Commit 7a73348e authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Andrew Morton
Browse files

lib/test_vmalloc.c: replace RWSEM to SRCU for setup 

The test has the initialization step during which threads are created.  To
prevent the workers from starting prematurely a write lock was previously
used by the main setup thread, while each worker would block on a read
lock.

Replace this RWSEM based synchronization with a simpler SRCU based
approach.  Which does two basic steps:

- Main thread wraps the setup phase in an SRCU read-side critical
  section.  Pair of srcu_read_lock()/srcu_read_unlock().
- Each worker calls synchronize_srcu() on entry, ensuring it waits for
  the initialization phase to be completed.

This patch eliminates the need for down_read()/up_read() and
down_write()/up_write() pairs thus simplifying the logic and improving
clarity.

[urezki@gmail.com: fix compile error with CONFIG_TINY_RCU]
  Link: https://lkml.kernel.org/r/20250420142029.103169-1-urezki@gmail.com
Link: https://lkml.kernel.org/r/20250417161216.88318-1-urezki@gmail.com


Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: default avatarAdrian Huang <ahuang12@lenovo.com>
Tested-by: default avatarAdrian Huang <ahuang12@lenovo.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Christop Hellwig <hch@infradead.org>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b05f8d7e

lib/test_vmalloc.c

+7 −10
Original line number Diff line number Diff line
@@ -13,9 +13,9 @@ 
#include <linux/moduleparam.h>

#include <linux/completion.h>

#include <linux/delay.h>

#include <linux/rwsem.h>

#include <linux/mm.h>

#include <linux/rcupdate.h>

#include <linux/srcu.h>

#include <linux/slab.h>



#define __param(type, name, init, msg)		\
@@ -58,10 +58,9 @@ __param(int, run_test_mask, INT_MAX, 
);



/*

 * Read write semaphore for synchronization of setup

 * phase that is done in main thread and workers.

 * This is for synchronization of setup phase.

 */

static DECLARE_RWSEM(prepare_for_test_rwsem);

DEFINE_STATIC_SRCU(prepare_for_test_srcu);



/*

 * Completion tracking for worker threads.
@@ -458,7 +457,7 @@ static int test_func(void *private) 
	/*

	 * Block until initialization is done.

	 */

	down_read(&prepare_for_test_rwsem);

	synchronize_srcu(&prepare_for_test_srcu);



	t->start = get_cycles();

	for (i = 0; i < ARRAY_SIZE(test_case_array); i++) {
@@ -487,8 +486,6 @@ static int test_func(void *private) 
		t->data[index].time = delta;

	}

	t->stop = get_cycles();



	up_read(&prepare_for_test_rwsem);

	test_report_one_done();



	/*
@@ -526,7 +523,7 @@ init_test_configuration(void) 


static void do_concurrent_test(void)

{

	int i, ret;

	int i, ret, idx;



	/*

	 * Set some basic configurations plus sanity check.
@@ -538,7 +535,7 @@ static void do_concurrent_test(void) 
	/*

	 * Put on hold all workers.

	 */

	down_write(&prepare_for_test_rwsem);

	idx = srcu_read_lock(&prepare_for_test_srcu);



	for (i = 0; i < nr_threads; i++) {

		struct test_driver *t = &tdriver[i];
@@ -555,7 +552,7 @@ static void do_concurrent_test(void) 
	/*

	 * Now let the workers do their job.

	 */

	up_write(&prepare_for_test_rwsem);

	srcu_read_unlock(&prepare_for_test_srcu, idx);



	/*

	 * Sleep quiet until all workers are done with 1 second