Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 849 insertions, 0 deletions

diff --git a/src/VBox/Runtime/r3/posix/sched-posix.cpp b/src/VBox/Runtime/r3/posix/sched-posix.cpp
new file mode 100644
index 00000000..b30b9c67
--- /dev/null
+++ b/src/VBox/Runtime/r3/posix/sched-posix.cpp
@@ -0,0 +1,849 @@
+/* $Id: sched-posix.cpp $ */
+/** @file
+ * IPRT - Scheduling, POSIX.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * 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, in version 3 of the
+ * License.
+ *
+ * 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, see <https://www.gnu.org/licenses>.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+ * in the VirtualBox 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.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+ */
+
+/*
+ * !WARNING!
+ *
+ * When talking about lowering and raising priority, we do *NOT* refer to
+ * the common direction priority values takes on unix systems (lower means
+ * higher). So, when we raise the priority of a linux thread the nice
+ * value will decrease, and when we lower the priority the nice value
+ * will increase. Confusing, right?
+ *
+ * !WARNING!
+ */
+
+
+
+/** @def THREAD_LOGGING
+ * Be very careful with enabling this, it may cause deadlocks when combined
+ * with the 'thread' logging prefix.
+ */
+#ifdef DOXYGEN_RUNNING
+#define THREAD_LOGGING
+#endif
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP RTLOGGROUP_THREAD
+#include <errno.h>
+#include <pthread.h>
+#include <sched.h>
+#include <unistd.h>
+#include <sys/resource.h>
+
+#include <iprt/thread.h>
+#include <iprt/process.h>
+#include <iprt/semaphore.h>
+#include <iprt/string.h>
+#include <iprt/assert.h>
+#include <iprt/log.h>
+#include <iprt/err.h>
+#include "internal/sched.h"
+#include "internal/thread.h"
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+
+/** Array scheduler attributes corresponding to each of the thread types. */
+typedef struct PROCPRIORITYTYPE
+{
+    /** For sanity include the array index. */
+    RTTHREADTYPE    enmType;
+    /** The thread priority or nice delta - depends on which priority type. */
+    int             iPriority;
+} PROCPRIORITYTYPE;
+
+
+/**
+ * Configuration of one priority.
+ */
+typedef struct
+{
+    /** The priority. */
+    RTPROCPRIORITY  enmPriority;
+    /** The name of this priority. */
+    const char     *pszName;
+    /** The process nice value. */
+    int             iNice;
+    /** The delta applied to the iPriority value. */
+    int             iDelta;
+    /** Array scheduler attributes corresponding to each of the thread types. */
+    const PROCPRIORITYTYPE *paTypes;
+} PROCPRIORITY;
+
+
+/**
+ * Saved priority settings
+ */
+typedef struct
+{
+    /** Process priority. */
+    int                 iPriority;
+    /** Process level. */
+    struct sched_param  SchedParam;
+    /** Process level. */
+    int                 iPolicy;
+    /** pthread level. */
+    struct sched_param  PthreadSchedParam;
+    /** pthread level. */
+    int                 iPthreadPolicy;
+} SAVEDPRIORITY, *PSAVEDPRIORITY;
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+/**
+ * Thread level priorities based on a 0..31 priority range
+ * as specified as the minimum for SCHED_RR/FIFO. FreeBSD
+ * seems to be using this (needs more research to be
+ * certain).
+ */
+static const PROCPRIORITYTYPE g_aTypesThread[RTTHREADTYPE_END] =
+{
+    { RTTHREADTYPE_INVALID,                 -999999999 },
+    { RTTHREADTYPE_INFREQUENT_POLLER,        5 },
+    { RTTHREADTYPE_MAIN_HEAVY_WORKER,       12 },
+    { RTTHREADTYPE_EMULATION,               14 },
+    { RTTHREADTYPE_DEFAULT,                 15 },
+    { RTTHREADTYPE_GUI,                     16 },
+    { RTTHREADTYPE_MAIN_WORKER,             18 },
+    { RTTHREADTYPE_VRDP_IO,                 24 },
+    { RTTHREADTYPE_DEBUGGER,                28 },
+    { RTTHREADTYPE_MSG_PUMP,                29 },
+    { RTTHREADTYPE_IO,                      30 },
+    { RTTHREADTYPE_TIMER,                   31 }
+};
+
+static const PROCPRIORITYTYPE g_aTypesThreadFlat[RTTHREADTYPE_END] =
+{
+    { RTTHREADTYPE_INVALID,                 ~0 },
+    { RTTHREADTYPE_INFREQUENT_POLLER,       15 },
+    { RTTHREADTYPE_MAIN_HEAVY_WORKER,       15 },
+    { RTTHREADTYPE_EMULATION,               15 },
+    { RTTHREADTYPE_DEFAULT,                 15 },
+    { RTTHREADTYPE_GUI,                     15 },
+    { RTTHREADTYPE_MAIN_WORKER,             15 },
+    { RTTHREADTYPE_VRDP_IO,                 15 },
+    { RTTHREADTYPE_DEBUGGER,                15 },
+    { RTTHREADTYPE_MSG_PUMP,                15 },
+    { RTTHREADTYPE_IO,                      15 },
+    { RTTHREADTYPE_TIMER,                   15 }
+};
+
+/**
+ * Process and thread level priority, full access at thread level.
