Hi, Actually I've looked into this further in the meantime and it seems that the actual cause of the problem is elsewhere. It seems to be a basic problem of how modules are made to depend on libs. For example, avpops and lcr both depend on kcore. Their makefiles specify this through: SER_LIBS+=$(SERLIBPATH)/kcore/kcore which Makefile.rules (line 164) translates into SER_LIBS_DEPS=$(SERLIBPATH)/kcore/libkcore.so which in turn gets the following rule and recipe a few lines below: $(SER_LIBS_DEPS): FORCE @$(MAKE) -wC $(dir $@) .......... So what happens during a parallel build is this: Make's thread A starts compiling avpops while make's thread B starts compiling lcr at the same time. Both make threads see the dependency on libkcore.so and thus execute the sub-make to build it. Which means that you now have two make children running at the same time in the same directory, trying to compile the same target. Obviously they get into each others way. I'm not sure if the make children are supposed to communicate with each other and if one is supposed to know that the other one is compiling kcore already or not. Taking out the FORCE dependency seems to help a little, but it's still ending up with multiple makes trying to build the same targets. I'm still playing this this, trying to figure out if there's some make flags that will fix it or if it's maybe a fundamental problem of make and/or the way the makefiles are made. cheers On 01/30/13 07:15, Daniel-Constantin Mierla wrote: