From: Jeff Dike The previous get_wchan patch needed some more work. Joe Perches suggested the use of bool where I was using a counter. It also turned out not to work so well on x86_64, so I changed the algorithm a bit. Instead of skipping one frame and looking for the next non-sched symbol, it now looks for at least one scheduler frame, then returns the first symbol seen above that. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton --- arch/um/kernel/process.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff -puN arch/um/kernel/process.c~uml-implement-get_wchan-fix arch/um/kernel/process.c --- a/arch/um/kernel/process.c~uml-implement-get_wchan-fix +++ a/arch/um/kernel/process.c @@ -462,7 +462,8 @@ unsigned long arch_align_stack(unsigned unsigned long get_wchan(struct task_struct *p) { - unsigned long stack_page, sp, ip, count = 0; + unsigned long stack_page, sp, ip; + bool seen_sched = 0; if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING)) return 0; @@ -482,14 +483,11 @@ unsigned long get_wchan(struct task_stru while (sp < stack_page + THREAD_SIZE) { ip = *((unsigned long *) sp); - if (kernel_text_address(ip) && !in_sched_functions(ip)) { - /* - * Skip one valid IP, which will be the low-level UML - * context switcher. - */ - if (count++ == 1) - return ip; - } + if (in_sched_functions(ip)) + /* Ignore everything until we're above the scheduler */ + seen_sched = 1; + else if (kernel_text_address(ip) && seen_sched) + return ip; sp += sizeof(unsigned long); } _