+ */
+static const PROCPRIORITY   g_aProcessAndThread[] =
+{
+    { RTPROCPRIORITY_FLAT,      "Flat",      0, 0, g_aTypesThreadFlat },
+    { RTPROCPRIORITY_LOW,       "Low",       9, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",      11, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",      15, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",      17, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",      19, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",       7, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",       5, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",       3, 0, g_aTypesThread },
+    { RTPROCPRIORITY_LOW,       "Low",       1, 0, g_aTypesThread },
+    { RTPROCPRIORITY_NORMAL,    "Normal",    0, 0, g_aTypesThread },
+    { RTPROCPRIORITY_NORMAL,    "Normal",    0, 0, g_aTypesThreadFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -9, 0, g_aTypesThread },
+    { RTPROCPRIORITY_HIGH,      "High",     -7, 0, g_aTypesThread },
+    { RTPROCPRIORITY_HIGH,      "High",     -5, 0, g_aTypesThread },
+    { RTPROCPRIORITY_HIGH,      "High",     -3, 0, g_aTypesThread },
+    { RTPROCPRIORITY_HIGH,      "High",     -1, 0, g_aTypesThread },
+    { RTPROCPRIORITY_HIGH,      "High",     -9, 0, g_aTypesThreadFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -1, 0, g_aTypesThreadFlat }
+};
+
+/**
+ * Deltas for a process in which we are not restricted
+ * to only be lowering the priority.
+ */
+static const PROCPRIORITYTYPE g_aTypesUnixFree[RTTHREADTYPE_END] =
+{
+    { RTTHREADTYPE_INVALID,                 -999999999 },
+    { RTTHREADTYPE_INFREQUENT_POLLER,       +3 },
+    { RTTHREADTYPE_MAIN_HEAVY_WORKER,       +2 },
+    { RTTHREADTYPE_EMULATION,               +1 },
+    { RTTHREADTYPE_DEFAULT,                  0 },
+    { RTTHREADTYPE_GUI,                      0 },
+    { RTTHREADTYPE_MAIN_WORKER,              0 },
+    { RTTHREADTYPE_VRDP_IO,                 -1 },
+    { RTTHREADTYPE_DEBUGGER,                -1 },
+    { RTTHREADTYPE_MSG_PUMP,                -2 },
+    { RTTHREADTYPE_IO,                      -3 },
+    { RTTHREADTYPE_TIMER,                   -4 }
+};
+
+/**
+ * Deltas for a process in which we are restricted
+ * to only be lowering the priority.
+ */
+static const PROCPRIORITYTYPE g_aTypesUnixRestricted[RTTHREADTYPE_END] =
+{
+    { RTTHREADTYPE_INVALID,                 -999999999 },
+    { RTTHREADTYPE_INFREQUENT_POLLER,       +3 },
+    { RTTHREADTYPE_MAIN_HEAVY_WORKER,       +2 },
+    { RTTHREADTYPE_EMULATION,               +1 },
+    { RTTHREADTYPE_DEFAULT,                  0 },
+    { RTTHREADTYPE_GUI,                      0 },
+    { RTTHREADTYPE_MAIN_WORKER,              0 },
+    { RTTHREADTYPE_VRDP_IO,                  0 },
+    { RTTHREADTYPE_DEBUGGER,                 0 },
+    { RTTHREADTYPE_MSG_PUMP,                 0 },
+    { RTTHREADTYPE_IO,                       0 },
+    { RTTHREADTYPE_TIMER,                    0 }
+};
+
+/**
+ * Deltas for a process in which we are restricted
+ * to only be lowering the priority.
