtimeout_*(),
including for longer timeouts, make it use TASK_IDLE instead of
TASK_UNINTERRUPTIBLE.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a module parameter that causes the locktorture writer
to run at real-time priority.
To use it:
insmod /lib/modules/torture.ko random_shuffle=1
insmod /lib/modules/locktorture.ko torture_type=mutex_lock rt_boost=1 rt_boost_factor=50 nested_locks=3 writer_fifo=1
^^^^^^^^^^^^^
A predecessor to this patch has been helpful to uncover issues with the
proxy-execution series.
[ paulmck: Remove locktorture-specific code from kernel/torture.c. ]
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: kernel-team@android.com
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
[jstultz: Include header change to build, reword commit message]
Signed-off-by: John Stultz <jstultz@google.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a kthread-creation callback to the
_torture_create_kthread() function, which allows callers of a new
torture_create_kthread_cb() macro to specify a function to be invoked
after the kthread is created but before it is awakened for the first time.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: kernel-team@android.com
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: John Stultz <jstultz@google.com>
Currently shuffling sets the same cpu affinities for all tasks,
which makes us less likely to hit paths involving migrating
blocked tasks onto a cpu where they can't run.
This patch adds an element of randomness to allow affinities of
different writer tasks to diverge.
This has helped uncover issues in testing with Proxy Execution
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: kernel-team@android.com
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
During rcutorture shutdown, the rcu_torture_cleanup() function calls
torture_cleanup_begin(), which sets the fullstop global variable to
FULLSTOP_RMMOD. This causes the rcutorture threads for readers and
fakewriters to exit all of their "while" loops and start shutting down.
They then call torture_kthread_stopping(), which in turn waits for
kthread_stop() to be called. However, rcu_torture_cleanup() has
not yet called kthread_stop() on those threads, and before it gets a
chance to do so, multiple instances of torture_kthread_stopping() invoke
schedule_timeout_interruptible(1) in a tight loop. Tracing confirms that
TIMER_SOFTIRQ can then continuously execute timer callbacks. If that
TIMER_SOFTIRQ preempts the task executing rcu_torture_cleanup(), that
task might never invoke kthread_stop().
This commit improves this situation by increasing the timeout passed to
schedule_timeout_interruptible() from one jiffy to 1/20th of a second.
This change prevents TIMER_SOFTIRQ from monopolizing its CPU, thus
allowing rcu_torture_cleanup() to carry out the needed kthread_stop()
invocations. Testing has shown 100 runs of TREE07 passing reliably,
as oppose to the tens-of-percent failure rates seen beforehand.
Cc: Paul McKenney <paulmck@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc: <stable@vger.kernel.org> # 6.0.x
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The DEFINE_TORTURE_RANDOM_PERCPU() macro defines per-CPU random-number
generators for torture testing, but the seeds for each CPU's instance
will be identical if they are first used at the same time. This commit
therefore adds the CPU number to the mix when reseeding.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, _torture_create_kthread() uses kthread_run() to create
torture-test kthreads, which means that the resulting task_struct
pointer is stored after the newly created kthread has been marked
runnable. This in turn can cause spurious failure of checks for
code being run by a particular kthread. This commit therefore changes
_torture_create_kthread() to use kthread_create(), then to do an explicit
wake_up_process() after the task_struct pointer has been stored.
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Right now, if a given kthread (call it "kthread") realizes that it needs
to stop, "Stopping kthread" is written to the console. When the cleanup
code decides that it is time to stop that kthread, "Stopping kthread
tasks" is written to the console. These two events might happen in
either order, especially in the case of time-based torture-test shutdown.
But it is hard to distinguish these, especially for those unfamiliar with
the torture tests. This commit therefore changes the first case from
"Stopping kthread" to "kthread is stopping" to make things more clear.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Unconditionally log messages corresponding to errors.
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Li Zhijian <zhijianx.li@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The functions get_online_cpus() and put_online_cpus() have been
deprecated during the CPU hotplug rework. They map directly to
cpus_read_lock() and cpus_read_unlock().
Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit replaces a hard-coded "torture_init_begin" string in
a pr_alert() format with "%s" and __func__.
Signed-off-by: Stephen Zhang <stephenzhangzsd@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The TREE01 rcutorture scenario intentionally creates confusion as to the
number of available CPUs by specifying the "maxcpus=8 nr_cpus=43" kernel
boot parameters. This can disable rcutorture's load shedding, which
currently uses num_online_cpus(), which would count the extra 35 CPUs.
However, the rcutorture guest OS will be provisioned with only 8 CPUs,
which means that rcutorture will present full load even when all but one
of the original 8 CPUs are offline. This can result in spurious errors
due to extreme overloading of that single remaining CPU.
