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ede0bdffb6
When HAVE_MUTEX_OWNER is defined and we are directly accessing mutex->owner treat is as volative with the ACCESS_ONCE() helper. Without this you may get a stale cached value when accessing it from different cpus. This can result in incorrect behavior from mutex_owned() and mutex_owner(). This is not a problem for the !HAVE_MUTEX_OWNER case because in this case all the accesses are covered by a spin lock which similarly gaurentees we will not be accessing stale data. Secondly, check CONFIG_SMP before allowing access to mutex->owner. I see that for non-SMP setups the kernel does not track the owner so we cannot rely on it. Thirdly, check CONFIG_MUTEX_DEBUG when this is defined and the HAVE_MUTEX_OWNER is defined surprisingly the mutex->owner will not be cleared on mutex_exit(). When this is the case the SPL needs to make sure to do it to ensure MUTEX_HELD() behaves as expected or you will certainly assert in mutex_destroy(). Finally, improve the mutex regression tests. For mutex_owned() we now minimally check that it behaves correctly when checked from the owner thread or the non-owner thread. This subtle behaviour has bit me before and I'd like to catch it early next time if it reappears. As for mutex_owned() regression test additonally verify that mutex->owner is always cleared on mutex_exit().
438 lines
15 KiB
C
438 lines
15 KiB
C
/*****************************************************************************\
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://github.com/behlendorf/spl/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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*****************************************************************************
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* Solaris Porting LAyer Tests (SPLAT) Mutex Tests.
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\*****************************************************************************/
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#include "splat-internal.h"
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#define SPLAT_MUTEX_NAME "mutex"
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#define SPLAT_MUTEX_DESC "Kernel Mutex Tests"
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#define SPLAT_MUTEX_TEST1_ID 0x0401
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#define SPLAT_MUTEX_TEST1_NAME "tryenter"
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#define SPLAT_MUTEX_TEST1_DESC "Validate mutex_tryenter() correctness"
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#define SPLAT_MUTEX_TEST2_ID 0x0402
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#define SPLAT_MUTEX_TEST2_NAME "race"
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#define SPLAT_MUTEX_TEST2_DESC "Many threads entering/exiting the mutex"
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#define SPLAT_MUTEX_TEST3_ID 0x0403
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#define SPLAT_MUTEX_TEST3_NAME "owned"
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#define SPLAT_MUTEX_TEST3_DESC "Validate mutex_owned() correctness"
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#define SPLAT_MUTEX_TEST4_ID 0x0404
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#define SPLAT_MUTEX_TEST4_NAME "owner"
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#define SPLAT_MUTEX_TEST4_DESC "Validate mutex_owner() correctness"
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#define SPLAT_MUTEX_TEST_MAGIC 0x115599DDUL
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#define SPLAT_MUTEX_TEST_NAME "mutex_test"
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#define SPLAT_MUTEX_TEST_TASKQ "mutex_taskq"
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#define SPLAT_MUTEX_TEST_COUNT 128
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typedef struct mutex_priv {
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unsigned long mp_magic;
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struct file *mp_file;
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kmutex_t mp_mtx;
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int mp_rc;
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int mp_rc2;
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} mutex_priv_t;
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static void
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splat_mutex_test1_func(void *arg)
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{
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mutex_priv_t *mp = (mutex_priv_t *)arg;
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ASSERT(mp->mp_magic == SPLAT_MUTEX_TEST_MAGIC);
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if (mutex_tryenter(&mp->mp_mtx)) {
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mp->mp_rc = 0;
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mutex_exit(&mp->mp_mtx);
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} else {
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mp->mp_rc = -EBUSY;
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}
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}
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static int
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splat_mutex_test1(struct file *file, void *arg)
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{
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mutex_priv_t *mp;
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taskq_t *tq;
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int id, rc = 0;
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mp = (mutex_priv_t *)kmalloc(sizeof(*mp), GFP_KERNEL);
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if (mp == NULL)
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return -ENOMEM;
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tq = taskq_create(SPLAT_MUTEX_TEST_TASKQ, 1, maxclsyspri,
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50, INT_MAX, TASKQ_PREPOPULATE);
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if (tq == NULL) {
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rc = -ENOMEM;
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goto out2;
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}
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mp->mp_magic = SPLAT_MUTEX_TEST_MAGIC;
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mp->mp_file = file;
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mutex_init(&mp->mp_mtx, SPLAT_MUTEX_TEST_NAME, MUTEX_DEFAULT, NULL);
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mutex_enter(&mp->mp_mtx);
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/*
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* Schedule a task function which will try and acquire the mutex via
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* mutex_tryenter() while it's held. This should fail and the task
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* function will indicate this status in the passed private data.