+ */
+static const PROCPRIORITYTYPE g_aTypesUnixFlat[RTTHREADTYPE_END] =
+{
+    { RTTHREADTYPE_INVALID,                 -999999999 },
+    { RTTHREADTYPE_INFREQUENT_POLLER,        0 },
+    { RTTHREADTYPE_MAIN_HEAVY_WORKER,        0 },
+    { RTTHREADTYPE_EMULATION,                0 },
+    { RTTHREADTYPE_DEFAULT,                  0 },
+    { RTTHREADTYPE_GUI,                      0 },
+    { RTTHREADTYPE_MAIN_WORKER,              0 },
+    { RTTHREADTYPE_VRDP_IO,                  0 },
+    { RTTHREADTYPE_DEBUGGER,                 0 },
+    { RTTHREADTYPE_MSG_PUMP,                 0 },
+    { RTTHREADTYPE_IO,                       0 },
+    { RTTHREADTYPE_TIMER,                    0 }
+};
+
+/**
+ * Process and thread level priority, full access at thread level.
+ */
+static const PROCPRIORITY   g_aUnixConfigs[] =
+{
+    { RTPROCPRIORITY_FLAT,      "Flat",      0,   0, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_LOW,       "Low",       9,   9, g_aTypesUnixFree },
+    { RTPROCPRIORITY_LOW,       "Low",       9,   9, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_LOW,       "Low",      15,  15, g_aTypesUnixFree },
+    { RTPROCPRIORITY_LOW,       "Low",      15,  15, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_LOW,       "Low",      17,  17, g_aTypesUnixFree },
+    { RTPROCPRIORITY_LOW,       "Low",      17,  17, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_LOW,       "Low",      19,  19, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_LOW,       "Low",       9,   9, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_LOW,       "Low",      15,  15, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_LOW,       "Low",      17,  17, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_NORMAL,    "Normal",    0,   0, g_aTypesUnixFree },
+    { RTPROCPRIORITY_NORMAL,    "Normal",    0,   0, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_NORMAL,    "Normal",    0,   0, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -9,  -9, g_aTypesUnixFree },
+    { RTPROCPRIORITY_HIGH,      "High",     -7,  -7, g_aTypesUnixFree },
+    { RTPROCPRIORITY_HIGH,      "High",     -5,  -5, g_aTypesUnixFree },
+    { RTPROCPRIORITY_HIGH,      "High",     -3,  -3, g_aTypesUnixFree },
+    { RTPROCPRIORITY_HIGH,      "High",     -1,  -1, g_aTypesUnixFree },
+    { RTPROCPRIORITY_HIGH,      "High",     -9,  -9, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_HIGH,      "High",     -7,  -7, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_HIGH,      "High",     -5,  -5, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_HIGH,      "High",     -3,  -3, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_HIGH,      "High",     -1,  -1, g_aTypesUnixRestricted },
+    { RTPROCPRIORITY_HIGH,      "High",     -9,  -9, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -7,  -7, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -5,  -5, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -3,  -3, g_aTypesUnixFlat },
+    { RTPROCPRIORITY_HIGH,      "High",     -1,  -1, g_aTypesUnixFlat }
+};
+
+/**
+ * The dynamic default priority configuration.
+ *
+ * This will be recalulated at runtime depending on what the
+ * system allow us to do and what the current priority is.
+ */
+static PROCPRIORITY g_aDefaultPriority =
+{
+    RTPROCPRIORITY_LOW, "Default", 0, 0, g_aTypesUnixRestricted
+};
+
+/** Pointer to the current priority configuration. */
+static const PROCPRIORITY *g_pProcessPriority = &g_aDefaultPriority;
+
+
+/** Set to what kind of scheduling priority support the host
+ * OS seems to be offering. Determined at runtime.
+ */
+static enum
+{
+    OSPRIOSUP_UNDETERMINED = 0,
+    /** An excellent combination of process and thread level
+     * I.e. setpriority() works on process level, one have to be supervisor
+     * to raise priority as is the custom in unix. While pthread_setschedparam()
+     * works on thread level and we can raise the priority just like we want.
+     *
+     * I think this is what FreeBSD offers. (It is certainly analogous to what
+     * NT offers if you wondered.) Linux on the other hand doesn't provide this
+     * for processes with SCHED_OTHER policy, and I'm not sure if we want to
+     * play around with using the real-time SCHED_RR and SCHED_FIFO which would
+     * require special privileges anyway.
