[Mesa-dev] [Bug 106572] Simply linking against libOpenCL.so tries accessing the GPU

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106572

            Bug ID: 106572
           Summary: Simply linking against libOpenCL.so tries accessing
                    the GPU
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Mesa core
          Assignee: mesa-dev at lists.freedesktop.org
          Reporter: bugs.freedesktop at haasn.xyz
        QA Contact: mesa-dev at lists.freedesktop.org

$ echo 'int main() {}' > test.c && gcc -o test test.c -lOpenCL && strace -e
open ./test
open("/dev/dri", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 4
open("/dev/dri", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 4
open("/dev/dri", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 4
open("/dev/dri", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 4
open("/sys/dev/char/226:128/device/drm",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 4
open("/sys/dev/char/226:128/device/drm",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 5
open("/dev/dri", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 5
open("/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 5
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 5
open("/sys/devices/system/cpu/online", O_RDONLY|O_CLOEXEC) = 5
open("/sys/dev/char/226:128/device/drm",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 5
open("/sys/dev/char/226:128/device/drm",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 5
open("/sys/dev/char/226:128/device/drm",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 5
+++ exited with 0 +++

This behavior surprises me because e.g. libGL.so does not have the same sort of
behavior, and neither do libvulkan.so or other third party implementations of
OpenGL/OpenCL.

Merely *linking* to a library should not cause any runtime GPU access. Normally
I'd expect this kind of loading logic to happen when the CL device itself is
initialized, similar to how OpenGL's GPU-specific drivers only get initialized
when calling `glXCreateContext` and ditto for vkCreateInstance /
vkCreateDevice.

Context: https://bugs.gentoo.org/show_bug.cgi?id=656086

Since this behavior surprises me, I'm also filing a bug here, even though the
issue is technically downstream. Maybe we could get some elaboration.

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