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Old 06-25-04, 03:55 PM   #1
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Join Date: Jun 2004
Posts: 1
Question Hung system after shmat()


I have an interesting situation whereby I can create a hung system state when using shared memory and the GLX driver in combination. The system completely freezes and I need to press the "Reset" button ( Oh my god, when did I do that last. I am use to 100day uptimes).

Here is what I did:

I am trying to map the virtual frame buffer of Xvfb to a texture. Using mmap file reads into a local memory buffer, this works well. To speed things up and avoid the double copying, I was trying to copy shared memory directly to texture memory.

The system hang occurs at the time the OpenGL (glut) window is opened. Here is the code:

int main (int argc, char *argv[])
int shmid=557073; // shmid number is the output from 'Xvfb -shmem'

fprintf (stderr,"testprogram\n\n");

shmbuffer = shmat(shmid, (void *)0, 0);
if (shmbuffer == (void *)-1) {
fprintf (stderr,"shmbuffer attached ...\n");

glutInitWindowPosition(0, 0);
glutInitWindowSize(XWIDTH, XHEIGHT);
glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
if (glutCreateWindow("test") <= 0) {
fprintf (stderr,"New window created ...\n");

// Hang occurs about here here, i.e. the following is ...

/* Clear texture buffer */
fprintf (stderr,"Texture buffer cleared ...\n");
// ... never printed

System: Mandrake10
nvidia: 1.0-5336
kernel: 2.6.3-7mdk and 2.6.7
Xfree: 4.4.0

I didn't test this with any other shared memory segment yet as the Xvfb code looks straight-and-plain. I also did not test kernel 2.4 as I don't have that installed right now.

Maybe others can confirm this hang ... Maybe someone at nvidia can run a debug version of the driver to see if this a driver problem or a kernel issue.
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