+     */
+    OSPRIOSUP_PROCESS_AND_THREAD_LEVEL,
+    /** A rough thread level priority only.
+     * setpriority() is the only real game in town, and it works on thread level.
+     */
+    OSPRIOSUP_THREAD_LEVEL
+}   volatile g_enmOsPrioSup = OSPRIOSUP_UNDETERMINED;
+
+/** Set if we figure we have nice capability, meaning we can use setpriority
+ * to raise the priority. */
+static bool g_fCanNice = false;
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+
+
+/**
+ * Saves all the scheduling attributes we can think of.
+ */
+static void rtSchedNativeSave(PSAVEDPRIORITY pSave)
+{
+    memset(pSave, 0xff, sizeof(*pSave));
+
+    errno = 0;
+    pSave->iPriority = getpriority(PRIO_PROCESS, 0 /* current process */);
+    Assert(errno == 0);
+
+    errno = 0;
+    sched_getparam(0 /* current process */, &pSave->SchedParam);
+    Assert(errno == 0);
+
+    errno = 0;
+    pSave->iPolicy = sched_getscheduler(0 /* current process */);
+    Assert(errno == 0);
+
+    int rc = pthread_getschedparam(pthread_self(), &pSave->iPthreadPolicy, &pSave->PthreadSchedParam);
+    Assert(rc == 0); NOREF(rc);
+}
+
+
+/**
+ * Restores scheduling attributes.
+ * Most of this won't work right, but anyway...
+ */
+static void rtSchedNativeRestore(PSAVEDPRIORITY pSave)
+{
+    setpriority(PRIO_PROCESS, 0, pSave->iPriority);
+    sched_setscheduler(0, pSave->iPolicy, &pSave->SchedParam);
+    sched_setparam(0, &pSave->SchedParam);
+    pthread_setschedparam(pthread_self(), pSave->iPthreadPolicy, &pSave->PthreadSchedParam);
+}
+
+
+/**
+ * Starts a worker thread and wait for it to complete.
+ * We cannot use RTThreadCreate since we're already owner of the RW lock.
+ */
+static int rtSchedCreateThread(void *(*pfnThread)(void *pvArg), void *pvArg)
+{
+    /*
+     * Setup thread attributes.
+     */
+    pthread_attr_t  ThreadAttr;
+    int rc = pthread_attr_init(&ThreadAttr);
+    if (!rc)
+    {
+        rc = pthread_attr_setdetachstate(&ThreadAttr, PTHREAD_CREATE_JOINABLE);
+        if (!rc)
+        {
+            rc = pthread_attr_setstacksize(&ThreadAttr, 128*1024);
+            if (!rc)
+            {
+                /*
+                 * Create the thread.
+                 */
+                pthread_t Thread;
+                rc = pthread_create(&Thread, &ThreadAttr, pfnThread, pvArg);
+                if (!rc)
+                {
+                    pthread_attr_destroy(&ThreadAttr);
+                    /*
+                     * Wait for the thread to finish.
+                     */
+                    void *pvRet = (void *)-1;
+                    do
+                    {
+                        rc = pthread_join(Thread, &pvRet);
+                    } while (rc == EINTR);
+                    if (rc)
+                        return RTErrConvertFromErrno(rc);
+                    return (int)(uintptr_t)pvRet;
+                }
+            }
+        }
+        pthread_attr_destroy(&ThreadAttr);
+    }
+    return RTErrConvertFromErrno(rc);
+}
+
+
+static void rtSchedDumpPriority(void)
+{
+#ifdef THREAD_LOGGING
+    Log(("Priority: g_fCanNice=%d g_enmOsPrioSup=%d\n", g_fCanNice, g_enmOsPrioSup));
+    Log(("Priority: enmPriority=%d \"%s\" iNice=%d iDelta=%d\n",
+         g_pProcessPriority->enmPriority,
+         g_pProcessPriority->pszName,
+         g_pProcessPriority->iNice,
+         g_pProcessPriority->iDelta));
+    Log(("Priority:  %2d INFREQUENT_POLLER = %d\n", RTTHREADTYPE_INFREQUENT_POLLER, g_pProcessPriority->paTypes[RTTHREADTYPE_INFREQUENT_POLLER].iPriority));
+    Log(("Priority:  %2d MAIN_HEAVY_WORKER = %d\n", RTTHREADTYPE_MAIN_HEAVY_WORKER, g_pProcessPriority->paTypes[RTTHREADTYPE_MAIN_HEAVY_WORKER].iPriority));
