/*
* Copyright (c) 2020 Red Hat, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* $Id: //eng/vdo-releases/aluminum/src/c++/vdo/kernel/workQueueHandle.h#1 $
*/
#ifndef WORK_QUEUE_HANDLE_H
#define WORK_QUEUE_HANDLE_H
#include <linux/version.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)
#include <linux/sched/task_stack.h>
#else
#include <linux/sched.h>
#endif
#include "workQueueInternals.h"
/*
* Layout of a special structure stored at a consistent place on the
* stack in work queue threads.
*/
typedef struct workQueueStackHandle {
unsigned long nonce;
SimpleWorkQueue *queue;
} WorkQueueStackHandle;
typedef struct workQueueStackHandleGlobals {
/*
* Location in the stack, relative to the task structure which is
* contained in the same memory allocation.
*/
long offset;
/*
* A lock is used to guard against multiple updaters, but once an
* update is done, the offset variable will be read-only.
*/
spinlock_t offsetLock;
/*
* A nonce chosen differently each time the module is loaded, used
* as a marker so we can check that the current thread really is a
* work queue thread. Set at module initialization time, before any
* work queues are created.
*/
unsigned long nonce;
} WorkQueueStackHandleGlobals;
extern WorkQueueStackHandleGlobals workQueueStackHandleGlobals;
/**
* Initialize a stack handle associated with a work queue.
*
* @param [out] handle The handle to be initialized
* @param [in] queue The work queue pointer
**/
void initializeWorkQueueStackHandle(WorkQueueStackHandle *handle,
SimpleWorkQueue *queue);
/**
* Return the work queue pointer recorded at initialization time in
* the work-queue stack handle initialized on the stack of the current
* thread, if any.
*
* @return the work queue pointer, or NULL
**/
static inline SimpleWorkQueue *getCurrentThreadWorkQueue(void)
{
WorkQueueStackHandle *handle
= (WorkQueueStackHandle *)(task_stack_page(current)
+ workQueueStackHandleGlobals.offset);
if (likely(handle->nonce == workQueueStackHandleGlobals.nonce)) {
return handle->queue;
} else {
return NULL;
}
}
/**
* Initialize the global state used by the work-queue stack-handle
* code.
**/
void initWorkQueueStackHandleOnce(void);
#endif // WORK_QUEUE_HANDLE_H