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*/
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mp->mp_rc = -EINVAL;
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id = taskq_dispatch(tq, splat_mutex_test1_func, mp, TQ_SLEEP);
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if (id == 0) {
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mutex_exit(&mp->mp_mtx);
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splat_vprint(file, SPLAT_MUTEX_TEST1_NAME, "%s",
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"taskq_dispatch() failed\n");
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rc = -EINVAL;
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goto out;
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}
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taskq_wait_id(tq, id);
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mutex_exit(&mp->mp_mtx);
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/* Task function successfully acquired mutex, very bad! */
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if (mp->mp_rc != -EBUSY) {
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splat_vprint(file, SPLAT_MUTEX_TEST1_NAME,
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"mutex_trylock() incorrectly succeeded when "
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"the mutex was held, %d/%d\n", id, mp->mp_rc);
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rc = -EINVAL;
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goto out;
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} else {
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splat_vprint(file, SPLAT_MUTEX_TEST1_NAME, "%s",
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"mutex_trylock() correctly failed when "
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"the mutex was held\n");
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}
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/*
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* Schedule a task function which will try and acquire the mutex via
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* mutex_tryenter() while it is not held. This should succeed and
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* can be verified by checking the private data.
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*/
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mp->mp_rc = -EINVAL;
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id = taskq_dispatch(tq, splat_mutex_test1_func, mp, TQ_SLEEP);
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if (id == 0) {
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splat_vprint(file, SPLAT_MUTEX_TEST1_NAME, "%s",
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"taskq_dispatch() failed\n");
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rc = -EINVAL;
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goto out;
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}
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taskq_wait_id(tq, id);
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/* Task function failed to acquire mutex, very bad! */
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if (mp->mp_rc != 0) {
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splat_vprint(file, SPLAT_MUTEX_TEST1_NAME,
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"mutex_trylock() incorrectly failed when "
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"the mutex was not held, %d/%d\n", id, mp->mp_rc);
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rc = -EINVAL;
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} else {
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splat_vprint(file, SPLAT_MUTEX_TEST1_NAME, "%s",
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"mutex_trylock() correctly succeeded "
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"when the mutex was not held\n");
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}
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out:
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taskq_destroy(tq);
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mutex_destroy(&(mp->mp_mtx));
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out2:
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kfree(mp);
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return rc;
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}
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static void
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splat_mutex_test2_func(void *arg)
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{
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mutex_priv_t *mp = (mutex_priv_t *)arg;
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int rc;
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ASSERT(mp->mp_magic == SPLAT_MUTEX_TEST_MAGIC);
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/* Read the value before sleeping and write it after we wake up to
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* maximize the chance of a race if mutexs are not working properly */
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mutex_enter(&mp->mp_mtx);
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rc = mp->mp_rc;
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set_current_state(TASK_INTERRUPTIBLE);
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schedule_timeout(HZ / 100); /* 1/100 of a second */
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VERIFY(mp->mp_rc == rc);
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mp->mp_rc = rc + 1;
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mutex_exit(&mp->mp_mtx);
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}
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static int
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splat_mutex_test2(struct file *file, void *arg)
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{
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mutex_priv_t *mp;
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taskq_t *tq;
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int i, rc = 0;
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mp = (mutex_priv_t *)kmalloc(sizeof(*mp), GFP_KERNEL);
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if (mp == NULL)
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return -ENOMEM;
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/* Create several threads allowing tasks to race with each other */
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tq = taskq_create(SPLAT_MUTEX_TEST_TASKQ, num_online_cpus(),
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maxclsyspri, 50, INT_MAX, TASKQ_PREPOPULATE);
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if (tq == NULL) {
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rc = -ENOMEM;
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goto out;
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}
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mp->mp_magic = SPLAT_MUTEX_TEST_MAGIC;
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mp->mp_file = file;
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mutex_init(&(mp->mp_mtx), SPLAT_MUTEX_TEST_NAME, MUTEX_DEFAULT, NULL);
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mp->mp_rc = 0;
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/*
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* Schedule N work items to the work queue each of which enters the
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* mutex, sleeps briefly, then exits the mutex. On a multiprocessor
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* box these work items will be handled by all available CPUs. The
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* task function checks to ensure the tracked shared variable is
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* always only incremented by one. Additionally, the mutex itself
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* is instrumented such that if any two processors are in the
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* critical region at the same time the system will panic. If the
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* mutex is implemented right this will never happy, that's a pass.
