... and given getpid(2) implementation, a pid based table could be quite expensive, since MyStruct is accessed very very often.
2015-09-05 16:03 GMT+02:00 Giacomo Tesio <giac...@tesio.it>: > 2011-05-20 3:30 GMT+02:00 erik quanstrom <quans...@quanstro.net>: > >> one note is that while i'm aware of privalloc(2), i didn't use it. the >> implementation doesn't appear correct for shared-memory procs. >> i think there are two issues >> - locking is unnecessary. the only preemptable unit of execution is >> a process and each process is guarenteed to have its own instance >> of _privates and _nprivates. >> - for shared-memory procs, we will run out of privates because >> the static privinit will be falsely shared. privinit should be replaced >> by using a private entry. >> > > In a set of processes that share memory, I need a single per-process > location to store the address of structure (which is in turn allocated in > the global memory space). > > Privalloc(2) seemed what I need, but seem that I can't use it properly. > > In the parent process I do: > > 1) initialialize a global variable p = (MyStruct **)privalloc(); > 2) allocate a MyStruct for every process I'm going to spawn > 3) spawn processes with rfork(RFMEM|RFPROC) > > The spawn() function that call rfork takes a MyStruct* as argument and > assign it to *p in the new process. > For extra safety I added an assert(*p == nil) just after rfork, and after > a few (apparently?) successful spawns, the assert fails. > > What I need is a sort of thread-local storage for the MyStruct*, so that > each child process can find it's own dedicated MyStruct. > I know that could get this with an hashtable based on the pid, but I'd > prefer to avoid the book keeping if possible. > > > Giacomo >
