Memory leak with ocaml 3.09 but not with ocaml <= 3.08.1

Memory leak with ocaml 3.09 but not with ocaml <= 3.08.1

[Vincenzo Ciancia]

Hi all, I have a memory leak in ocamlfuse. Since fuse is based on callbacks,
and requests should be processed concurrently, I had to invert control, but
to avoid duplicate code in ocaml and c, I did things like this:

1. ocaml waits for messages from the kernel
2. then for each message received, ocaml creates an ocaml thread, and then   
calls C to allow processing of messages
3. after decoding a message (in an ocaml thread) C performs a callback to a
C callback for each operation, which in turn calls back ocaml

In this way I allow the fuse C library to decode messages, while I allow
ocaml to create threads for this purpose. 

Everything was working very well with ocaml 3.08, but using ocaml 3.09 I
have a memory leak as I said. 

My C callbacks, which then call back ocaml, look like this:

static int ops_OPNAME(ARGS)
{
  leave_blocking_section();
  value vstring;
  value vpath;
  value vres;
  value vtmp;
  int res=-1;
  vpath = copy_string(path);
  
  [OPERATION SPECIFIC CODE]

  if (Tag_val(vres)==1) /* Result is not Bad */
     { 
       [OPERATION SPECIFIC CODE]
     } 
  else 
  { 
    if (Is_block(Field(vres,0)))  /* This is EUNKNOWNERR of int in ocaml */ 
        res=-Int_val(Field(Field(vres,0),0));                           
    else res=-ml2c_unix_error(Int_val(Field(vres,0))); 
  } 
  enter_blocking_section(); 
  return res; 
}

If someone gives advice on how to discover where the memory leak is, I
promise to file a bug report if it is the case.

Bye

Vincenzo

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Re: [Caml-list] Memory leak with ocaml 3.09 but not with ocaml <= 3.08.1

[Florian Weimer]

* Vincenzo Ciancia:

> My C callbacks, which then call back ocaml, look like this:

>   leave_blocking_section();

>   vpath = copy_string(path);

I don't think it's allowed to invoke the Caml allocator while not
holding the run-time library lock.

Re: Memory leak with ocaml 3.09 but not with ocaml <= 3.08.1

[Vincenzo Ciancia]

Florian Weimer wrote:

>>   leave_blocking_section();
> 
>>   vpath = copy_string(path);
> 
> I don't think it's allowed to invoke the Caml allocator while not
> holding the run-time library lock.

That's why I hold the lock by calling "leave_blocking_section" at the
beginning of the function - it's "enter_blocking_section" that releases the
lock :)

I guess I will have to exclude pieces of code until the memory leak
disappears...

V.

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