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*/
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for (i = 0; i < SPLAT_MUTEX_TEST_COUNT; i++) {
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if (!taskq_dispatch(tq, splat_mutex_test2_func, mp, TQ_SLEEP)) {
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splat_vprint(file, SPLAT_MUTEX_TEST2_NAME,
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"Failed to queue task %d\n", i);
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rc = -EINVAL;
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}
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}
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taskq_wait(tq);
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if (mp->mp_rc == SPLAT_MUTEX_TEST_COUNT) {
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splat_vprint(file, SPLAT_MUTEX_TEST2_NAME, "%d racing threads "
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"correctly entered/exited the mutex %d times\n",
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num_online_cpus(), mp->mp_rc);
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} else {
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splat_vprint(file, SPLAT_MUTEX_TEST2_NAME, "%d racing threads "
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"only processed %d/%d mutex work items\n",
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num_online_cpus(),mp->mp_rc,SPLAT_MUTEX_TEST_COUNT);
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rc = -EINVAL;
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}
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taskq_destroy(tq);
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mutex_destroy(&(mp->mp_mtx));
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out:
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kfree(mp);
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return rc;
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}
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static void
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splat_mutex_owned(void *priv)
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{
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mutex_priv_t *mp = (mutex_priv_t *)priv;
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ASSERT(mp->mp_magic == SPLAT_MUTEX_TEST_MAGIC);
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mp->mp_rc = mutex_owned(&mp->mp_mtx);
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mp->mp_rc2 = MUTEX_HELD(&mp->mp_mtx);
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}
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static int
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splat_mutex_test3(struct file *file, void *arg)
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{
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mutex_priv_t mp;
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taskq_t *tq;
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int rc = 0;
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mp.mp_magic = SPLAT_MUTEX_TEST_MAGIC;
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mp.mp_file = file;
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mutex_init(&mp.mp_mtx, SPLAT_MUTEX_TEST_NAME, MUTEX_DEFAULT, NULL);
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if ((tq = taskq_create(SPLAT_MUTEX_TEST_NAME, 1, maxclsyspri,
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50, INT_MAX, TASKQ_PREPOPULATE)) == NULL) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Taskq '%s' "
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"create failed\n", SPLAT_MUTEX_TEST3_NAME);
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return -EINVAL;
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}
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mutex_enter(&mp.mp_mtx);
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/* Mutex should be owned by current */
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if (!mutex_owned(&mp.mp_mtx)) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Unowned mutex "
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"should be owned by pid %d\n", current->pid);
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rc = -EINVAL;
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goto out_exit;
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}
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if (taskq_dispatch(tq, splat_mutex_owned, &mp, TQ_SLEEP) == 0) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Failed to "
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"dispatch function '%s' to taskq\n",
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sym2str(splat_mutex_owned));
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rc = -EINVAL;
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goto out_exit;
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}
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taskq_wait(tq);
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/* Mutex should not be owned which checked from a different thread */
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if (mp.mp_rc || mp.mp_rc2) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Mutex owned by "
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"pid %d not by taskq\n", current->pid);
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rc = -EINVAL;
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goto out_exit;
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}
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mutex_exit(&mp.mp_mtx);
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/* Mutex should not be owned by current */
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if (mutex_owned(&mp.mp_mtx)) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Mutex owned by "
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"pid %d it should be unowned\b", current->pid);
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rc = -EINVAL;
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goto out;
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}
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if (taskq_dispatch(tq, splat_mutex_owned, &mp, TQ_SLEEP) == 0) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Failed to "
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"dispatch function '%s' to taskq\n",
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sym2str(splat_mutex_owned));
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rc = -EINVAL;
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goto out;
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}
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taskq_wait(tq);
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/* Mutex should be owned by no one */
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if (mp.mp_rc || mp.mp_rc2) {
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "Mutex owned by "
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"no one, %d/%d disagrees\n", mp.mp_rc, mp.mp_rc2);
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rc = -EINVAL;
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goto out;
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}
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "%s",
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"Correct mutex_owned() behavior\n");
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goto out;
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out_exit:
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mutex_exit(&mp.mp_mtx);
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out:
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mutex_destroy(&mp.mp_mtx);
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taskq_destroy(tq);
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return rc;
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}
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static int
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splat_mutex_test4(struct file *file, void *arg)
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{
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kmutex_t mtx;
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kthread_t *owner;
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int rc = 0;
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mutex_init(&mtx, SPLAT_MUTEX_TEST_NAME, MUTEX_DEFAULT, NULL);
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/*
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* Verify mutex owner is cleared after being dropped. Depending
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* on how you build your kernel this behavior changes, ensure the
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* SPL mutex implementation is properly detecting this.
