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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: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Adrian Huang <ahuang12@lenovo.com>
Tested-by: Adrian 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Uladzislau Rezki (Sony) 2025-04-17 18:12:13 +02:00 committed by Andrew Morton
parent b05f8d7e07
commit 7a73348e5d
1 changed files with 7 additions and 10 deletions
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17
lib/test_vmalloc.c
View File

@ -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