+    Log(("Priority:  %2d EMULATION         = %d\n", RTTHREADTYPE_EMULATION        , g_pProcessPriority->paTypes[RTTHREADTYPE_EMULATION        ].iPriority));
+    Log(("Priority:  %2d DEFAULT           = %d\n", RTTHREADTYPE_DEFAULT          , g_pProcessPriority->paTypes[RTTHREADTYPE_DEFAULT          ].iPriority));
+    Log(("Priority:  %2d GUI               = %d\n", RTTHREADTYPE_GUI              , g_pProcessPriority->paTypes[RTTHREADTYPE_GUI              ].iPriority));
+    Log(("Priority:  %2d MAIN_WORKER       = %d\n", RTTHREADTYPE_MAIN_WORKER      , g_pProcessPriority->paTypes[RTTHREADTYPE_MAIN_WORKER      ].iPriority));
+    Log(("Priority:  %2d VRDP_IO           = %d\n", RTTHREADTYPE_VRDP_IO          , g_pProcessPriority->paTypes[RTTHREADTYPE_VRDP_IO          ].iPriority));
+    Log(("Priority:  %2d DEBUGGER          = %d\n", RTTHREADTYPE_DEBUGGER         , g_pProcessPriority->paTypes[RTTHREADTYPE_DEBUGGER         ].iPriority));
+    Log(("Priority:  %2d MSG_PUMP          = %d\n", RTTHREADTYPE_MSG_PUMP         , g_pProcessPriority->paTypes[RTTHREADTYPE_MSG_PUMP         ].iPriority));
+    Log(("Priority:  %2d IO                = %d\n", RTTHREADTYPE_IO               , g_pProcessPriority->paTypes[RTTHREADTYPE_IO               ].iPriority));
+    Log(("Priority:  %2d TIMER             = %d\n", RTTHREADTYPE_TIMER            , g_pProcessPriority->paTypes[RTTHREADTYPE_TIMER            ].iPriority));
+#endif
+}
+
+
+/**
+ * The prober thread.
+ * We don't want to mess with the priority of the calling thread.
+ *
+ * @remark  This is pretty presumptive stuff, but if it works on Linux and
+ *          FreeBSD it does what I want.
+ */
+static void *rtSchedNativeProberThread(void *pvUser)
+{
+    SAVEDPRIORITY SavedPriority;
+    rtSchedNativeSave(&SavedPriority);
+
+    /*
+     * Let's first try and see what we get on a thread level.
+     */
+    int iMax = sched_get_priority_max(SavedPriority.iPthreadPolicy);
+    int iMin = sched_get_priority_min(SavedPriority.iPthreadPolicy);
+    if (iMax - iMin >= 32)
+    {
+        pthread_t Self = pthread_self();
+        int i = iMin;
+        while (i <= iMax)
+        {
+            struct sched_param SchedParam = SavedPriority.PthreadSchedParam;
+            SchedParam.sched_priority = i;
+            if (pthread_setschedparam(Self, SavedPriority.iPthreadPolicy, &SchedParam))
+                break;
+            i++;
+        }
+        if (i == iMax)
+            g_enmOsPrioSup = OSPRIOSUP_PROCESS_AND_THREAD_LEVEL;
+    }
+
+    /*
+     * Ok, we didn't have the good stuff, so let's fall back on the unix stuff.
+     */
+    if (g_enmOsPrioSup == OSPRIOSUP_UNDETERMINED)
+        g_enmOsPrioSup = OSPRIOSUP_THREAD_LEVEL;
+
+    /*
+     * Check if we can get higher priority (typically only root can do this).
+     * (Won't work right if our priority is -19 to start with, but what the heck.)
+     *
+     * We assume that the unix priority is -19 to 19. I know there are defines
+     * for this, but I don't remember which and if I'm awake enough to make sense
+     * of them from any SuS spec.
+     */
+    int iStart = getpriority(PRIO_PROCESS, 0);
+    int i = iStart;
+    while (i-- > -19)
+    {
+        if (setpriority(PRIO_PROCESS, 0, i))
+            break;
+    }
+    if (getpriority(PRIO_PROCESS, 0) != iStart)
+        g_fCanNice = true;
+    else
+        g_fCanNice = false;
+
+    /* done */
+    rtSchedNativeRestore(&SavedPriority);
+    RT_NOREF(pvUser);
+    return (void *)VINF_SUCCESS;
+}
+
+
+/**
+ * Calculate the scheduling properties for all the threads in the default
+ * process priority, assuming the current thread have the type enmType.
