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Thu, 17 Apr 2025 09:12:19 -0700 (PDT) Received: from pc638.lan ([2001:9b1:d5a0:a500:2d8:61ff:fec9:d743]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54d6df60cf6sm2882e87.66.2025.04.17.09.12.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Apr 2025 09:12:18 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: Andrew Morton Cc: linux-mm@kvack.org, LKML , Baoquan He , Christoph Hellwig , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH 1/4] lib/test_vmalloc.c: Replace RWSEM to SRCU for setup Date: Thu, 17 Apr 2025 18:12:13 +0200 Message-Id: <20250417161216.88318-1-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 X-Rspamd-Queue-Id: 2199F100005 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 9pyphjr6yaqnufuqdjcx781xi3z1ks8f X-HE-Tag: 1744906340-560917 X-HE-Meta: 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 CleViRwD zzRJzJVAHHJwmq3jQNdfhOho7xiu4/oYlyC+EM1Ql+5ewBi/h+HnymVan13Fni4Qef2U+1snKRUCQZleSJkhv9WW4lgmxl7lFcjQ58wJMHRhLyH6Iybqh/w/W2iAciw2MX83L1zXIw8szX3pTrFjkJQdd+9CRoJGCrS4ZkHM6o+9cOzEIJiYB/wI4QTwi7lJmz5eBIuOXYcCQcj3mrckHEybddbTgT1OxwPeto/O+7YWQjQHPGiOqe0dRhm/gAj9oC/YCoesQgqyPO82S0S6N992lu2SHjlYQlJwojKESYSui0rqaMmEQ4SHygTStlqVAU73fLZWPgxBorWJhkrg6STkcIymGaWbuB34T3BVrlBhwmbE7aKFqjJSDKh8lM6ifHaIQC5mZUhlKl2RHtpdcQmQitLUx/9Yb0pTRD46Ned/PkQE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Signed-off-by: Uladzislau Rezki (Sony) --- lib/test_vmalloc.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c index f585949ff696e..4ab23e5e772d0 100644 --- a/lib/test_vmalloc.c +++ b/lib/test_vmalloc.c @@ -13,9 +13,9 @@ #include #include #include -#include #include #include +#include #include #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