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*/
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mutex_enter(&mtx);
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msleep(100);
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mutex_exit(&mtx);
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if (MUTEX_HELD(&mtx)) {
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splat_vprint(file, SPLAT_MUTEX_TEST4_NAME, "Mutex should "
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"not be held, bit is by %p\n", mutex_owner(&mtx));
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rc = -EINVAL;
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goto out;
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}
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mutex_enter(&mtx);
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/* Mutex should be owned by current */
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owner = mutex_owner(&mtx);
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if (current != owner) {
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splat_vprint(file, SPLAT_MUTEX_TEST4_NAME, "Mutex should "
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"be owned by pid %d but is owned by pid %d\n",
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current->pid, owner ? owner->pid : -1);
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rc = -EINVAL;
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goto out;
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}
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mutex_exit(&mtx);
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/* Mutex should not be owned by any task */
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owner = mutex_owner(&mtx);
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if (owner) {
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splat_vprint(file, SPLAT_MUTEX_TEST4_NAME, "Mutex should not "
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"be owned but is owned by pid %d\n", owner->pid);
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rc = -EINVAL;
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goto out;
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}
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splat_vprint(file, SPLAT_MUTEX_TEST3_NAME, "%s",
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"Correct mutex_owner() behavior\n");
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out:
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mutex_destroy(&mtx);
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return rc;
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}
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splat_subsystem_t *
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splat_mutex_init(void)
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{
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splat_subsystem_t *sub;
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sub = kmalloc(sizeof(*sub), GFP_KERNEL);
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if (sub == NULL)
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return NULL;
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memset(sub, 0, sizeof(*sub));
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strncpy(sub->desc.name, SPLAT_MUTEX_NAME, SPLAT_NAME_SIZE);
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strncpy(sub->desc.desc, SPLAT_MUTEX_DESC, SPLAT_DESC_SIZE);
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INIT_LIST_HEAD(&sub->subsystem_list);
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INIT_LIST_HEAD(&sub->test_list);
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spin_lock_init(&sub->test_lock);
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sub->desc.id = SPLAT_SUBSYSTEM_MUTEX;
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SPLAT_TEST_INIT(sub, SPLAT_MUTEX_TEST1_NAME, SPLAT_MUTEX_TEST1_DESC,
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SPLAT_MUTEX_TEST1_ID, splat_mutex_test1);
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SPLAT_TEST_INIT(sub, SPLAT_MUTEX_TEST2_NAME, SPLAT_MUTEX_TEST2_DESC,
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SPLAT_MUTEX_TEST2_ID, splat_mutex_test2);
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SPLAT_TEST_INIT(sub, SPLAT_MUTEX_TEST3_NAME, SPLAT_MUTEX_TEST3_DESC,
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SPLAT_MUTEX_TEST3_ID, splat_mutex_test3);
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SPLAT_TEST_INIT(sub, SPLAT_MUTEX_TEST4_NAME, SPLAT_MUTEX_TEST4_DESC,
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SPLAT_MUTEX_TEST4_ID, splat_mutex_test4);
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return sub;
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}
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void
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splat_mutex_fini(splat_subsystem_t *sub)
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{
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ASSERT(sub);
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SPLAT_TEST_FINI(sub, SPLAT_MUTEX_TEST4_ID);
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SPLAT_TEST_FINI(sub, SPLAT_MUTEX_TEST3_ID);
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SPLAT_TEST_FINI(sub, SPLAT_MUTEX_TEST2_ID);
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SPLAT_TEST_FINI(sub, SPLAT_MUTEX_TEST1_ID);
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kfree(sub);
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}
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int
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splat_mutex_id(void) {
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return SPLAT_SUBSYSTEM_MUTEX;
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}
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