diff --git a/kernel/ps4_pthread.pas b/kernel/ps4_pthread.pas
index a42e14d3..f45b9a41 100644
--- a/kernel/ps4_pthread.pas
+++ b/kernel/ps4_pthread.pas
@@ -319,13 +319,13 @@ begin
    Exit(EAGAIN);
   end;
 
-  _sig_lock;
    if (data^.Attr.cpuset<>0) then
    begin
+    _sig_lock;
      SetThreadAffinityMask(Handle,attr^.cpuset);
+    _sig_unlock;
    end;
    sys_set_thread_prior(Handle,data^.Attr.prio);
-  _sig_unlock;
 
  end;
 
@@ -577,16 +577,18 @@ function ps4_pthread_setprio(_pthread:pthread;prio:Integer):Integer; SysV_ABI_CD
 begin
  if (_pthread=nil) then Exit(EINVAL);
 
- if (prio>767) then Exit(EINVAL);
- if (prio<256) then Exit(EINVAL);
+ if (_pthread^.Attr.sched_policy=SCHED_OTHER) or
+    (_pthread^.Attr.prio=prio) then
+ begin
+  _pthread^.Attr.prio:=prio;
+  Exit(0);
+ end;
 
- _sig_lock;
-  Result:=sys_set_thread_prior(_pthread^.handle,prio);
-  if (Result<>0) then
-  begin
-   _pthread^.Attr.prio:=prio;
-  end;
- _sig_unlock;
+ Result:=sys_set_thread_prior(_pthread^.handle,prio);
+ if (Result<>0) then
+ begin
+  _pthread^.Attr.prio:=prio;
+ end;
 end;
 
 function ps4_scePthreadSetprio(_pthread:pthread;prio:Integer):Integer; SysV_ABI_CDecl;
@@ -612,11 +614,19 @@ function ps4_pthread_setschedparam(_pthread:pthread;policy:Integer;param:PSceKer
 begin
  if (_pthread=nil) or (param=nil) then Exit(EINVAL);
 
- Result:=ps4_pthread_setprio(_pthread,param^.sched_priority);
- if (Result<>0) then Exit;
+ if (_pthread^.Attr.sched_policy=policy) and
+    ((policy=SCHED_OTHER) or (_pthread^.Attr.prio=param^.sched_priority)) then
+ begin
+  _pthread^.Attr.prio:=param^.sched_priority;
+  Exit(0);
+ end;
 
- _pthread^.Attr.sched_policy:=policy;
- Result:=0;
+ Result:=sys_set_thread_prior(_pthread^.handle,param^.sched_priority);
+ if (Result<>0) then
+ begin
+  _pthread^.Attr.sched_policy:=policy;
+  _pthread^.Attr.prio:=param^.sched_priority;
+ end;
 end;
 
 function ps4_scePthreadSetschedparam(_pthread:pthread;policy:Integer;param:PSceKernelSchedParam):Integer; SysV_ABI_CDecl;
diff --git a/sys/sys_pthread.pas b/sys/sys_pthread.pas
index 42e2d25c..4942d348 100644
--- a/sys/sys_pthread.pas
+++ b/sys/sys_pthread.pas
@@ -252,7 +252,9 @@ end;
 
 function sys_get_thread_prior(handle:TThreadID):Integer;
 begin
- Result:=System.ThreadGetPriority(handle);
+ _sig_lock;
+  Result:=System.ThreadGetPriority(handle);
+ _sig_unlock;
  Result:=767-(((Result+15)*511) div 30);
 end;
 
@@ -293,15 +295,18 @@ const
 
 function sys_set_thread_prior(handle:TThreadID;prio:Integer):Integer;
 begin
+ if (prio>767) or (prio<256) then Exit(EINVAL);
  prio:=(((767-prio)*30) div 511);
  prio:=PRIORITY_TABLE[prio];
- if System.ThreadSetPriority(handle,prio) then
- begin
-  Result:=0;
- end else
- begin
-  Result:=ESRCH;
- end;
+ _sig_lock;
+  if System.ThreadSetPriority(handle,prio) then
+  begin
+   Result:=0;
+  end else
+  begin
+   Result:=ESRCH;
+  end;
+ _sig_unlock;
 end;