Priority changes are applied to childprocesses as well

Changes to the priority of a unixprocess does apply the priority
also to all childprocesses and threads.

Change-Id: Iaff1a5f7ef0742268d527e6b6800bbd47c39146c
Reviewed-by: Lasse Holmstedt <lasse.holmstedt@nokia.com>
Reviewed-by: Chris Craig <ext-chris.craig@nokia.com>

3 files changed, 26 insertions, 13 deletions

diff --git a/src/core/procutils.cpp b/src/core/procutils.cpp
index 8c98d56..7ecfd28 100644
--- a/src/core/procutils.cpp
+++ b/src/core/procutils.cpp
@@ -45,6 +45,7 @@
 #include <sys/socket.h>
 #include <sys/resource.h>
 #include <signal.h>
+#include <errno.h>
 
 #include <QFile>
 #include <QFileInfo>
@@ -55,7 +56,6 @@
 #include <QRegExp>
 #elif defined(Q_OS_MAC)
 #include <sys/sysctl.h>
-#include <errno.h>
 #endif
 
 
@@ -409,6 +409,22 @@ void ProcUtils::sendSignalToProcess(pid_t pid, int sig)
     ::kill(pid, sig);
 }
 
+/*!
+  Set a process or process group priority
+ */
+
+void ProcUtils::setPriority(pid_t pid, qint32 priority)
+{
+    pid_t pgrp = ::getpgid(pid);
+    if (pgrp != -1 && pgrp != ::getpgrp()) {
+        if (::setpriority(PRIO_PGRP, pgrp, priority) == 0)
+            return;
+        qErrnoWarning(errno, "Failed to set process group %d priority to %d", pgrp, priority);
+    }
+    if (::setpriority(PRIO_PROCESS, pid, priority))
+        qErrnoWarning(errno, "Failed to set process %d priority to %d", pid, priority);
+}
+
 #include "moc_procutils.cpp"
 
 QT_END_NAMESPACE_PROCESSMANAGER
diff --git a/src/core/procutils.h b/src/core/procutils.h
index 3119d08..68008e7 100644
--- a/src/core/procutils.h
+++ b/src/core/procutils.h
@@ -111,6 +111,7 @@ public:
     static bool   setOomAdjustment(pid_t pid, qint32 oomAdjustment);
 
     static void   sendSignalToProcess(pid_t pid, int sig);
+    static void   setPriority(pid_t pid, qint32 priority);
 };
 
 QT_END_NAMESPACE_PROCESSMANAGER
diff --git a/src/core/unixprocessbackend.cpp b/src/core/unixprocessbackend.cpp
index 76bd063..18e8123 100644
--- a/src/core/unixprocessbackend.cpp
+++ b/src/core/unixprocessbackend.cpp
@@ -44,7 +44,6 @@
 #include <errno.h>
 #include <signal.h>
 #include <QDebug>
-#include <QFile>
 
 QT_BEGIN_NAMESPACE_PROCESSMANAGER
 
@@ -101,18 +100,16 @@ qint32 UnixProcessBackend::actualPriority() const
 }
 
 /*!
-    Set the process priority to \a priority
+    Set the process priority to \a priority.  If the process
+    is in its own process group, we fix the process priority
+    of the entire group.
 */
 
 void UnixProcessBackend::setDesiredPriority(qint32 priority)
 {
     ProcessBackend::setDesiredPriority(priority);
-    if (m_process) {
-        // ### Is this always correct?  Could we have an m_process without a pid?
-        if (setpriority(PRIO_PROCESS, m_process->pid(), priority))
-            qWarning() << "Failed to set process priority from " << actualPriority() <<
-                          "to" << priority << " : errno = " << errno;
-    }
+    if (m_process)
+        ProcUtils::setPriority(m_process->pid(), priority);
 }
 
 #if defined(Q_OS_LINUX)
@@ -249,10 +246,9 @@ qint64 UnixProcessBackend::write(const char *data, qint64 maxSize)
 */
 void UnixProcessBackend::handleProcessStarted()
 {
-    if (m_info.contains(ProcessInfoConstants::Priority) &&
-        setpriority(PRIO_PROCESS, m_process->pid(), m_info.priority()))
-        qWarning() << "Failed to set process priority at startup from " << actualPriority() <<
-            "to" << m_info.priority()  << " : errno = " << errno;
+    if (m_info.contains(ProcessInfoConstants::Priority))
+        ProcUtils::setPriority(m_process->pid(), m_info.priority());
+
     if (m_info.contains(ProcessInfoConstants::OomAdjustment) &&
         !ProcUtils::setOomAdjustment(m_process->pid(), m_info.oomAdjustment()))
         qWarning() << "Failed to set process oom score at startup from " << actualOomAdjustment() <<