When debugging in kernel space, I sometimes wish to search for thread according to its backtrace frames among a group of threads, like all the threads on a specific task.
For example, getting kernel_task id
(lldb) showalltasks
task vm_map ...command
0xffffff800d828550 0xffffff800a1038d8 ...kernel_task
Dumping all threads belonged to kernel_task
(lldb) showtaskthreads 0xffffff800d828550
task vm_map ipc_space #acts flags pid process io_policy wq_state command
0xffffff800d828550 0xffffff800a1038d8 0xffffff800d5d17c0 140 0 0xffffff8007abb460 -1 -1 -1 kernel_task
thread thread_id processor base pri sched_mode io_policy state ast waitq wait_event wmesg thread_name
0xffffff8007acf098 0x65 0xffffff8007a8a7b8 92 92 fixed bound WU L 0xffffff804119e550 0xffffff8007a87a30 <vm_page_free_wanted>
0xffffff800d83f4c0 0x66 0xffffff8007a8a7b8 0 0 fixed bound RI L
0xffffff800d83f958 0x67 0xffffff8041ad6000 95 95 fixed WU L 0xffffff804119c240 0xffffff8007303840 <sched_timeshare_maintenance_continue> sched_maintenance_thread
0xffffff800d83fdf0 0x68 0xffffff8041ad6000 80 80 fixed WU L 0xffffff804119e850 0xffffff8007acf9f0
0xffffff800d83f028 0x69 0xffffff8007a8a7b8 93 93 fixed WU 0xffffff804119e5e0 0xffffff8007acfa08
Now I can see thread id's and lots of other information about the threads, but how can I observe the threads' backtrace ?
For whatever reason, the xnu kernel debugging macros use both "thread" and "activation" (abbreviated "act") terminology when talking about threads. With this information, you'll quickly find:
showactstack <activation>
Where <activation> is the thread address (pointer value, not ID), so e.g. showactstack 0xffffff8007acf098.
Note also the following helpful commands:
showtaskstacks <task address>
showtaskstacks -F <taskname>
These show all the stacks corresponding to a task/process.
showallstacks
This prints the kernel stacks for all threads in the system. Be warned: this one can take a while to complete. (IIRC it's faster over Firewire than ethernet kdp, but can still take minutes.)