Weston has only one output. Start a simple application like weston-simple-egl. Disconnected the connector. Weston will disable that output, then plug in back the connector. weston-simple-egl will not resume rendering being stuck

[4014018.805] wl_registry@3.global_remove(14)
[4014018.830] wl_registry@3.global(22, "wl_output", 3)
[4014018.948] wl_registry@2.global_remove(14)
[4014018.979] wl_registry@2.global(22, "wl_output", 3)
20 frames in 5 seconds: 4.000000 fps
[4014019.432]  -> wl_surface@9.set_opaque_region(nil)
[4014142.213] wl_display@1.delete_id(17)
[4014142.295] wl_callback@17.done(84567509)
[4014142.341]  -> wl_surface@9.frame(new id wl_callback@17)
[4014142.386]  -> wl_viv@10.enable_tile_status(wl_buffer@13, 1, 0, 1, 2147483648, 2147483648)
[4014142.500]  -> wl_surface@9.attach(wl_buffer@13, 0, 0)
[4014142.558]  -> wl_surface@9.damage(61, 62, 127, 127)
[4014142.612]  -> wl_surface@9.commit()
[4014142.644] wl_buffer@18.release()
[4014143.012]  -> wl_surface@9.set_opaque_region(nil)
[4014161.056] wl_display@1.delete_id(17)
[4014161.138] wl_callback@17.done(84567589)
[4014161.184]  -> wl_surface@9.frame(new id wl_callback@17)
[4014161.230]  -> wl_viv@10.enable_tile_status(wl_buffer@18, 1, 0, 1, 2147483648, 2147483648)
[4014161.330]  -> wl_surface@9.attach(wl_buffer@18, 0, 0)
[4014161.386]  -> wl_surface@9.damage(61, 62, 127, 127)
[4014161.449]  -> wl_surface@9.commit()
[4014161.485] wl_buffer@19.release()
[4014161.802]  -> wl_surface@9.set_opaque_region(nil)

Forcibly closing weston-simple-egl gives: malloc(): smallbin double linked list corrupted. This seems to originate in libdrm in drmModeAtomicCommit(). Hopefully other can replicate this as I don't have a cross-compiled Valgrind.

__GI_raise (sig=sig@entry=6)
    at /usr/src/debug/glibc/2.27-r0/git/sysdeps/unix/sysv/linux/raise.c:51
#1  0x0000ffffb62df1d0 in __GI_abort () at /usr/src/debug/glibc/2.27-r0/git/stdlib/abort.c:79
#2  0x0000ffffb63177b0 in __libc_message (action=action@entry=do_abort, 
    fmt=fmt@entry=0xffffb63d4d10 "%s\n")
    at /usr/src/debug/glibc/2.27-r0/git/sysdeps/posix/libc_fatal.c:181
#3  0x0000ffffb631da9c in malloc_printerr (
    str=str@entry=0xffffb63d0d90 "malloc(): smallbin double linked list corrupted")
    at /usr/src/debug/glibc/2.27-r0/git/malloc/malloc.c:5350
#4  0x0000ffffb6320f10 in _int_malloc (av=av@entry=0xffffb63faa70 <main_arena>, 
    bytes=bytes@entry=52) at /usr/src/debug/glibc/2.27-r0/git/malloc/malloc.c:3648
#5  0x0000ffffb6323050 in __libc_calloc (n=<optimized out>, elem_size=<optimized out>)
    at /usr/src/debug/glibc/2.27-r0/git/malloc/malloc.c:3436
#6  0x0000ffffb5f4b490 in drmModeAtomicCommit () from /usr/lib/libdrm.so.2
#7  0x0000ffffb6056fa0 in drm_pending_state_apply_atomic (pending_state=0x3f132280, 
    mode=DRM_STATE_APPLY_ASYNC) at libweston/compositor-drm.c:2694
#8  0x0000ffffb6057110 in drm_pending_state_apply (pending_state=0x3f132280)
    at libweston/compositor-drm.c:2773
#9  0x0000ffffb6057b08 in drm_repaint_flush (compositor=0x3ed47830, repaint_data=0x3f132280)
    at libweston/compositor-drm.c:3076
#10 0x0000ffffb649e794 in output_repaint_timer_handler (data=0x3ed47830)
    at libweston/compositor.c:2551
#11 0x0000ffffb64597e4 in ?? () from /usr/lib/libwayland-server.so.0
#12 0x00000000ffffffff in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

PS: Not sure if there are two issues here: that the application doesn't resume rendering and the fact that it crashes this way when trying to close it forcibly.