On Fri, May 29, 2020 at 06:10:59PM +0800, Wang ShaoBo wrote: > Stack unreliable error is reported by stack_trace_save_tsk_reliable() when trying > to insmod a hot patch for module modification, this results in frequent failures > sometimes. We found this 'unreliable' stack is from task just fork. For livepatch, this shouldn't actually be a failure. The patch will just stay in the transition state until after the fork has completed. Which should happen in a reasonable amount of time, right? > 1) The task was not actually scheduled to excute, at this time UNWIND_HINT_EMPTY in > ret_from_fork() has not reset unwind_hint, it's sp_reg and end field remain default value > and end up throwing an error in unwind_next_frame() when called by arch_stack_walk_reliable(); Yes, this seems to be true for forked-but-not-yet-scheduled tasks. I can look at fixing that. I have some ORC cleanups in progress which are related to UNWIND_HINT_EMPTY and the end of the stack. I can add this issue to the list of improvements. > 2) The task has been scheduled but UNWIND_HINT_REGS not finished, at this time > arch_stack_walk_reliable() terminates it's backtracing loop for pt_regs unknown > and return -EINVAL because it's a user task. Hm, do you see this problem with upstream? It seems like it should work. arch_stack_walk_reliable() has this: /* Success path for user tasks */ if (user_mode(regs)) return 0; Where exactly is the error coming from? -- Josh