This commit therefore keeps a separate set of books on the number of
usable online CPUs, so that torture_num_online_cpus() is used for load
shedding instead of num_online_cpus(). Note that initial sizing must
use num_online_cpus() because torture_num_online_cpus() will return
NR_CPUS until shortly after torture_onoff_init() is invoked.
Reported-by: Frederic Weisbecker <frederic@kernel.org>
[ paulmck: Apply feedback from kernel test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit puts all CPUs back online at the end of a torture test,
and also unconditionally puts them online at the beginning of the test,
rather than just in the case of built-in tests. This allows torture tests
to behave in a predictable manner, whether built-in or based on modules.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds kernel boot parameters torture.verbose_sleep_frequency
and torture.verbose_sleep_duration, which allow VERBOSE_TOROUT_*() output
to be throttled with periodic sleeps on large systems.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit saves a few lines of code by making the stutter_wait()
and torture_stutter() functions use torture_hrtimeout_jiffies() and
torture_hrtimeout_us().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds torture_hrtimeout_ns(), torture_hrtimeout_us(),
torture_hrtimeout_ms(), torture_hrtimeout_jiffies(), and
torture_hrtimeout_s(), each of which uses hrtimers to block for a fuzzed
time interval. These functions are intended to be used by the various
torture tests to decouple wakeups from the timer wheel, thus providing
more opportunity for Murphy to insert destructive race conditions.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, stutter_wait() will happily spin waiting for the stutter
interval to end even if the caller is running at a real-time priority
level. This could starve normal-priority tasks for no good reason. This
commit therefore drops the calling task's priority to SCHED_OTHER MAX_NICE
if stutter_wait() needs to wait. But when it waits, stutter_wait()
returns true, which allows the caller to restore the priority if needed.
Callers that were already running at SCHED_OTHER MAX_NICE obviously
do not need any changes, but this commit also restores priority for
higher-priority callers.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The torture_stutter() function uses schedule_timeout_interruptible()
to time the stutter duration, but this can miss race conditions due to
its being time-synchronized with everything else that is based on the
timer wheels. This commit therefore converts torture_stutter() to use
the high-resolution timers via schedule_hrtimeout(), and also to fuzz
the stutter interval. While in the area, this commit also limits the
spin-loop portion of the stutter_wait() function's wait loop to two
jiffies, down from about one second.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Running locktorture scenario LOCK05 results in hangs:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --torture lock --duration 3 --configs LOCK05
The lock_torture_writer() kthreads set themselves to MAX_NICE while
running SCHED_OTHER. Other locktorture kthreads run at default niceness,
also SCHED_OTHER. This results in these other locktorture kthreads
indefinitely preempting the lock_torture_writer() kthreads. Note that
the cond_resched() in the stutter_wait() function's loop is ineffective
because this scenario is built with CONFIG_PREEMPT=y.
It is not clear that such indefinite preemption is supposed to happen, but
in the meantime this commit prevents kthreads running in stutter_wait()
from being completely CPU-bound, thus allowing the other threads to get
some CPU in a timely fashion. This commit also uses hrtimers to provide
very short sleeps to avoid degrading the sudden-on testing that stutter
is supposed to provide.
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If there is a large number of torture tests running concurrently,
all of which are dumping large ftrace buffers at shutdown time, the
resulting dumping can take a very long time, particularly on systems
with rotating-rust storage. This commit therefore adds a default-off
torture.ftrace_dump_at_shutdown module parameter that enables
shutdown-time ftrace-buffer dumping.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
- Support for locked CSD objects in smp_call_function_single_async()
which allows to simplify callsites in the scheduler core and MIPS
- Treewide consolidation of CPU hotplug functions which ensures the
consistency between the sysfs interface and kernel state. The low level
functions cpu_up/down() are now confined to the core code and not
longer accessible from random code.
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Merge tag 'smp-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core SMP updates from Thomas Gleixner:
"CPU (hotplug) updates:
- Support for locked CSD objects in smp_call_function_single_async()
which allows to simplify callsites in the scheduler core and MIPS
- Treewide consolidation of CPU hotplug functions which ensures the
consistency between the sysfs interface and kernel state. The low
level functions cpu_up/down() are now confined to the core code and
not longer accessible from random code"
* tag 'smp-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
cpu/hotplug: Ignore pm_wakeup_pending() for disable_nonboot_cpus()
cpu/hotplug: Hide cpu_up/down()
cpu/hotplug: Move bringup of secondary CPUs out of smp_init()
torture: Replace cpu_up/down() with add/remove_cpu()
firmware: psci: Replace cpu_up/down() with add/remove_cpu()
xen/cpuhotplug: Replace cpu_up/down() with device_online/offline()
parisc: Replace cpu_up/down() with add/remove_cpu()
sparc: Replace cpu_up/down() with add/remove_cpu()
powerpc: Replace cpu_up/down() with add/remove_cpu()
x86/smp: Replace cpu_up/down() with add/remove_cpu()
arm64: hibernate: Use bringup_hibernate_cpu()
cpu/hotplug: Provide bringup_hibernate_cpu()
arm64: Use reboot_cpu instead of hardconding it to 0
arm64: Don't use disable_nonboot_cpus()
ARM: Use reboot_cpu instead of hardcoding it to 0
ARM: Don't use disable_nonboot_cpus()
ia64: Replace cpu_down() with smp_shutdown_nonboot_cpus()
cpu/hotplug: Create a new function to shutdown nonboot cpus
cpu/hotplug: Add new {add,remove}_cpu() functions
sched/core: Remove rq.hrtick_csd_pending
...
