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/*-
* Copyright (c) 2017 Mellanox Technologies, Ltd.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <sys/queue.h>
#include <linux/sched.h>
#include <linux/ww_mutex.h>
struct ww_mutex_thread {
TAILQ_ENTRY(ww_mutex_thread) entry;
struct thread *thread;
struct ww_mutex *lock;
};
static TAILQ_HEAD(, ww_mutex_thread) ww_mutex_head;
static struct mtx ww_mutex_global;
static void
linux_ww_init(void *arg)
{
TAILQ_INIT(&ww_mutex_head);
mtx_init(&ww_mutex_global, "lkpi-ww-mtx", NULL, MTX_DEF);
}
SYSINIT(ww_init, SI_SUB_LOCK, SI_ORDER_SECOND, linux_ww_init, NULL);
static void
linux_ww_uninit(void *arg)
{
mtx_destroy(&ww_mutex_global);
}
SYSUNINIT(ww_uninit, SI_SUB_LOCK, SI_ORDER_SECOND, linux_ww_uninit, NULL);
static inline void
linux_ww_lock(void)
{
mtx_lock(&ww_mutex_global);
}
static inline void
linux_ww_unlock(void)
{
mtx_unlock(&ww_mutex_global);
}
/* lock a mutex with deadlock avoidance */
int
linux_ww_mutex_lock_sub(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx, int catch_signal)
{
struct task_struct *task;
struct ww_mutex_thread entry;
struct ww_mutex_thread *other;
int retval = 0;
task = current;
linux_ww_lock();
if (unlikely(sx_try_xlock(&lock->base.sx) == 0)) {
entry.thread = curthread;
entry.lock = lock;
TAILQ_INSERT_TAIL(&ww_mutex_head, &entry, entry);
do {
struct thread *owner = (struct thread *)
SX_OWNER(lock->base.sx.sx_lock);
/* scan for deadlock */
TAILQ_FOREACH(other, &ww_mutex_head, entry) {
/* skip own thread */
if (other == &entry)
continue;
/*
* If another thread is owning our
* lock and is at the same time trying
* to acquire a lock this thread owns,
* that means deadlock.
*/
if (other->thread == owner &&
(struct thread *)SX_OWNER(
other->lock->base.sx.sx_lock) == curthread) {
retval = -EDEADLK;
goto done;
}
}
if (catch_signal) {
retval = -cv_wait_sig(&lock->condvar, &ww_mutex_global);
if (retval != 0) {
linux_schedule_save_interrupt_value(task, retval);
retval = -EINTR;
goto done;
}
} else {
cv_wait(&lock->condvar, &ww_mutex_global);
}
} while (sx_try_xlock(&lock->base.sx) == 0);
done:
TAILQ_REMOVE(&ww_mutex_head, &entry, entry);
/* if the lock is free, wakeup next lock waiter, if any */
if ((struct thread *)SX_OWNER(lock->base.sx.sx_lock) == NULL)
cv_signal(&lock->condvar);
}
if (retval == 0)
lock->ctx = ctx;
linux_ww_unlock();
return (retval);
}
void
linux_ww_mutex_unlock_sub(struct ww_mutex *lock)
{
/* protect ww_mutex ownership change */
linux_ww_lock();
lock->ctx = NULL;
sx_xunlock(&lock->base.sx);
/* wakeup a lock waiter, if any */
cv_signal(&lock->condvar);
linux_ww_unlock();
}
int
linux_mutex_lock_interruptible(mutex_t *m)
{
int error;
error = -sx_xlock_sig(&m->sx);
if (error != 0) {
linux_schedule_save_interrupt_value(current, error);
error = -EINTR;
}
return (error);
}
int
linux_down_write_killable(struct rw_semaphore *rw)
{
int error;
error = -sx_xlock_sig(&rw->sx);
if (error != 0) {
linux_schedule_save_interrupt_value(current, error);
error = -EINTR;
}
return (error);
}
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