initial commit, 4.5 stable

thirdparty/sdl/core/linux/SDL_threadprio.c

@@ -0,0 +1,345 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "SDL_internal.h"
+
+#ifdef SDL_PLATFORM_LINUX
+
+#ifndef SDL_THREADS_DISABLED
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <pthread.h>
+#include <sched.h>
+#include <unistd.h>
+
+// RLIMIT_RTTIME requires kernel >= 2.6.25 and is in glibc >= 2.14
+#ifndef RLIMIT_RTTIME
+#define RLIMIT_RTTIME 15
+#endif
+// SCHED_RESET_ON_FORK is in kernel >= 2.6.32.
+#ifndef SCHED_RESET_ON_FORK
+#define SCHED_RESET_ON_FORK 0x40000000
+#endif
+
+#include "SDL_dbus.h"
+
+#ifdef SDL_USE_LIBDBUS
+
+// d-bus queries to org.freedesktop.RealtimeKit1.
+#define RTKIT_DBUS_NODE      "org.freedesktop.RealtimeKit1"
+#define RTKIT_DBUS_PATH      "/org/freedesktop/RealtimeKit1"
+#define RTKIT_DBUS_INTERFACE "org.freedesktop.RealtimeKit1"
+
+// d-bus queries to the XDG portal interface to RealtimeKit1
+#define XDG_PORTAL_DBUS_NODE      "org.freedesktop.portal.Desktop"
+#define XDG_PORTAL_DBUS_PATH      "/org/freedesktop/portal/desktop"
+#define XDG_PORTAL_DBUS_INTERFACE "org.freedesktop.portal.Realtime"
+
+static bool rtkit_use_session_conn;
+static const char *rtkit_dbus_node;
+static const char *rtkit_dbus_path;
+static const char *rtkit_dbus_interface;
+
+static pthread_once_t rtkit_initialize_once = PTHREAD_ONCE_INIT;
+static Sint32 rtkit_min_nice_level = -20;
+static Sint32 rtkit_max_realtime_priority = 99;
+static Sint64 rtkit_max_rttime_usec = 200000;
+
+/*
+ * Checking that the RTTimeUSecMax property exists and is an int64 confirms that:
+ *  - The desktop portal exists and supports the realtime interface.
+ *  - The realtime interface is new enough to have the required bug fixes applied.
+ */
+static bool realtime_portal_supported(DBusConnection *conn)
+{
+    Sint64 res;
+    return SDL_DBus_QueryPropertyOnConnection(conn, XDG_PORTAL_DBUS_NODE, XDG_PORTAL_DBUS_PATH, XDG_PORTAL_DBUS_INTERFACE,
+                                              "RTTimeUSecMax", DBUS_TYPE_INT64, &res);
+}
+
+static void set_rtkit_interface(void)
+{
+    SDL_DBusContext *dbus = SDL_DBus_GetContext();
+
+    // xdg-desktop-portal works in all instances, so check for it first.
+    if (dbus && realtime_portal_supported(dbus->session_conn)) {
+        rtkit_use_session_conn = true;
+        rtkit_dbus_node = XDG_PORTAL_DBUS_NODE;
+        rtkit_dbus_path = XDG_PORTAL_DBUS_PATH;
+        rtkit_dbus_interface = XDG_PORTAL_DBUS_INTERFACE;
+    } else { // Fall back to the standard rtkit interface in all other cases.
+        rtkit_use_session_conn = false;
+        rtkit_dbus_node = RTKIT_DBUS_NODE;
+        rtkit_dbus_path = RTKIT_DBUS_PATH;
+        rtkit_dbus_interface = RTKIT_DBUS_INTERFACE;
+    }
+}
+
+static DBusConnection *get_rtkit_dbus_connection(void)
+{
+    SDL_DBusContext *dbus = SDL_DBus_GetContext();
+
+    if (dbus) {
+        return rtkit_use_session_conn ? dbus->session_conn : dbus->system_conn;
+    }
+
+    return NULL;
+}
+
+static void rtkit_initialize(void)
+{
+    DBusConnection *dbus_conn;
+
+    set_rtkit_interface();
+    dbus_conn = get_rtkit_dbus_connection();
+
+    // Try getting minimum nice level: this is often greater than PRIO_MIN (-20).
+    if (!dbus_conn || !SDL_DBus_QueryPropertyOnConnection(dbus_conn, rtkit_dbus_node, rtkit_dbus_path, rtkit_dbus_interface, "MinNiceLevel",
+                                                                 DBUS_TYPE_INT32, &rtkit_min_nice_level)) {
+        rtkit_min_nice_level = -20;
+    }
+
+    // Try getting maximum realtime priority: this can be less than the POSIX default (99).
