Use Linux futex as JackSynchro

Includes optimizations for internal clients, but not enabled yet.

common/wscript

@@ -83,10 +83,10 @@ def build(bld):
             'JackDebugClient.cpp',
             'timestamps.c',
             '../posix/JackPosixThread.cpp',
-            '../posix/JackPosixSemaphore.cpp',
             '../posix/JackPosixProcessSync.cpp',
             '../posix/JackPosixMutex.cpp',
             '../posix/JackSocket.cpp',
+            '../linux/JackLinuxFutex.cpp',
             '../linux/JackLinuxTime.c',
             ]
         includes = ['../linux', '../posix'] + includes

linux/JackLinuxFutex.cpp

+/*
+Copyright (C) 2004-2008 Grame
+Copyright (C) 2016 Filipe Coelho
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+*/
+
+#include "JackLinuxFutex.h"
+#include "JackTools.h"
+#include "JackConstants.h"
+#include "JackError.h"
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <syscall.h>
+#include <linux/futex.h>
+
+namespace Jack
+{
+
+void JackLinuxFutex::BuildName(const char* client_name, const char* server_name, char* res, int size)
+{
+    char ext_client_name[SYNC_MAX_NAME_SIZE + 1];
+    JackTools::RewriteName(client_name, ext_client_name);
+    if (getenv("JACK_PROMISCUOUS_SERVER")) {
+        snprintf(res, size, "jack_sem.%s_%s", server_name, ext_client_name);
+    } else {
+        snprintf(res, size, "jack_sem.%d_%s_%s", JackTools::GetUID(), server_name, ext_client_name);
+    }
+}
+
+bool JackLinuxFutex::Signal()
+{
+    if (!fFutex) {
+        jack_error("JackLinuxFutex::Signal name = %s already deallocated!!", fName);
+        return false;
+    }
+
+    if (fFlush) {
+        return true;
+    }
+
+    if (! __sync_bool_compare_and_swap(&fFutex->futex, 0, 1))
+    {
+        // already unlocked, do not wake futex
+        if (! fFutex->internal) return true;
+    }
+
+    ::syscall(__NR_futex, fFutex, fFutex->internal ? FUTEX_WAKE_PRIVATE : FUTEX_WAKE, 1, NULL, NULL, 0);
+    return true;
+}
+
+bool JackLinuxFutex::SignalAll()
+{
+    return Signal();
+}
+
+bool JackLinuxFutex::Wait()
+{
+    if (!fFutex) {
+        jack_error("JackLinuxFutex::Wait name = %s already deallocated!!", fName);
+        return false;
+    }
+
+    if (fFutex->needsChange)
+    {
+        fFutex->needsChange = false;
+        fFutex->internal = !fFutex->internal;
+    }
+
+    for (;;)
+    {
+        if (__sync_bool_compare_and_swap(&fFutex->futex, 1, 0))
+            return true;
+
+        if (::syscall(__NR_futex, fFutex, fFutex->internal ? FUTEX_WAIT_PRIVATE : FUTEX_WAIT, 0, NULL, NULL, 0) != 0 && errno != EWOULDBLOCK)
+            return false;
+    }
+}
+
+bool JackLinuxFutex::TimedWait(long usec)
+{
+    if (!fFutex) {
+        jack_error("JackLinuxFutex::TimedWait name = %s already deallocated!!", fName);
+        return false;
+     }
+
+    if (fFutex->needsChange)
+    {
+        fFutex->needsChange = false;
+        fFutex->internal = !fFutex->internal;
+    }
+
+    const uint secs  =  usec / 1000000;
+    const int  nsecs = (usec % 1000000) * 1000;
+
+    const timespec timeout = { static_cast<time_t>(secs), nsecs };
+
+    for (;;)
+    {
+        if (__sync_bool_compare_and_swap(&fFutex->futex, 1, 0))
+            return true;
+
+        if (::syscall(__NR_futex, fFutex, fFutex->internal ? FUTEX_WAIT_PRIVATE : FUTEX_WAIT, 0, &timeout, NULL, 0) != 0 && errno != EWOULDBLOCK)
+            return false;
+    }
+}
+
+// Server side : publish the futex in the global namespace
+bool JackLinuxFutex::Allocate(const char* name, const char* server_name, int value, bool internal)
+{
+    BuildName(name, server_name, fName, sizeof(fName));
+    jack_log("JackLinuxFutex::Allocate name = %s val = %ld", fName, value);
+
+    if ((fSharedMem = shm_open(fName, O_CREAT | O_RDWR, 0777)) < 0) {
+        jack_error("Allocate: can't check in named futex name = %s err = %s", fName, strerror(errno));
+        return false;
+    }
+
+    ftruncate(fSharedMem, sizeof(FutexData));
+
+    if ((fFutex = (FutexData*)mmap(NULL, sizeof(FutexData), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED, fSharedMem, 0)) == NULL) {
+        jack_error("Allocate: can't check in named futex name = %s err = %s", fName, strerror(errno));
+        close(fSharedMem);
+        fSharedMem = -1;
+        shm_unlink(fName);
+        return false;
+    }
+
+    fPrivate = internal;
+
+    fFutex->futex = value;
+    fFutex->internal = internal;
+    fFutex->wasInternal = internal;
+    fFutex->needsChange = false;
+    fFutex->externalCount = 0;
+    return true;
+}
+
+// Client side : get the published futex from server
+bool JackLinuxFutex::Connect(const char* name, const char* server_name)
+{
+    BuildName(name, server_name, fName, sizeof(fName));
+    jack_log("JackLinuxFutex::Connect name = %s", fName);
+
+    // Temporary...
+    if (fFutex) {
+        jack_log("Already connected name = %s", name);
+        return true;
+    }
+
+    if ((fSharedMem = shm_open(fName, O_RDWR, 0)) < 0) {
+        jack_error("Connect: can't connect named futex name = %s err = %s", fName, strerror(errno));
+        return false;
+    }
+
+    if ((fFutex = (FutexData*)mmap(NULL, sizeof(FutexData), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED, fSharedMem, 0)) == NULL) {
+        jack_error("Connect: can't connect named futex name = %s err = %s", fName, strerror(errno));
+        close(fSharedMem);
+        fSharedMem = -1;
+        return false;
+    }
+
+    if (! fPrivate && fFutex->wasInternal)
+    {
+        const char* externalSync = getenv("JACK_INTERNAL_CLIENT_SYNC");
+
+        if (externalSync != NULL && strstr(fName, externalSync) != NULL && ++fFutex->externalCount == 1)
+        {
+            jack_error("Note: client %s running as external client temporarily", fName);
+            fFutex->needsChange = true;
+        }
+    }
+
+    return true;
+}
+
+bool JackLinuxFutex::ConnectInput(const char* name, const char* server_name)
+{
+    return Connect(name, server_name);
+}
+
+bool JackLinuxFutex::ConnectOutput(const char* name, const char* server_name)
+{
+    return Connect(name, server_name);
+}
+
+bool JackLinuxFutex::Disconnect()
+{
+    if (!fFutex) {
+        return true;
+    }
+
+    if (! fPrivate && fFutex->wasInternal)
+    {
+        const char* externalSync = getenv("JACK_INTERNAL_CLIENT_SYNC");
+
+        if (externalSync != NULL && strstr(fName, externalSync) != NULL && --fFutex->externalCount == 0)
+        {
+            jack_error("Note: client %s now running as internal client again", fName);
+            fFutex->needsChange = true;
+        }
+    }
+
+    munmap(fFutex, sizeof(FutexData));
+    fFutex = NULL;
+
+    close(fSharedMem);
+    fSharedMem = -1;
+    return true;
+}
+
+// Server side : destroy the futex
+void JackLinuxFutex::Destroy()
+{
+    if (!fFutex) {
+        return;
+    }
+
+    munmap(fFutex, sizeof(FutexData));
+    fFutex = NULL;
+
+    close(fSharedMem);
+    fSharedMem = -1;
+
+    shm_unlink(fName);
+}
+
+} // end of namespace
+