The core device API performs extra housekeeping bits that are missing
from directly calling cpu_up/down().
See commit a6717c01dd ("powerpc/rtas: use device model APIs and
serialization during LPM") for an example description of what might go
wrong.
This also prepares to make cpu_up/down() a private interface of the CPU
subsystem.
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: "Paul E. McKenney" <paulmck@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-16-qais.yousef@arm.com
In theory, RCU-hotplug operations are supposed to work as soon as there
is more than one CPU online. However, in practice, in normal production
there is no way to make them happen until userspace is up and running.
Besides which, on smaller systems, rcutorture doesn't start doing hotplug
operations until 30 seconds after the start of boot, which on most
systems also means the better part of 30 seconds after the end of boot.
This commit therefore provides a new torture.disable_onoff_at_boot kernel
boot parameter that suppresses CPU-hotplug torture operations until
about the time that init is spawned.
Of course, if you know of a need for boottime CPU-hotplug operations,
then you should avoid passing this argument to any of the torture tests.
You might also want to look at the splats linked to below.
Link: https://lore.kernel.org/lkml/20191206185208.GA25636@paulmck-ThinkPad-P72/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
During boot, CPU hotplug is often disabled, for example by PCI probing.
On large systems that take substantial time to boot, this can result
in spurious RCU_HOTPLUG errors. This commit therefore forgives any
boottime -EBUSY CPU-hotplug failures by adjusting counters to pretend
that the corresponding attempt never happened. A non-splat record
of the failed attempt is emitted to the console with the added string
"(-EBUSY forgiven during boot)".
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The functions torture_onoff_cleanup() and torture_shuffle_cleanup()
are declared static and marked EXPORT_SYMBOL_GPL(), which is at best an
odd combination. Because these functions are not used outside of the
kernel/torture.c file they are defined in, this commit removes their
EXPORT_SYMBOL_GPL() marking.
Fixes: cc47ae0830 ("rcutorture: Abstract torture-test cleanup")
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Currently, the inter-stutter interval is the same as the stutter duration,
that is, whatever number of jiffies is passed into torture_stutter_init().
This has worked well for quite some time, but the addition of
forward-progress testing to rcutorture can delay processes for several
seconds, which can triple the time that they are stuttered.
This commit therefore adds a second argument to torture_stutter_init()
that specifies the inter-stutter interval. While locktorture preserves
the current behavior, rcutorture uses the RCU CPU stall warning interval
to provide a wider inter-stutter interval.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
The stutter_wait() function is supposed to return true if it actually
waits and false otherwise, but it instead unconditionally returns false.
Which hides a bug in rcu_torture_writer() that fails to account for
the fact that one of the rcu_tortures[] array elements will normally be
referenced by rcu_torture_current, and thus not be on the freelist.
This commit therefore corrects the stutter_wait() return value and adds a
check for rcu_torture_current to rcu_torture_writer()'s check that things
get freed after everything goes quiescent. In addition, this commit
causes torture_stutter() to give a bit more than one second (instead of
only one jiffy) warning of the end of the stutter interval. Finally,
this commit disables long-delay readers and aggressive update-side
forward-progress checks while forward-progress testing is in flight.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
If there is only one online CPU, it doesn't make sense to try to offline
it, as any such attempt is guaranteed to fail. This commit therefore
check for this condition and refuses to attempt the nonsensical.
Reported-by: Su Yue <suy.fnst@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tested-By: Su Yue <suy.fnst@cn.fujitsu.com>
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Beyond a certain point in the CPU-hotplug offline process, timers get
stranded on the outgoing CPU, and won't fire until that CPU comes back
online, which might well be never. This commit therefore adds a hook
in torture_onoff_init() that is invoked from torture_offline(), which
rcutorture uses to occasionally wait for a grace period. This should
result in failures for RCU implementations that rely on stranded timers
eventually firing in the absence of the CPU coming back online.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Remove return variables (declared as "ret") in cases where,
depending on whether a condition evaluates as true, the result of a
function call can be immediately returned instead of storing the result in
the return variable. When the condition evaluates as false, the constant
initially stored in the return variable at declaration is returned instead.