+ *
+ * @returns iprt status code.
+ * @param   enmType     The thread type to be assumed for the current thread.
+ */
+DECLHIDDEN(int) rtSchedNativeCalcDefaultPriority(RTTHREADTYPE enmType)
+{
+    Assert(enmType > RTTHREADTYPE_INVALID && enmType < RTTHREADTYPE_END);
+
+    /*
+     * First figure out what's supported by the OS.
+     */
+    if (g_enmOsPrioSup == OSPRIOSUP_UNDETERMINED)
+    {
+        int iPriority = getpriority(PRIO_PROCESS, 0);
+        int rc = rtSchedCreateThread(rtSchedNativeProberThread, NULL);
+        if (RT_FAILURE(rc))
+            return rc;
+        if (g_enmOsPrioSup == OSPRIOSUP_UNDETERMINED)
+            g_enmOsPrioSup = OSPRIOSUP_THREAD_LEVEL;
+        Assert(getpriority(PRIO_PROCESS, 0) == iPriority); NOREF(iPriority);
+    }
+
+    /*
+     * Now let's see what we can do...
+     */
+    int iPriority = getpriority(PRIO_PROCESS, 0);
+    switch (g_enmOsPrioSup)
+    {
+        case OSPRIOSUP_PROCESS_AND_THREAD_LEVEL:
+        {
+            g_aDefaultPriority.iNice = iPriority;
+            g_aDefaultPriority.iDelta = 0;
+            g_aDefaultPriority.paTypes = g_aTypesThread;
+            Assert(enmType == g_aDefaultPriority.paTypes[enmType].enmType);
+            break;
+        }
+
+        case OSPRIOSUP_THREAD_LEVEL:
+        {
+            if (g_fCanNice)
+                g_aDefaultPriority.paTypes = g_aTypesUnixFree;
+            else
+                g_aDefaultPriority.paTypes = g_aTypesUnixRestricted;
+            Assert(enmType == g_aDefaultPriority.paTypes[enmType].enmType);
+            g_aDefaultPriority.iNice = iPriority - g_aDefaultPriority.paTypes[enmType].iPriority;
+            g_aDefaultPriority.iDelta = g_aDefaultPriority.iNice;
+            break;
+        }
+
+        default:
+            AssertFailed();
+            break;
+    }
+    rtSchedDumpPriority();
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * The validator thread.
+ * We don't want to mess with the priority of the calling thread.
+ *
+ * @remark  This is pretty presumptive stuff, but if it works on Linux and
+ *          FreeBSD it does what I want.
+ */
+static void *rtSchedNativeValidatorThread(void *pvUser)
+{
+    const PROCPRIORITY *pCfg = (const PROCPRIORITY *)pvUser;
+    SAVEDPRIORITY SavedPriority;
+    rtSchedNativeSave(&SavedPriority);
+
+    int rc = VINF_SUCCESS;
+    switch (g_enmOsPrioSup)
+    {
+        /*
+         * Try set the specified process priority and then try
+         * out all the thread priorities which are used.
+         */
+        case OSPRIOSUP_PROCESS_AND_THREAD_LEVEL:
+        {
+            if (!setpriority(PRIO_PROCESS, 0, pCfg->iNice))
+            {
+                int iMin = sched_get_priority_min(SavedPriority.iPolicy);
+                pthread_t Self = pthread_self();
+                for (int i = RTTHREADTYPE_INVALID + 1; i < RTTHREADTYPE_END; i++)
+                {
+                    struct sched_param SchedParam = SavedPriority.PthreadSchedParam;
+                    SchedParam.sched_priority = pCfg->paTypes[i].iPriority
+                        + pCfg->iDelta + iMin;
+                    rc = pthread_setschedparam(Self, SavedPriority.iPthreadPolicy, &SchedParam);
+                    if (rc)
+                    {
+                        rc = RTErrConvertFromErrno(rc);
+                        break;
+                    }
+                }
+            }
+            else
+                rc = RTErrConvertFromErrno(errno);
+            break;
+        }
+
+        /*
+         * Try out the priorities from the top and down.
