rcu: Rename jiffies_till_flush to jiffies_lazy_flush

The variable name jiffies_till_flush is too generic and therefore:

* It may shadow a global variable
* It doesn't tell on what it operates

Make the name more precise, along with the related APIs.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

rcuscale: Move rcu_scale_writer() schedule_timeout_uninterruptible() to _idle()

The rcuscale.holdoff module parameter can be used to delay the start
of rcu_scale_writer() kthread. However, the hung-task timeout will
trigger when the timeout specified by rcuscale.holdoff is greater than
hung_task_timeout_secs:

runqemu kvm nographic slirp qemuparams="-smp 4 -m 2048M"
bootparams="rcuscale.shutdown=0 rcuscale.holdoff=300"

[ 247.071753] INFO: task rcu_scale_write:59 blocked for more than 122 seconds.
[ 247.072529] Not tainted 6.4.0-rc1-00134-gb9ed6de8d4ff #7
[ 247.073400] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 247.074331] task:rcu_scale_write state:D stack:30144 pid:59 ppid:2 flags:0x00004000
[ 247.075346] Call Trace:
[ 247.075660] <TASK>
[ 247.075965] __schedule+0x635/0x1280
[ 247.076448] ? __pfx___schedule+0x10/0x10
[ 247.076967] ? schedule_timeout+0x2dc/0x4d0
[ 247.077471] ? __pfx_lock_release+0x10/0x10
[ 247.078018] ? enqueue_timer+0xe2/0x220
[ 247.078522] schedule+0x84/0x120
[ 247.078957] schedule_timeout+0x2e1/0x4d0
[ 247.079447] ? __pfx_schedule_timeout+0x10/0x10
[ 247.080032] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.080591] ? __pfx_process_timeout+0x10/0x10
[ 247.081163] ? __pfx_sched_set_fifo_low+0x10/0x10
[ 247.081760] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.082287] rcu_scale_writer+0x6b1/0x7f0
[ 247.082773] ? mark_held_locks+0x29/0xa0
[ 247.083252] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.083865] ? __pfx_rcu_scale_writer+0x10/0x10
[ 247.084412] kthread+0x179/0x1c0
[ 247.084759] ? __pfx_kthread+0x10/0x10
[ 247.085098] ret_from_fork+0x2c/0x50
[ 247.085433] </TASK>

This commit therefore replaces schedule_timeout_uninterruptible() with
schedule_timeout_idle().

Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: fix building with RCU_TINY

Both the CONFIG_TASKS_RCU and CONFIG_TASKS_RUDE_RCU options
are broken when RCU_TINY is enabled as well, as some functions
are missing a declaration.

In file included from kernel/rcu/update.c:649:
kernel/rcu/tasks.h:1271:21: error: no previous prototype for 'get_rcu_tasks_rude_gp_kthread' [-Werror=missing-prototypes]
1271 | struct task_struct *get_rcu_tasks_rude_gp_kthread(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/rcu/rcuscale.c:330:27: error: 'get_rcu_tasks_rude_gp_kthread' undeclared here (not in a function); did you mean 'get_rcu_tasks_trace_gp_kthread'?
330 | .rso_gp_kthread = get_rcu_tasks_rude_gp_kthread,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| get_rcu_tasks_trace_gp_kthread

In file included from /home/arnd/arm-soc/kernel/rcu/update.c:649:
kernel/rcu/tasks.h:1113:21: error: no previous prototype for 'get_rcu_tasks_gp_kthread' [-Werror=missing-prototypes]
1113 | struct task_struct *get_rcu_tasks_gp_kthread(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~

Also, building with CONFIG_TASKS_RUDE_RCU but not CONFIG_TASKS_RCU is
broken because of some missing stub functions:

kernel/rcu/rcuscale.c:322:27: error: 'tasks_scale_read_lock' undeclared here (not in a function); did you mean 'srcu_scale_read_lock'?
322 | .readlock = tasks_scale_read_lock,
| ^~~~~~~~~~~~~~~~~~~~~
| srcu_scale_read_lock
kernel/rcu/rcuscale.c:323:27: error: 'tasks_scale_read_unlock' undeclared here (not in a function); did you mean 'srcu_scale_read_unlock'?
323 | .readunlock = tasks_scale_read_unlock,
| ^~~~~~~~~~~~~~~~~~~~~~~
| srcu_scale_read_unlock

Move the declarations outside of the RCU_TINY #ifdef and duplicate the
shared stub functions to address all of the above.

Fixes: 88d7ff818f0ce ("rcuscale: Add RCU Tasks Rude testing")
Fixes: 755f1c5eb416b ("rcuscale: Measure RCU Tasks Trace grace-period kthread CPU time")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Add RCU Tasks Rude testing

Add a "tasks-rude" option to the rcuscale.scale_type module parameter.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Measure RCU Tasks Trace grace-period kthread CPU time

This commit causes RCU Tasks Trace to output the CPU time consumed by
its grace-period kthread. The CPU time is whatever is in the designated
task's current->stime field, and thus is controlled by whatever CPU-time
accounting scheme is in effect.

This output appears in microseconds as follows on the console:

rcu_scale: Grace-period kthread CPU time: 42367.037

[ paulmck: Apply Willy Tarreau feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Measure grace-period kthread CPU time

This commit adds the ability to output the CPU time consumed by the
grace-period kthread for the RCU variant under test. The CPU time is
whatever is in the designated task's current->stime field, and thus is
controlled by whatever CPU-time accounting scheme is in effect.

This output appears in microseconds as follows on the console:

rcu_scale: Grace-period kthread CPU time: 42367.037

[ paulmck: Apply feedback from Stephen Rothwell and kernel test robot. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>

rcuscale: Print out full set of kfree_rcu parameters

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>

rcuscale: Print out full set of module parameters

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Add minruntime module parameter

By default, rcuscale collects only 100 points of data per writer, but
arranging for all kthreads to be actively collecting (if not recording)
data during the time that any kthread might be recording. This works
well, but does not allow much time to bring external performance tools
to bear. This commit therefore adds a minruntime module parameter
that specifies a minimum data-collection interval in seconds.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Fix gp_async_max typo: s/reader/writer/

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Permit blocking delays between writers

Some workloads do isolated RCU work, and this can affect operation
latencies. This commit therefore adds a writer_holdoff_jiffies module
parameter that causes writers to block for the specified number of
jiffies between each pair of consecutive write-side operations.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcu/rcuscale: Stop kfree_scale_thread thread(s) after unloading rcuscale

Running the 'kfree_rcu_test' test case [1] results in a splat [2].
The root cause is the kfree_scale_thread thread(s) continue running
after unloading the rcuscale module. This commit fixes that isue by
invoking kfree_scale_cleanup() from rcu_scale_cleanup() when removing
the rcuscale module.

[1] modprobe rcuscale kfree_rcu_test=1
// After some time
rmmod rcuscale
rmmod torture

[2] BUG: unable to handle page fault for address: ffffffffc0601a87
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 11de4f067 P4D 11de4f067 PUD 11de51067 PMD 112f4d067 PTE 0
Oops: 0010 [#1] PREEMPT SMP NOPTI
CPU: 1 PID: 1798 Comm: kfree_scale_thr Not tainted 6.3.0-rc1-rcu+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
RIP: 0010:0xffffffffc0601a87
Code: Unable to access opcode bytes at 0xffffffffc0601a5d.
RSP: 0018:ffffb25bc2e57e18 EFLAGS: 00010297
RAX: 0000000000000000 RBX: ffffffffc061f0b6 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff962fd0de RDI: ffffffff962fd0de
RBP: ffffb25bc2e57ea8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 000000000000000a R15: 00000000001c1dbe
FS: 0000000000000000(0000) GS:ffff921fa2200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffc0601a5d CR3: 000000011de4c006 CR4: 0000000000370ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
? kvfree_call_rcu+0xf0/0x3a0
? kthread+0xf3/0x120
? kthread_complete_and_exit+0x20/0x20
? ret_from_fork+0x1f/0x30
</TASK>
Modules linked in: rfkill sunrpc ... [last unloaded: torture]
CR2: ffffffffc0601a87
---[ end trace 0000000000000000 ]---

Fixes: e6e78b004fa7 ("rcuperf: Add kfree_rcu() performance Tests")
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcu/rcuscale: Move rcu_scale_*() after kfree_scale_cleanup()

This code-movement-only commit moves the rcu_scale_cleanup() and
rcu_scale_shutdown() functions to follow kfree_scale_cleanup().
This is code movement is in preparation for a bug-fix patch that invokes
kfree_scale_cleanup() from rcu_scale_cleanup().

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

rcuscale: Rename kfree_rcu() to kfree_rcu_mightsleep()

The kfree_rcu() and kvfree_rcu() macros' single-argument forms are
deprecated. Therefore switch to the new kfree_rcu_mightsleep() and
kvfree_rcu_mightsleep() variants. The goal is to avoid accidental use
of the single-argument forms, which can introduce functionality bugs in
atomic contexts and latency bugs in non-atomic contexts.

Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

rcuscale: Move shutdown from wait_event() to wait_event_idle()

The rcu_scale_shutdown() and kfree_scale_shutdown() kthreads/functions
use wait_event() to wait for the rcuscale test to complete. However,
each updater thread in such a test waits for at least 100 grace periods.
If each grace period takes more than 1.2 seconds, which is long, but
not insanely so, this can trigger the hung-task timeout.

This commit therefore replaces those wait_event() calls with calls to
wait_event_idle(), which do not trigger the hung-task timeout.

Reported-by: kernel test robot <yujie.liu@intel.com>
Reported-by: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

rcu/rcuscale: Use call_rcu_hurry() for async reader test

rcuscale uses call_rcu() to queue async readers. With recent changes to
save power, the test will have fewer async readers in flight. Use the
call_rcu_hurry() API instead to revert to the old behavior.

[ paulmck: Apply s/call_rcu_flush/call_rcu_hurry/ feedback from Tejun Heo. ]

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Add laziness and kfree tests

This commit adds 2 tests to rcuscale. The first one is a startup test
to check whether we are not too lazy or too hard working. The second
one causes kfree_rcu() itself to use call_rcu() and checks memory
pressure. Testing indicates that the new call_rcu() keeps memory pressure
under control roughly as well as does kfree_rcu().

[ paulmck: Apply checkpatch feedback. ]

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Fix smp_processor_id()-in-preemptible warnings

Systems built with CONFIG_DEBUG_PREEMPT=y can trigger the following
BUG while running the rcuscale performance test:

BUG: using smp_processor_id() in preemptible [00000000] code: rcu_scale_write/69
CPU: 0 PID: 66 Comm: rcu_scale_write Not tainted 5.18.0-rc7-next-20220517-yoctodev-standard+
caller is debug_smp_processor_id+0x17/0x20
Call Trace:
<TASK>
dump_stack_lvl+0x49/0x5e
dump_stack+0x10/0x12
check_preemption_disabled+0xdf/0xf0
debug_smp_processor_id+0x17/0x20
rcu_scale_writer+0x2b5/0x580
kthread+0x177/0x1b0
ret_from_fork+0x22/0x30
</TASK>

Reproduction method:
runqemu kvm slirp nographic qemuparams="-m 4096 -smp 8" bootparams="isolcpus=2,3
nohz_full=2,3 rcu_nocbs=2,3 rcutree.dump_tree=1 rcuscale.shutdown=false
rcuscale.gp_async=true" -d

The problem is that the rcu_scale_writer() kthreads fail to set the
PF_NO_SETAFFINITY flags, which causes is_percpu_thread() to assume
that the kthread's affinity might change at any time, thus the BUG
noted above.

This commit therefore causes rcu_scale_writer() to set PF_NO_SETAFFINITY
in its kthread's ->flags field, thus preventing this BUG.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Allow rcuscale without RCU Tasks Rude/Trace

Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks Rude and RCU Tasks Trace. Unless that kernel builds rcuscale,
whether built-in or as a module, in which case these RCU Tasks flavors are
(unnecessarily) built in. This both increases kernel size and increases
the complexity of certain tracing operations. This commit therefore
decouples the presence of rcuscale from the presence of RCU Tasks Rude
and RCU Tasks Trace.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Allow rcuscale without RCU Tasks

Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks. Unless that kernel builds rcuscale, whether built-in or as
a module, in which case RCU Tasks is (unnecessarily) built. This both
increases kernel size and increases the complexity of certain tracing
operations. This commit therefore decouples the presence of rcuscale
from the presence of RCU Tasks.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Always log error message

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>

rcuscale: Warn on individual rcu_scale_init() error conditions

When running rcuscale as a module, any rcu_scale_init() issues will be
reflected in the error code from modprobe or insmod, as the case may be.
However, these error codes are not available when running rcuscale
built-in, for example, when using the kvm.sh script. This commit
therefore adds WARN_ON_ONCE() to allow distinguishing rcu_scale_init()
errors when running rcuscale built-in.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Console output claims too few grace periods

The rcuscale console output claims N grace periods, numbered from zero
to N, which means that there were really N+1 grace periods. The root
cause of this bug is that rcu_scale_writer() stores the number of the
last grace period (numbered from zero) into writer_n_durations[me]
instead of the number of grace periods. This commit therefore assigns
the actual number of grace periods to writer_n_durations[me], and also
makes the corresponding adjustment to the loop outputting per-grace-period
measurements.

Sample of old console output:
rcu-scale: writer 0 gps: 133
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410

Sample of new console output:
rcu-scale: writer 0 gps: 134
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410

Signed-off-by: Jiangong.Han <jiangong.han@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Add kfree_rcu() single-argument scale test

The single-argument variant of kfree_rcu() is currently not
tested by any member of the rcutoture test suite. This
commit therefore adds rcuscale code to test it. This
testing is controlled by two new boolean module parameters,
kfree_rcu_test_single and kfree_rcu_test_double. If one
is set and the other not, only the corresponding variant
is tested, otherwise both are tested, with the variant to
be tested determined randomly on each invocation.

Both of these module parameters are initialized to false,
so setting either to true will test only that variant.

Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Prevent hangs for invalid arguments

If an rcuscale torture-test run is given a bad kvm.sh argument, the
test will complain to the console, which is good. What is bad is that
from the user's perspective, it will just hang for the time specified
by the --duration argument. This commit therefore forces an immediate
kernel shutdown if a rcu_scale_init()-time error occurs, thus avoiding
the appearance of a hang. It also forces a console splat in this case
to clearly indicate the presence of an error.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuscale: Add RCU Tasks Trace

This commit adds the ability to test performance and scalability of RCU
Tasks Trace updaters.

Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcuperf: Change rcuperf to rcuscale

This commit further avoids conflation of rcuperf with the kernel's perf
feature by renaming kernel/rcu/rcuperf.c to kernel/rcu/rcuscale.c, and
also by similarly renaming the functions and variables inside this file.
This has the side effect of changing the names of the kernel boot
parameters, so kernel-parameters.txt and ver_functions.sh are also
updated. The rcutorture --torture type was also updated from rcuperf
to rcuscale.

[ paulmck: Fix bugs located by Stephen Rothwell. ]
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>