/* $Id: thread-r0drv-linux.c 109136 2016-07-26 15:20:12Z bird $ */
/** @file
 * IPRT - Threads, Ring-0 Driver, Linux.
 */

/*
 * Copyright (C) 2006-2016 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
 * VirtualBox OSE distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 */

/*********************************************************************************************************************************
*   Header Files                                                                                                                 *
*********************************************************************************************************************************/
#include "the-linux-kernel.h"
#include "internal/iprt.h"
#include <iprt/thread.h>

#include <iprt/asm.h>
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 5, 28) || defined(CONFIG_X86_SMAP)
# include <iprt/asm-amd64-x86.h>
#endif
#include <iprt/assert.h>
#include <iprt/err.h>
#include <iprt/mp.h>

/*********************************************************************************************************************************
*   Global Variables                                                                                                             *
*********************************************************************************************************************************/
#ifndef CONFIG_PREEMPT
/** Per-cpu preemption counters. */
static int32_t volatile g_acPreemptDisabled[NR_CPUS];
#endif

RTDECL(RTNATIVETHREAD) RTThreadNativeSelf(void)
{
	return (RTNATIVETHREAD) current;
}

RT_EXPORT_SYMBOL(RTThreadNativeSelf);

static int rtR0ThreadLnxSleepCommon(RTMSINTERVAL cMillies)
{
	IPRT_LINUX_SAVE_EFL_AC();
	long cJiffies = msecs_to_jiffies(cMillies);
	set_current_state(TASK_INTERRUPTIBLE);
	cJiffies = schedule_timeout(cJiffies);
	IPRT_LINUX_RESTORE_EFL_AC();
	if (!cJiffies)
		return VINF_SUCCESS;
	return VERR_INTERRUPTED;
}

RTDECL(int)RTThreadSleep(RTMSINTERVAL cMillies)
{
	return rtR0ThreadLnxSleepCommon(cMillies);
}

RT_EXPORT_SYMBOL(RTThreadSleep);

RTDECL(int)RTThreadSleepNoLog(RTMSINTERVAL cMillies)
{
	return rtR0ThreadLnxSleepCommon(cMillies);
}

RT_EXPORT_SYMBOL(RTThreadSleepNoLog);

RTDECL(bool) RTThreadYield(void)
{
	IPRT_LINUX_SAVE_EFL_AC();
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 4, 20)
	yield();
#else
    /** @todo r=ramshankar: Can we use cond_resched() instead?  */
	set_current_state(TASK_RUNNING);
	sys_sched_yield();
	schedule();
#endif
	IPRT_LINUX_RESTORE_EFL_AC();
	return true;
}

RT_EXPORT_SYMBOL(RTThreadYield);

RTDECL(bool) RTThreadPreemptIsEnabled(RTTHREAD hThread)
{
#ifdef CONFIG_PREEMPT
	Assert(hThread == NIL_RTTHREAD);
	RT_NOREF_PV(hThread);
# ifdef preemptible
	return preemptible();
# else
	return preempt_count() == 0 && !in_atomic() && !irqs_disabled();
# endif
#else
	int32_t c;

	Assert(hThread == NIL_RTTHREAD);
	c = g_acPreemptDisabled[smp_processor_id()];
	AssertMsg(c >= 0 && c < 32, ("%d\n", c));
	if (c != 0)
		return false;
# if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 32)
	if (in_atomic())
		return false;
# endif
# if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 28)
	if (irqs_disabled())
		return false;
# else
	if (!ASMIntAreEnabled())
		return false;
# endif
	return true;
#endif
}

RT_EXPORT_SYMBOL(RTThreadPreemptIsEnabled);

RTDECL(bool) RTThreadPreemptIsPending(RTTHREAD hThread)
{
	Assert(hThread == NIL_RTTHREAD);
	RT_NOREF_PV(hThread);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 4)
	return !!test_tsk_thread_flag(current, TIF_NEED_RESCHED);

#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2, 4, 20)
	return !!need_resched();

#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2, 1, 110)
	return current->need_resched != 0;

#else
	return need_resched != 0;
#endif
}

RT_EXPORT_SYMBOL(RTThreadPreemptIsPending);

RTDECL(bool) RTThreadPreemptIsPendingTrusty(void)
{
	/* yes, RTThreadPreemptIsPending is reliable. */
	return true;
}

RT_EXPORT_SYMBOL(RTThreadPreemptIsPendingTrusty);

RTDECL(bool) RTThreadPreemptIsPossible(void)
{
    /** @todo r=ramshankar: What about CONFIG_PREEMPT_VOLUNTARY? That can preempt
     *        too but does so in voluntarily in explicit preemption points. */
#ifdef CONFIG_PREEMPT
	return true;		/* yes, kernel preemption is possible. */
#else
	return false;		/* no kernel preemption */
#endif
}

RT_EXPORT_SYMBOL(RTThreadPreemptIsPossible);

RTDECL(void)RTThreadPreemptDisable(PRTTHREADPREEMPTSTATE pState)
{
#ifdef CONFIG_PREEMPT
	AssertPtr(pState);
	Assert(pState->u32Reserved == 0);
	pState->u32Reserved = 42;
	/* This ASSUMES that CONFIG_PREEMPT_COUNT is always defined with CONFIG_PREEMPT. */
	preempt_disable();
	RT_ASSERT_PREEMPT_CPUID_DISABLE(pState);

#else /* !CONFIG_PREEMPT */
	int32_t c;
	AssertPtr(pState);
	Assert(pState->u32Reserved == 0);

	/* Do our own accounting. */
	c = ASMAtomicIncS32(&g_acPreemptDisabled[smp_processor_id()]);
	AssertMsg(c > 0 && c < 32, ("%d\n", c));
	pState->u32Reserved = c;
	RT_ASSERT_PREEMPT_CPUID_DISABLE(pState);
#endif
}

RT_EXPORT_SYMBOL(RTThreadPreemptDisable);

RTDECL(void) RTThreadPreemptRestore(PRTTHREADPREEMPTSTATE pState)
{
#ifdef CONFIG_PREEMPT
	IPRT_LINUX_SAVE_EFL_AC();	/* paranoia */
	AssertPtr(pState);
	Assert(pState->u32Reserved == 42);
	RT_ASSERT_PREEMPT_CPUID_RESTORE(pState);
	preempt_enable();
	IPRT_LINUX_RESTORE_EFL_ONLY_AC();	/* paranoia */

#else
	int32_t volatile *pc;
	AssertPtr(pState);
	AssertMsg(pState->u32Reserved > 0
		  && pState->u32Reserved < 32, ("%d\n", pState->u32Reserved));
	RT_ASSERT_PREEMPT_CPUID_RESTORE(pState);

	/* Do our own accounting. */
	pc = &g_acPreemptDisabled[smp_processor_id()];
	AssertMsg(pState->u32Reserved == (uint32_t) * pc,
		  ("u32Reserved=%d *pc=%d \n", pState->u32Reserved, *pc));
	ASMAtomicUoWriteS32(pc, pState->u32Reserved - 1);
#endif
	pState->u32Reserved = 0;
}

RT_EXPORT_SYMBOL(RTThreadPreemptRestore);

RTDECL(bool) RTThreadIsInInterrupt(RTTHREAD hThread)
{
	Assert(hThread == NIL_RTTHREAD);
	NOREF(hThread);

	return in_interrupt() != 0;
}

RT_EXPORT_SYMBOL(RTThreadIsInInterrupt);