+         */
+        case OSPRIOSUP_THREAD_LEVEL:
+        {
+            int i = RTTHREADTYPE_END;
+            while (--i > RTTHREADTYPE_INVALID)
+            {
+                int iPriority = pCfg->paTypes[i].iPriority + pCfg->iDelta;
+                if (setpriority(PRIO_PROCESS, 0, iPriority))
+                {
+                    rc = RTErrConvertFromErrno(errno);
+                    break;
+                }
+            }
+            break;
+        }
+
+        default:
+            AssertFailed();
+            break;
+    }
+
+    /* done */
+    rtSchedNativeRestore(&SavedPriority);
+    return (void *)(intptr_t)rc;
+}
+
+
+DECLHIDDEN(int) rtProcNativeSetPriority(RTPROCPRIORITY enmPriority)
+{
+    Assert(enmPriority > RTPROCPRIORITY_INVALID && enmPriority < RTPROCPRIORITY_LAST);
+
+#ifdef RTTHREAD_POSIX_WITH_CREATE_PRIORITY_PROXY
+    /*
+     * Make sure the proxy creation thread is started so we don't 'lose' our
+     * initial priority if it's lowered.
+     */
+    rtThreadPosixPriorityProxyStart();
+#endif
+
+    /*
+     * Nothing to validate for the default priority (assuming no external renice).
+     */
+    int rc = VINF_SUCCESS;
+    if (enmPriority == RTPROCPRIORITY_DEFAULT)
+        g_pProcessPriority = &g_aDefaultPriority;
+    else
+    {
+        /*
+         * Select the array to search.
+         */
+        const PROCPRIORITY *pa;
+        unsigned            c;
+        switch (g_enmOsPrioSup)
+        {
+            case OSPRIOSUP_PROCESS_AND_THREAD_LEVEL:
+                pa = g_aProcessAndThread;
+                c = RT_ELEMENTS(g_aProcessAndThread);
+                break;
+            case OSPRIOSUP_THREAD_LEVEL:
+                pa = g_aUnixConfigs;
+                c = RT_ELEMENTS(g_aUnixConfigs);
+                break;
+            default:
+                pa = NULL;
+                c = 0;
+                break;
+        }
+
+        /*
+         * Search the array.
+         */
+        rc = VERR_FILE_NOT_FOUND;
+        unsigned i;
+        for (i = 0; i < c; i++)
+        {
+            if (pa[i].enmPriority == enmPriority)
+            {
+                /*
+                 * Validate it.
+                 */
+                int iPriority = getpriority(PRIO_PROCESS, 0);
+                int rc3 = rtSchedCreateThread(rtSchedNativeValidatorThread, (void *)&pa[i]);
+                Assert(getpriority(PRIO_PROCESS, 0) == iPriority); NOREF(iPriority);
+                if (RT_SUCCESS(rc))
+                    rc = rc3;
+                if (RT_SUCCESS(rc))
+                    break;
+            }
+        }
+
+        /*
+         * Did we get lucky?
+         * If so update process priority and globals.
+         */
+        if (RT_SUCCESS(rc))
+        {
+            switch (g_enmOsPrioSup)
+            {
+                case OSPRIOSUP_PROCESS_AND_THREAD_LEVEL:
+                    if (setpriority(PRIO_PROCESS, 0, pa[i].iNice))
+                    {
+                        rc = RTErrConvertFromErrno(errno);
+                        AssertMsgFailed(("setpriority(,,%d) -> errno=%d rc=%Rrc\n", pa[i].iNice, errno, rc));
+                    }
+                    break;
+
+                default:
+                    break;
+            }
+
+            if (RT_SUCCESS(rc))
+                g_pProcessPriority = &pa[i];
+        }
+    }
+
+#ifdef THREAD_LOGGING
+    LogFlow(("rtProcNativeSetPriority: returns %Rrc enmPriority=%d\n", rc, enmPriority));
+    rtSchedDumpPriority();
+#endif
+    return rc;
+}
+
+
+/**
+ * Worker for rtThreadNativeSetPriority/OSPRIOSUP_PROCESS_AND_THREAD_LEVEL
+ * that's either called on the priority proxy thread or directly if no proxy.