+    if (!dbus_conn || !SDL_DBus_QueryPropertyOnConnection(dbus_conn, rtkit_dbus_node, rtkit_dbus_path, rtkit_dbus_interface, "MaxRealtimePriority",
+                                                                 DBUS_TYPE_INT32, &rtkit_max_realtime_priority)) {
+        rtkit_max_realtime_priority = 99;
+    }
+
+    // Try getting maximum rttime allowed by rtkit: exceeding this value will result in SIGKILL
+    if (!dbus_conn || !SDL_DBus_QueryPropertyOnConnection(dbus_conn, rtkit_dbus_node, rtkit_dbus_path, rtkit_dbus_interface, "RTTimeUSecMax",
+                                                                 DBUS_TYPE_INT64, &rtkit_max_rttime_usec)) {
+        rtkit_max_rttime_usec = 200000;
+    }
+}
+
+static bool rtkit_initialize_realtime_thread(void)
+{
+    // Following is an excerpt from rtkit README that outlines the requirements
+    // a thread must meet before making rtkit requests:
+    //
+    //   * Only clients with RLIMIT_RTTIME set will get RT scheduling
+    //
+    //   * RT scheduling will only be handed out to processes with
+    //     SCHED_RESET_ON_FORK set to guarantee that the scheduling
+    //     settings cannot 'leak' to child processes, thus making sure
+    //     that 'RT fork bombs' cannot be used to bypass RLIMIT_RTTIME
+    //     and take the system down.
+    //
+    //   * Limits are enforced on all user controllable resources, only
+    //     a maximum number of users, processes, threads can request RT
+    //     scheduling at the same time.
+    //
+    //   * Only a limited number of threads may be made RT in a
+    //     specific time frame.
+    //
+    //   * Client authorization is verified with PolicyKit
+
+    int err;
+    struct rlimit rlimit;
+    int nLimit = RLIMIT_RTTIME;
+    pid_t nPid = 0; // self
+    int nSchedPolicy = sched_getscheduler(nPid) | SCHED_RESET_ON_FORK;
+    struct sched_param schedParam;
+
+    SDL_zero(schedParam);
+
+    // Requirement #1: Set RLIMIT_RTTIME
+    err = getrlimit(nLimit, &rlimit);
+    if (err) {
+        return false;
+    }
+
+    // Current rtkit allows a max of 200ms right now
+    rlimit.rlim_max = rtkit_max_rttime_usec;
+    rlimit.rlim_cur = rlimit.rlim_max / 2;
+    err = setrlimit(nLimit, &rlimit);
+    if (err) {
+        return false;
+    }
+
+    // Requirement #2: Add SCHED_RESET_ON_FORK to the scheduler policy
+    err = sched_getparam(nPid, &schedParam);
+    if (err) {
+        return false;
+    }
+
+    err = sched_setscheduler(nPid, nSchedPolicy, &schedParam);
+    if (err) {
+        return false;
+    }
+
+    return true;
+}
+
+static bool rtkit_setpriority_nice(pid_t thread, int nice_level)
+{
+    DBusConnection *dbus_conn;
+    Uint64 pid = (Uint64)getpid();
+    Uint64 tid = (Uint64)thread;
+    Sint32 nice = (Sint32)nice_level;
+
+    pthread_once(&rtkit_initialize_once, rtkit_initialize);
+    dbus_conn = get_rtkit_dbus_connection();
+
+    if (nice < rtkit_min_nice_level) {
+        nice = rtkit_min_nice_level;
+    }
+
+    if (!dbus_conn || !SDL_DBus_CallMethodOnConnection(dbus_conn,
+                                                              rtkit_dbus_node, rtkit_dbus_path, rtkit_dbus_interface, "MakeThreadHighPriorityWithPID",
+                                                              DBUS_TYPE_UINT64, &pid, DBUS_TYPE_UINT64, &tid, DBUS_TYPE_INT32, &nice, DBUS_TYPE_INVALID,
+                                                              DBUS_TYPE_INVALID)) {
+        return false;
+    }
+    return true;
+}
+
+static bool rtkit_setpriority_realtime(pid_t thread, int rt_priority)
+{
+    DBusConnection *dbus_conn;
+    Uint64 pid = (Uint64)getpid();
+    Uint64 tid = (Uint64)thread;
+    Uint32 priority = (Uint32)rt_priority;
+
+    pthread_once(&rtkit_initialize_once, rtkit_initialize);
+    dbus_conn = get_rtkit_dbus_connection();
+
+    if (priority > rtkit_max_realtime_priority) {
+        priority = rtkit_max_realtime_priority;
+    }
+
+    // We always perform the thread state changes necessary for rtkit.
+    // This wastes some system calls if the state is already set but
+    // typically code sets a thread priority and leaves it so it's
+    // not expected that this wasted effort will be an issue.