Signed-off-by: Pierce Griffiths <pierceagriffiths@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Currently, the torture scripts rely on the initrd/init script to bring
any extra CPUs online, for example, in the case where the kernel and
qemu have different ideas about how many CPUs are present. This works,
but is an unnecessary dependency on initrd, which needs to vary depending
on the distro. This commit therefore causes torture_onoff() to check
for additional CPUs, attempting to bring any found online. Errors are
ignored, just as they are by the initrd/init script.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The rcu_torture_writer() function invokes stutter_wait() at the end of
each writer pass, which occasionally blocks for an extended time period
in order to ensure that RCU can handle intermittent loads. But part of
handling a busy period is invoking all the callbacks before the end of
the idle period induced by stutter_wait().
This commit therefore adds a return value to stutter_wait() indicating
whether stutter_wait() actually waited. In addition, this commit causes
rcu_torture_writer() to test this value and if set, checks that all the
elements of the rcu_tortures[] array have been freed up.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit adds "#define pr_fmt(fmt) fmt" to the torture-test files
in order to keep the current dmesg format. Once Joe's commits have
hit mainline, these definitions will be changed in order to automatically
generate the dmesg line prefix that the scripts expect. This will have
the beneficial side-effect of allowing printk() formats to be used more
widely and of shortening some pr_*() lines.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Joe Perches <joe@perches.com>
Some bugs reproduce quickly only at high CPU-hotplug rates, so the
rcutorture TREE03 scenario now has only 200 milliseconds spacing between
CPU-hotplug operations. At this rate, the torture-test pair of console
messages per operation becomes a bit voluminous. This commit therefore
converts the torture-test set of "verbose" kernel-boot arguments from
bool to int, and prints the extra console messages only when verbose=2.
The default is still verbose=1.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Commit e31d28b6ab ("trace: Eliminate cond_resched_rcu_qs() in favor
of cond_resched()") substituted cond_resched() for the earlier call
to cond_resched_rcu_qs(). However, the new-age cond_resched() does
not do anything to help RCU-tasks grace periods because (1) RCU-tasks
is only enabled when CONFIG_PREEMPT=y and (2) cond_resched() is a
complete no-op when preemption is enabled. This situation results
in hangs when running the trace benchmarks.
A number of potential fixes were discussed on LKML
(https://lkml.kernel.org/r/20180224151240.0d63a059@vmware.local.home),
including making cond_resched() not be a no-op; making cond_resched()
not be a no-op, but only when running tracing benchmarks; reverting
the aforementioned commit (which works because cond_resched_rcu_qs()
does provide an RCU-tasks quiescent state; and adding a call to the
scheduler/RCU rcu_note_voluntary_context_switch() function. All were
deemed unsatisfactory, either due to added cond_resched() overhead or
due to magic functions inviting cargo culting.
This commit renames cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs(),
which provides a clear hint as to what this function is doing and
why and where it should be used, and then replaces the call to
cond_resched() with cond_resched_tasks_rcu_qs() in the trace benchmark's
benchmark_event_kthread() function.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
The purpose of torture_runnable is to allow rcutorture and locktorture
to be started and stopped via sysfs when they are built into the kernel
(as in not compiled as loadable modules). However, the 0444 permissions
for both instances of torture_runnable prevent this use case from ever
being put into practice. Given that there have been no complaints
about this deficiency, it is reasonable to conclude that no one actually
makes use of this sysfs capability. The perf_runnable module parameter
for rcuperf is in the same situation.
This commit therefore removes both torture_runnable instances as well
as perf_runnable.
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The stutter_wait() function repeatedly fetched stutter_pause_test, and
should really just fetch it once on each pass. The races should be
harmless, but why have the races? Also, the whole point of the value
"2" for stutter_pause_test is to get everyone to start at very nearly
the same time, but the value "2" was the first jiffy of the stutter
rather than the last jiffy of the stutter.
This commit rearranges the code to be more sensible.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The torture_shutdown() function directly invokes ftrace_dump(), which
can result in RCU CPU stall warnings when the ftrace buffer is large,
which it usually is. This commit therefore invoks rcu_ftrace_dump()
in place of ftrace_dump(), suppressing RCU CPU stall warnings during
this time.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The torture status line contains a series of values preceded by "onoff:".
The last value in that line, the one preceding the "HZ=" string, is
always zero. The reason that it is always zero is that torture_offline()
was incrementing the sum_offl pointer instead of the value that this
pointer referenced. This commit therefore makes this increment operate
on the statistic rather than the pointer to the statistic.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney