Set reader_tasks to NULL after kfree() in ref_scale_cleanup() to
improve debugging experience with kernel debugging tools. This
follows the common pattern of NULLing pointers after freeing to
avoid dangling pointer issues during debugging sessions.

Setting pointers to NULL after freeing helps debugging tools like
kdgb,drgn, and other kernel debuggers by providing clear indication
that the memory has been freed and the pointer is no longer valid.

Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Remove unnecessary kfree(main_task) call in ref_scale_cleanup() as
torture_stop_kthread() already handles the memory cleanup for the
task structure internally.

The additional kfree(main_task) call after torture_stop_kthread()
is redundant and confusing since torture_stop_kthread() sets the
pointer to NULL, making this a no-op.

This pattern is consistent with other torture test modules where
torture_stop_kthread() is called without explicit kfree() of the
task pointer, as the torture framework manages the task lifecycle
internally.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Use kcalloc() in main_func() to gain built-in overflow protection, making
memory allocation safer when calculating allocation size compared to
explicit multiplication.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Because SRCU-lite is being replaced by SRCU-fast, this commit removes
support for SRCU-lite from refscale.c.

Both SRCU-lite and SRCU-fast provide faster readers by dropping the
smp_mb() call from their lock and unlock primitives, but incur a pair
of added RCU grace periods during the SRCU grace period.  There is a
trivial mapping from the SRCU-lite API to that of SRCU-fast, so there
should be no transition issues.

[ paulmck: Apply Christoph Hellwig feedback. ]

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>

The nreaders and loops variables are exposed as module parameters, which,
in certain combinations, can lead to multiplication overflow.

Besides, loops parameter is defined as long, while through the code is
used as int, which can cause truncation on 64-bit kernels and possible
zeroes where they shouldn't appear.

Since code uses result of multiplication as int anyway, it only makes sense
to replace loops with int. Multiplication overflow check is also added
due to possible multiplication between two very big numbers.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 653ed64b01dc ("refperf: Add a test to measure performance of read-side synchronization")
Signed-off-by: Artem Sadovnikov <a.sadovnikov@ispras.ru>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>

This commit creates a new srcu-fast option for the refscale.scale_type
module parameter that selects srcu_read_lock_fast() and
srcu_read_unlock_fast().

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

This commit adds a "sched-clock" test for the sched_clock() function.

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

This commit adds a guest_os_delay module parameter that extends warm-up
and cool-down the specified number of seconds before and after the series
of test runs.  This allows the data-collection intervals from any given
rcuscale guest OSes to line up with active periods in the other rcuscale
guest OSes, and also allows the thermal warm-up period required to obtain
consistent results from one test to the next.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>