+    // We also do not quit if this fails, we let the rtkit request
+    // go through to determine whether it really needs to fail or not.
+    rtkit_initialize_realtime_thread();
+
+    if (!dbus_conn || !SDL_DBus_CallMethodOnConnection(dbus_conn,
+                                                              rtkit_dbus_node, rtkit_dbus_path, rtkit_dbus_interface, "MakeThreadRealtimeWithPID",
+                                                              DBUS_TYPE_UINT64, &pid, DBUS_TYPE_UINT64, &tid, DBUS_TYPE_UINT32, &priority, DBUS_TYPE_INVALID,
+                                                              DBUS_TYPE_INVALID)) {
+        return false;
+    }
+    return true;
+}
+#else
+
+#define rtkit_max_realtime_priority 99
+
+#endif // dbus
+#endif // threads
+
+// this is a public symbol, so it has to exist even if threads are disabled.
+bool SDL_SetLinuxThreadPriority(Sint64 threadID, int priority)
+{
+#ifdef SDL_THREADS_DISABLED
+    return SDL_Unsupported();
+#else
+    if (setpriority(PRIO_PROCESS, (id_t)threadID, priority) == 0) {
+        return true;
+    }
+
+#ifdef SDL_USE_LIBDBUS
+    /* Note that this fails you most likely:
+         * Have your process's scheduler incorrectly configured.
+           See the requirements at:
+           http://git.0pointer.net/rtkit.git/tree/README#n16
+         * Encountered dbus/polkit security restrictions. Note
+           that the RealtimeKit1 dbus endpoint is inaccessible
+           over ssh connections for most common distro configs.
+           You might want to check your local config for details:
+           /usr/share/polkit-1/actions/org.freedesktop.RealtimeKit1.policy
+
+       README and sample code at: http://git.0pointer.net/rtkit.git
+    */
+    if (rtkit_setpriority_nice((pid_t)threadID, priority)) {
+        return true;
+    }
+#endif
+
+    return SDL_SetError("setpriority() failed");
+#endif
+}
+
+// this is a public symbol, so it has to exist even if threads are disabled.
+bool SDL_SetLinuxThreadPriorityAndPolicy(Sint64 threadID, int sdlPriority, int schedPolicy)
+{
+#ifdef SDL_THREADS_DISABLED
+    return SDL_Unsupported();
+#else
+    int osPriority;
+
+    if (schedPolicy == SCHED_RR || schedPolicy == SCHED_FIFO) {
+        if (sdlPriority == SDL_THREAD_PRIORITY_LOW) {
+            osPriority = 1;
+        } else if (sdlPriority == SDL_THREAD_PRIORITY_HIGH) {
+            osPriority = rtkit_max_realtime_priority * 3 / 4;
+        } else if (sdlPriority == SDL_THREAD_PRIORITY_TIME_CRITICAL) {
+            osPriority = rtkit_max_realtime_priority;
+        } else {
+            osPriority = rtkit_max_realtime_priority / 2;
+        }
+    } else {
+        if (sdlPriority == SDL_THREAD_PRIORITY_LOW) {
+            osPriority = 19;
+        } else if (sdlPriority == SDL_THREAD_PRIORITY_HIGH) {
+            osPriority = -10;
+        } else if (sdlPriority == SDL_THREAD_PRIORITY_TIME_CRITICAL) {
+            osPriority = -20;
+        } else {
+            osPriority = 0;
+        }
+
+        if (setpriority(PRIO_PROCESS, (id_t)threadID, osPriority) == 0) {
+            return true;
+        }
+    }
+
+#ifdef SDL_USE_LIBDBUS
+    /* Note that this fails you most likely:
+     * Have your process's scheduler incorrectly configured.
+       See the requirements at:
+       http://git.0pointer.net/rtkit.git/tree/README#n16
+     * Encountered dbus/polkit security restrictions. Note
+       that the RealtimeKit1 dbus endpoint is inaccessible
+       over ssh connections for most common distro configs.
+       You might want to check your local config for details:
+       /usr/share/polkit-1/actions/org.freedesktop.RealtimeKit1.policy
+
+       README and sample code at: http://git.0pointer.net/rtkit.git
+    */
+    if (schedPolicy == SCHED_RR || schedPolicy == SCHED_FIFO) {
+        if (rtkit_setpriority_realtime((pid_t)threadID, osPriority)) {
+            return true;
+        }
+    } else {
+        if (rtkit_setpriority_nice((pid_t)threadID, osPriority)) {
+            return true;
+        }
+    }
+#endif
+
+    return SDL_SetError("setpriority() failed");
+#endif
+}
+
+#endif // SDL_PLATFORM_LINUX