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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright 2023 Red Hat
*/
#ifndef UDS_THREADS_H
#define UDS_THREADS_H
#include <linux/atomic.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <linux/mutex.h>
#include <linux/semaphore.h>
#include <linux/wait.h>
#include "errors.h"
#include "time-utils.h"
/* Thread and synchronization utilities for UDS */
struct cond_var {
wait_queue_head_t wait_queue;
};
struct thread;
struct barrier {
/* Mutex for this barrier object */
struct semaphore mutex;
/* Semaphore for threads waiting at the barrier */
struct semaphore wait;
/* Number of threads which have arrived */
int arrived;
/* Total number of threads using this barrier */
int thread_count;
};
int __must_check uds_create_thread(void (*thread_function)(void *), void *thread_data,
const char *name, struct thread **new_thread);
void uds_perform_once(atomic_t *once_state, void (*function) (void));
int uds_join_threads(struct thread *thread);
int __must_check uds_initialize_barrier(struct barrier *barrier,
unsigned int thread_count);
int uds_destroy_barrier(struct barrier *barrier);
int uds_enter_barrier(struct barrier *barrier);
int __must_check uds_init_cond(struct cond_var *cond);
int uds_signal_cond(struct cond_var *cond);
int uds_broadcast_cond(struct cond_var *cond);
int uds_wait_cond(struct cond_var *cond, struct mutex *mutex);
int uds_destroy_cond(struct cond_var *cond);
static inline int __must_check uds_init_mutex(struct mutex *mutex)
{
mutex_init(mutex);
return UDS_SUCCESS;
}
static inline int uds_destroy_mutex(struct mutex *mutex)
{
return UDS_SUCCESS;
}
static inline void uds_lock_mutex(struct mutex *mutex)
{
mutex_lock(mutex);
}
static inline void uds_unlock_mutex(struct mutex *mutex)
{
mutex_unlock(mutex);
}
static inline int __must_check uds_initialize_semaphore(struct semaphore *semaphore,
unsigned int value)
{
sema_init(semaphore, value);
return UDS_SUCCESS;
}
static inline int uds_destroy_semaphore(struct semaphore *semaphore)
{
return UDS_SUCCESS;
}
static inline void uds_acquire_semaphore(struct semaphore *semaphore)
{
/*
* Do not use down(semaphore). Instead use down_interruptible so that
* we do not get 120 second stall messages in kern.log.
*/
while (down_interruptible(semaphore) != 0) {
/*
* If we're called from a user-mode process (e.g., "dmsetup
* remove") while waiting for an operation that may take a
* while (e.g., UDS index save), and a signal is sent (SIGINT,
* SIGUSR2), then down_interruptible will not block. If that
* happens, sleep briefly to avoid keeping the CPU locked up in
* this loop. We could just call cond_resched, but then we'd
* still keep consuming CPU time slices and swamp other threads
* trying to do computational work. [VDO-4980]
*/
fsleep(1000);
}
}
static inline void uds_release_semaphore(struct semaphore *semaphore)
{
up(semaphore);
}
#endif /* UDS_THREADS_H */
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