[osg-users] [patch] PThread.c++ creation error, lower stack size limit

[Robert Osfield]

Thanks David, changes look sound, now merged and submitted to svn/trunk.

On Fri, Oct 16, 2009 at 1:31 PM, David Fries <david at fries.net> wrote:
> This was against 2.8.1, but I see the trunk is identical.
> Any issues with using PTHREAD_STACK_MIN?
> http://www.opengroup.org/onlinepubs/9699919799/functions/pthread_attr_getstacksize.html
>
>
> I was trying to create a lot of threads under 32 bit Linux, but could
> only create 376, then the program would hang.
> 376 * 8MB stack per thread = 3008 MB
> The stack size allocated per thread blew the process address stack.
> To get more threads you have to specify a smaller per thread stack,
> but while the Thread::start says it will limit the stack size to the
> smallest allowable stack size, it won't let it be smaller than the
> default.  I included the limits.h header to use PTHREAD_STACK_MIN as
> the minimum stack size.
>
> As for the deadlock, if the pthread_create failed, the new thread
> doesn't exist and doesn't call threadStartedBlock.release(), so the
> existing thread deadlocks on threadStartedBlock.block().  Only block
> if the thread was started.
>
> --
> David Fries <david at fries.net>
> http://fries.net/~david/ (PGP encryption key available)
>
>
> Index: src/OpenThreads/pthreads/PThread.c++
> ===================================================================
> --- src/OpenThreads/pthreads/PThread.c++        (revision 10273)
> +++ src/OpenThreads/pthreads/PThread.c++        (working copy)
> @@ -21,6 +21,7 @@
>  #include <sys/types.h>
>  #include <unistd.h>
>  #include <pthread.h>
> +#include <limits.h>
>
>  #if defined __linux || defined __sun || defined __APPLE__
>  #include <string.h>
> @@ -588,30 +589,29 @@
>
>     PThreadPrivateData *pd = static_cast<PThreadPrivateData *> (_prvData);
>
> -    size_t defaultStackSize;
> -    pthread_attr_getstacksize( &thread_attr, &defaultStackSize);
> -    if(status != 0) {
> -       return status;
> +    //-------------------------------------------------------------------------
> +    // Set the stack size if requested, but not less than a platform reasonable
> +    // value.
> +    //
> +    if(pd->stackSize) {
> +        if(pd->stackSize < PTHREAD_STACK_MIN)
> +            pd->stackSize = PTHREAD_STACK_MIN;
> +        pthread_attr_setstacksize( &thread_attr, pd->stackSize);
> +        if(status != 0) {
> +            return status;
> +        }
>     }
>
> -    if(defaultStackSize < pd->stackSize) {
> -
> -       pthread_attr_setstacksize( &thread_attr, pd->stackSize);
> -       if(status != 0) {
> -           return status;
> -       }
> -    }
> -
>     //-------------------------------------------------------------------------
>     // Now get what we actually have...
>     //
> -    pthread_attr_getstacksize( &thread_attr, &defaultStackSize);
> +    size_t size;
> +    pthread_attr_getstacksize( &thread_attr, &size);
>     if(status != 0) {
>        return status;
>     }
> +    pd->stackSize = size;
>
> -    pd->stackSize = defaultStackSize;
> -
>     //-------------------------------------------------------------------------
>     // Prohibit the stack size from being changed.
>     //
> @@ -635,18 +635,15 @@
>     status = pthread_create(&(pd->tid), &thread_attr,
>                            ThreadPrivateActions::StartThread,
>                            static_cast<void *>(this));
> -
> -    // wait till the thread has actually started.
> -    pd->threadStartedBlock.block();
>
> -    if(status != 0) {
> -       return status;
> +    if(status == 0) {
> +        // wait till the thread has actually started.
> +        pd->threadStartedBlock.block();
> +
> +        pd->idSet = true;
>     }
>
> -    pd->idSet = true;
> -
> -    return 0;
> -
> +    return status;
>  }
>
>  //-----------------------------------------------------------------------------
>
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