linux/JackLinuxFutex.h

+/*
+Copyright (C) 2004-2008 Grame
+Copyright (C) 2016 Filipe Coelho
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+*/
+
+#ifndef __JackLinuxFutex__
+#define __JackLinuxFutex__
+
+#include "JackSynchro.h"
+#include "JackCompilerDeps.h"
+#include <stddef.h>
+
+namespace Jack
+{
+
+/*!
+\brief Inter process synchronization using Linux futex.
+
+ Based on the JackPosixSemaphore class.
+ Adapted to work with linux futex to be as light as possible and also work in multiple architectures.
+
+ Adds a new 'MakePrivate' function that makes the sync happen in the local process only,
+ making it even faster for internal clients.
+*/
+
+class SERVER_EXPORT JackLinuxFutex : public detail::JackSynchro
+{
+
+    private:
+        struct FutexData {
+            int futex;         // futex, needs to be 1st member
+            bool internal;     // current internal state
+            bool wasInternal;  // initial internal state, only changes in allocate
+            bool needsChange;  // change state on next wait call
+            int externalCount; // how many external clients have connected
+        };
+
+        int fSharedMem;
+        FutexData* fFutex;
+        bool fPrivate;
+
+    protected:
+
+        void BuildName(const char* name, const char* server_name, char* res, int size);
+
+    public:
+
+        JackLinuxFutex():JackSynchro(), fSharedMem(-1), fFutex(NULL), fPrivate(false)
+        {}
+
+        bool Signal();
+        bool SignalAll();
+        bool Wait();
+        bool TimedWait(long usec);
+
+        bool Allocate(const char* name, const char* server_name, int value, bool internal = false);
+        bool Connect(const char* name, const char* server_name);
+        bool ConnectInput(const char* name, const char* server_name);
+        bool ConnectOutput(const char* name, const char* server_name);
+        bool Disconnect();
+        void Destroy();
+
+        void MakePrivate(bool priv);
+};
+
+} // end of namespace
+
+
+#endif
+

linux/JackPlatformPlug_os.h

@@ -54,8 +54,8 @@ namespace Jack { typedef JackPosixThread JackThread; }
 namespace Jack { typedef JackFifo JackSynchro; }
 */
 
-#include "JackPosixSemaphore.h"
-namespace Jack { typedef JackPosixSemaphore JackSynchro; }
+#include "JackLinuxFutex.h"
+namespace Jack { typedef JackLinuxFutex JackSynchro; }
 
 /* __JackPlatformChannelTransaction__ */
 /*