Resume device output after user program restart #23
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kxo has a critical issue: if the userspace program xo-user exits while the game is paused, restarting the program will cause it to hang. The userspace program communicates the game state to the kernel module via the 'kxo_state' attribute exposed through sysfs. This attribute reflects the current game state (e.g., paused, quitting) and controls whether the kernel module continues to produce output. However, if the userspace program exits while the game is paused, the 'display' flag is not cleared. As a result, the kernel module does not resume producing output when the program is relaunched, even though it is still functioning correctly. This patch resolves the issue by resetting the 'display' flag when the userspace program exits.
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If this change is applied, when running xo-user in multiple user space programs, pausing and exiting in one program will cause the others to resume from pause. I’m not sure if that’s the intended behavior. My suggestion is to move attr_obj.display = 49; inside the if statement. if (atomic_dec_and_test(&open_cnt)) {
del_timer_sync(&timer);
flush_workqueue(kxo_workqueue);
fast_buf_clear();
+ attr_obj.display = 49;
}This would keep the current behavior, where other programs fail to properly resume after being paused, but since your commit message only mentions ensuring that restart works correctly, I think it’s better to minimize unintended side effects. As for the multiple–user space program issue, I think it can be discussed separately. |
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If the userspace program exits while the game is paused, the
displayflag is not cleared, causing the kernel module to stop producing output. As a result, restarting the program in this state causes it to hang on waiting for device data.This patch resets the
displayflag on program exit, ensuring the kernel module resumes output normally when the program is restarted.