+ */
+static DECLCALLBACK(int) rtThreadPosixSetPriorityOnProcAndThrdCallback(PRTTHREADINT pThread, RTTHREADTYPE enmType)
+{
+    struct sched_param  SchedParam = {-9999999};
+    int                 iPolicy = -7777777;
+    int rc = pthread_getschedparam((pthread_t)pThread->Core.Key, &iPolicy, &SchedParam);
+    if (!rc)
+    {
+        SchedParam.sched_priority = g_pProcessPriority->paTypes[enmType].iPriority
+            + g_pProcessPriority->iDelta
+            + sched_get_priority_min(iPolicy);
+
+        rc = pthread_setschedparam((pthread_t)pThread->Core.Key, iPolicy, &SchedParam);
+        if (!rc)
+        {
+#ifdef THREAD_LOGGING
+            Log(("rtThreadNativeSetPriority: Thread=%p enmType=%d iPolicy=%d sched_priority=%d pid=%d\n",
+                 pThread->Core.Key, enmType, iPolicy, SchedParam.sched_priority, getpid()));
+#endif
+            return VINF_SUCCESS;
+        }
+    }
+
+    int rcNative = rc;
+    rc = RTErrConvertFromErrno(rc);
+    AssertMsgFailed(("pthread_[gs]etschedparam(%p, %d, {%d}) -> rcNative=%d rc=%Rrc\n",
+                     (void *)pThread->Core.Key, iPolicy, SchedParam.sched_priority, rcNative, rc)); NOREF(rcNative);
+    return rc;
+}
+
+
+DECLHIDDEN(int) rtThreadNativeSetPriority(PRTTHREADINT pThread, RTTHREADTYPE enmType)
+{
+    Assert(enmType > RTTHREADTYPE_INVALID && enmType < RTTHREADTYPE_END);
+    Assert(enmType == g_pProcessPriority->paTypes[enmType].enmType);
+
+    int rc = VINF_SUCCESS;
+    switch (g_enmOsPrioSup)
+    {
+        case OSPRIOSUP_PROCESS_AND_THREAD_LEVEL:
+        {
+#ifdef RTTHREAD_POSIX_WITH_CREATE_PRIORITY_PROXY
+            if (rtThreadPosixPriorityProxyStart())
+                rc = rtThreadPosixPriorityProxyCall(pThread, (PFNRT)rtThreadPosixSetPriorityOnProcAndThrdCallback,
+                                                    2, pThread, enmType);
+            else
+#endif
+                rc = rtThreadPosixSetPriorityOnProcAndThrdCallback(pThread, enmType);
+            break;
+        }
+
+        case OSPRIOSUP_THREAD_LEVEL:
+        {
+            /* No cross platform way of getting the 'who' parameter value for
+               arbitrary threads, so this is restricted to the calling thread only. */
+            AssertReturn((pthread_t)pThread->Core.Key == pthread_self(), VERR_NOT_SUPPORTED);
+
+            int iPriority = g_pProcessPriority->paTypes[enmType].iPriority + g_pProcessPriority->iDelta;
+            if (!setpriority(PRIO_PROCESS, 0, iPriority))
+            {
+                AssertMsg(iPriority == getpriority(PRIO_PROCESS, 0), ("iPriority=%d getpriority()=%d\n", iPriority, getpriority(PRIO_PROCESS, 0)));
+#ifdef THREAD_LOGGING
+                Log(("rtThreadNativeSetPriority: Thread=%p enmType=%d iPriority=%d pid=%d\n", pThread->Core.Key, enmType, iPriority, getpid()));
+#endif
+            }
+            else
+            {
+#if 0
+                rc = RTErrConvertFromErrno(errno);
+                AssertMsgFailed(("setpriority(,, %d) -> errno=%d rc=%Rrc\n", iPriority, errno, rc));
+#else
+                /** @todo
+                 * Just keep quiet about failures now - we'll fail here because we're not
+                 * allowed to raise our own priority. This is a problem when starting the
+                 * threads with higher priority from EMT (i.e. most threads it starts).
+                 * This is apparently inherited from the parent in some cases and not
+                 * in other cases. I guess this would come down to which kind of pthread
+                 * implementation is actually in use, and how many sensible patches which
+                 * are installed.
+                 * I need to find a system where this problem shows up in order to come up
+                 * with a proper fix. There's an pthread_create attribute for not inheriting
+                 * scheduler stuff I think...
+                 */
+                rc = VINF_SUCCESS;
+#endif
+            }
+            break;
+        }
+
+        /*
+         * Any thread created before we determine the default config, remains unchanged!
+         * The prober thread above is one of those.
+         */
+        default:
+            break;
+    }
+
+    return rc;
+}
+