[Bug 102179] clEnqueueReadBuffer VM_PAGE FAULT

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Sat Aug 12 14:40:54 UTC 2017


https://bugs.freedesktop.org/show_bug.cgi?id=102179

Janpieter Sollie <janpieter.sollie at dommel.be> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |major

--- Comment #3 from Janpieter Sollie <janpieter.sollie at dommel.be> ---
interesting note:
the following code allows me to execute the clEnqueueReadBuffer:
//set kernel arguments, limited to 1
    clSetKernelArg ( devdb[nr_of_devices].kernel, 0,
sizeof(devdb[nr_of_devices].output), &devdb[nr_of_devices].output);

//run kernel
clEnqueueNDRangeKernel(..)
//read buffer
clEnqueueReadBuffer (((device*)device_obj)->command_queue,
((device*)device_obj)->output, CL_FALSE, 0, 16,
((device*)device_obj)->host_output, 0, NULL, NULL);

while it does not work with any 2nd, 3rd, ... kernel parameter, eg:
clSetKernelArg ( devdb[nr_of_devices].kernel, 0,
sizeof(devdb[nr_of_devices].output), &devdb[nr_of_devices].output);
clSetKernelArg ( devdb[nr_of_devices].kernel, 1,
sizeof(devdb[nr_of_devices].output2), &devdb[nr_of_devices].output2);

hangs at reading output. but no warning of VM_PAGE_FAULTS, these occur when
output is the last argument

because I think this is a blocker for most OpenCL users to get their data back,
I'm increasing it to major (also, this cannot be analyzed easily: every time
the call hangs, I have to reboot my pc, as the process becomes a zombie)

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