Add nice/ioprio to MythSystem

Allows a MythSystem user to specify nice and io priority values that a
task should run at.  These will be set after the fork, so they will not
disrupt instances of a shared thread that would otherwise not allow the
current mechanism of niceing the thread prior to running MythSystem.

Author: wagnerrp

mythtv/libs/libmythbase/mythsystem.cpp

@@ -36,6 +36,8 @@
 
 void MythSystem::initializePrivate(void)
 {
+    m_nice = 0;
+    m_ioprio = 0;
 #if CONFIG_CYGWIN || defined(_WIN32)
     d = new MythSystemWindows(this);
 #else
@@ -131,6 +133,24 @@ void MythSystem::SetDirectory(const QString &directory)
     m_directory = QString(directory);
 }
 
+bool MythSystem::SetNice(int nice)
+{
+    if( !d || (GetStatus() != GENERIC_EXIT_START) )
+        return false;
+
+    m_nice = nice;
+    return true;
+}
+
+bool MythSystem::SetIOPrio(int prio)
+{
+    if( !d || (GetStatus() != GENERIC_EXIT_START) )
+        return false;
+
+    m_ioprio = prio;
+    return true;
+}
+
 /** \fn MythSystem::Run()
  *  \brief Runs a command inside the /bin/sh shell. Returns immediately
  */

mythtv/libs/libmythbase/mythsystem.h

@@ -50,6 +50,8 @@ class MBASE_PUBLIC MythSystem : public QObject
         void SetCommand(const QString &, uint);
         void SetCommand(const QString &, const QStringList &, uint);
         void SetDirectory(const QString &);
+        bool SetNice(int nice);
+        bool SetIOPrio(int prio);
 
         void Run(time_t timeout = 0);
         uint Wait(time_t timeout = 0);
@@ -91,6 +93,9 @@ class MBASE_PUBLIC MythSystem : public QObject
         QStringList &GetArgs()       { return m_args; };
         void SetArgs(QStringList &args)  { m_args = args; };
 
+        int GetNice()                { return m_nice; };
+        int GetIOPrio()              { return m_ioprio; };
+
         QBuffer *GetBuffer(int index) { return &m_stdbuff[index]; };
 
         void Unlock() { m_semReady.release(1); };
@@ -118,6 +123,9 @@ class MBASE_PUBLIC MythSystem : public QObject
         QStringList m_args;
         QString     m_directory;
 
+        int         m_nice;
+        int         m_ioprio;
+
         Setting_t   m_settings;
         QBuffer     m_stdbuff[3];
 };

mythtv/libs/libmythbase/mythversion.h

@@ -12,7 +12,7 @@
 /// Update this whenever the plug-in API changes.
 /// Including changes in the libmythbase, libmyth, libmythtv, libmythav* and
 /// libmythui class methods used by plug-ins.
-#define MYTH_BINARY_VERSION "0.25.20110910-2"
+#define MYTH_BINARY_VERSION "0.25.20110920-1"
 
 /** \brief Increment this whenever the MythTV network protocol changes.
  *

mythtv/libs/libmythbase/system-unix.cpp

@@ -2,6 +2,7 @@
 // Own header
 #include "mythsystem.h"
 #include "system-unix.h"
+#include "util.h"
 
 // compat header
 #include "compat.h"
@@ -676,6 +677,9 @@ void MythSystemUnix::Fork(time_t timeout)
     // check before fork to avoid QString use in child
     bool setpgidsetting = GetSetting("SetPGID");
 
+    int niceval = m_parent->GetNice();
+    int ioprioval = m_parent->GetIOPrio();
+
     /* Do this before forking in case the child miserably fails */
     m_timeout = timeout;
     if( timeout )
@@ -801,6 +805,12 @@ void MythSystemUnix::Fork(time_t timeout)
                  << strerror(errno) << endl;
         }
 
+        /* Set nice and ioprio values if non-default */
+        if (niceval)
+            myth_nice(niceval);
+        if (ioprioval)
+            myth_ioprio(ioprioval);
+
         /* run command */
         if( execv(command, cmdargs) < 0 )
         {