Re: problem with bupc_extern_free

From: Dan Bonachea (bonachea_at_cs_dot_berkeley_dot_edu)
Date: Thu Oct 20 2005 - 00:54:25 PDT

  • Next message: Christian Terboven: "AW: problem with bupc_extern_free"
    Hi Christian - thanks for writing..
    
    We see two bugs in your attached code (tracked down by our developer Paul 
    Hargrove), both of which are probably triggered by poor documentation on our 
    part in bupc_extern.h.
    
    1) bupc_extern_free() has essentially the same semantics as upc_free(), and as 
    such should only be called by a single thread per allocation. Ie, in UPC, all 
    threads collectively call upc_all_alloc, but only one may call the 
    (non-collective) upc_free.  This is one probable cause of the crash.
    
    2) In the .upc file the code calls bupc_local_to_shared, but ignores the 
    return value which provides the restored pointer-to-shared. This leads to an 
    overrun (because it uses the local pointer rather than the shared pointer) of 
    allocated memory, which is the second probable cause for the crash upon free.
    
    We've improved our documentation comments in bupc_extern.h, and a new version 
    is attached for your convenience.
    
    Thanks for your patience...
    Dan
    
    
    At 03:51 PM 10/19/2005, Christian Terboven wrote:
    >Hi all.
    >
    >I got a SIGSEV when calling bupc_extern_free:
    >
    >=> upcrun -n 1 test01.exe
    >UPCR: UPC thread 0 of 1 on linuxoc01.rz.RWTH-Aachen.DE (process 0 of 1, 
    >pid=29966)
    >I would like to be alone ...
    >I am 0 out of 1 ...
    >I am alone again ...
    >
    >=> upcrun -n 2 test01.exe
    >UPCR: UPC threads 0..1 of 2 on linuxoc01.rz.RWTH-Aachen.DE (process 0 of 1, 
    >pid=29974)
    >I would like to be alone ...
    >I am 0 out of 2 ...
    >I am 1 out of 2 ...
    >I am alone again ...
    >*** Caught a fatal signal: SIGSEGV(11) on node 0/1
    >zsh: segmentation fault (core dumped)  upcrun -n 2 test01.exe
    >
    >I am using Berkeley-UPC 2.2.0 on an Opteron Linux 2.6.12#smp (Fedora Core 3).
    >I attached a reduced version of my code  is this a problem in there or what?
    >
    >
    >
    >Regards,
    >Christian
    >
    >
    
    
    


  • Next message: Christian Terboven: "AW: problem with bupc_extern_free"