# This patch introduce --enable-iopriority to define HAVE_IOPRIORITY
# The default is determined checking if SYS_ioprio_get is available or not
# https://bugs.gentoo.org/show_bug.cgi?id=442622
--- a/Process.c
+++ b/Process.c
@@ -517,6 +517,7 @@ static void Process_writeField(Process* this, RichString* str, ProcessField fiel
    #ifdef HAVE_CGROUP
    case CGROUP: snprintf(buffer, n, "%-10s ", this->cgroup); break;
    #endif
+   #ifdef HAVE_IOPRIORITY
    case IO_PRIORITY: {
       int klass = IOPriority_class(this->ioPriority);
       if (klass == IOPRIO_CLASS_NONE) {
@@ -535,6 +536,7 @@ static void Process_writeField(Process* this, RichString* str, ProcessField fiel
       }
       break;
    }
+   #endif
    default:
       snprintf(buffer, n, "- ");
    }
@@ -603,6 +605,7 @@ bool Process_changePriorityBy(Process* this, size_t delta) {
    return Process_setPriority(this, this->nice + delta);
 }
 
+#ifdef HAVE_IOPRIORITY
 IOPriority Process_updateIOPriority(Process* this) {
    IOPriority ioprio = syscall(SYS_ioprio_get, IOPRIO_WHO_PROCESS, this->pid);
    this->ioPriority = ioprio;
@@ -613,6 +616,7 @@ bool Process_setIOPriority(Process* this, IOPriority ioprio) {
    syscall(SYS_ioprio_set, IOPRIO_WHO_PROCESS, this->pid, ioprio);
    return (Process_updateIOPriority(this) == ioprio);
 }
+#endif
 
 /*
 [1] Note that before kernel 2.6.26 a process that has not asked for
@@ -781,8 +785,10 @@ int Process_compare(const void* v1, const void* v2) {
    case CGROUP:
       return strcmp(p1->cgroup ? p1->cgroup : "", p2->cgroup ? p2->cgroup : "");
    #endif
+   #ifdef HAVE_IOPRIORITY
    case IO_PRIORITY:
       return Process_effectiveIOPriority(p1) - Process_effectiveIOPriority(p2);
+   #endif
    default:
       return (p1->pid - p2->pid);
    }
--- a/ProcessList.c
+++ b/ProcessList.c
@@ -685,7 +685,9 @@ static bool ProcessList_processEntries(ProcessList* this, const char* dirname, P
       unsigned long long int lasttimes = (process->utime + process->stime);
       if (! ProcessList_readStatFile(process, dirname, name, command))
          goto errorReadingProcess;
+      #ifdef HAVE_IOPRIORITY
       Process_updateIOPriority(process);
+      #endif
       float percent_cpu = (process->utime + process->stime - lasttimes) / period * 100.0;
       process->percent_cpu = MAX(MIN(percent_cpu, cpus*100.0), 0.0);
       if (isnan(process->percent_cpu)) process->percent_cpu = 0.0;
--- a/configure.ac
+++ b/configure.ac
@@ -71,6 +71,12 @@ if test "x$enable_cgroup" = xyes; then
    AC_DEFINE(HAVE_CGROUP, 1, [Define if cgroup support enabled.])
 fi
 
+AC_ARG_ENABLE(iopriority, [AC_HELP_STRING([--enable-iopriority], [enable IO priority support])], ,
+   AC_CHECK_DECLS(SYS_ioprio_get, [enable_iopriority=yes], [enable_iopriority=no], [#include <sys/syscall.h>]))
+if test "x$enable_iopriority" = xyes; then
+   AC_DEFINE(HAVE_IOPRIORITY, 1, [Define if IO priority support enabled.])
+fi
+
 AC_ARG_ENABLE(vserver, [AC_HELP_STRING([--enable-vserver], [enable VServer support])], ,enable_vserver="no")
 if test "x$enable_vserver" = xyes; then
     AC_DEFINE(HAVE_VSERVER, 1, [Define if vserver support enabled.])
--- a/htop.c
+++ b/htop.c
@@ -851,6 +851,7 @@ int main(int argc, char** argv) {
          refreshTimeout = 0;
          break;
       }
+#ifdef HAVE_IOPRIORITY
       case 'i':
       {
          Process* p = (Process*) Panel_getSelected(panel);
@@ -870,6 +871,7 @@ int main(int argc, char** argv) {
          refreshTimeout = 0;
          break;
       }
+#endif
       case 'I':
       {
          refreshTimeout = 0;