Fix usb c displayport samsung gemini3#603
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…y redetection It appears that the crash in org_kde_powerdevil is related to several issues in libddcutil, including a potential Use-After-Free (UAF) in the display watch thread management, a lack of synchronization during display redetection, and a reachable assert(false) in the polling loop that could cause a crash in debug builds. The provided stack trace shows the main PowerDevil thread waiting to join a thread (likely the watch thread) that has crashed with a segmentation fault. The crash location suggests issues during thread termination and cleanup. Analysis of the Issues Use-After-Free in dw_main.c: In dw_stop_watch_displays(), the code accesses global_wdd->watch_mode and global_wdd->evdata before joining the thread. However, the thread function dw_watch_display_connections() (in dw_poll.c) calls dw_free_watch_displays_data(wdd) at the very end of its execution. If the thread finishes just as it's being stopped, global_wdd (which points to the same memory as wdd) may be freed while dw_stop_watch_displays() is still trying to access it. Missing Synchronization in dw_redetect_displays(): Display redetection discards all current display references. If callback threads are still running and accessing these references, a crash occurs. Furthermore, there is no guard against multiple concurrent redetection calls, which can happen during system resume when multiple display events are fired. Thread Termination Leaks and Logic Errors: In dw_recheck.c, queue entries are leaked when the thread terminates, and the wrong free function is used for thread data. In dw_poll.c, an assert(false) is present at the end of the thread function, which will cause a crash if the thread ever reaches that point (which it does upon termination). The following changes address these issues by fixing the UAF, adding a redetection mutex and callback thread synchronization, and cleaning up thread termination logic.
…msung monitor) (gemini3) aiprompt: Apr 09 08:12:17 jupiter org_kde_powerdevil[28197]: [116077] (i2c_check_open_bus_alive) Retrying i2c_check_edid_exists_by_dh() tryctr=1, dh=Display_Handle[i2c-9: fd=24]: Sleeping for 100 milliseconds Apr 09 08:12:17 jupiter org_kde_powerdevil[28197]: [116077] /dev/i2c-9, Checking EDID failed after 2 tries (B) Apr 09 08:12:17 jupiter org_kde_powerdevil[28197]: [116077] (check_supported_feature) busno=9, sleep-multiplier = 2.00. Testing for supported feature 0x10 returned Error_Info[DDCRC_DISCONNECTED in i2c_check_open_bus_alive]
aiprompt: Apr 09 08:12:17 jupiter org_kde_powerdevil[28197]: [116077] (i2c_check_open_bus_alive) Retrying i2c_check_edid_exists_by_dh() tryctr=1, dh=Display_Handle[i2c-9: fd=24]: Sleeping for 100 milliseconds Apr 09 08:12:17 jupiter org_kde_powerdevil[28197]: [116077] /dev/i2c-9, Checking EDID failed after 2 tries (B) Apr 09 08:12:17 jupiter org_kde_powerdevil[28197]: [116077] (check_supported_feature) busno=9, sleep-multiplier = 2.00. Testing for supported feature 0x10 returned Error_Info[DDCRC_DISCONNECTED in i2c_check_open_bus_alive]
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