Commit c1127465 authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
Browse files

uml: implement get_wchan

Implement get_wchan - the algorithm is similar to x86.  It starts with the
stack pointer of the process in question and looks above that for addresses
that are kernel text.  The second one which isn't in the scheduler is the one
that's returned.  The first one is ignored because that will be UML's own
context switching routine.
Signed-off-by: default avatarJeff Dike <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent c9a3072d
......@@ -459,3 +459,38 @@ unsigned long arch_align_stack(unsigned long sp)
return sp & ~0xf;
unsigned long get_wchan(struct task_struct *p)
unsigned long stack_page, sp, ip;
bool seen_sched = 0;
if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
return 0;
stack_page = (unsigned long) task_stack_page(p);
/* Bail if the process has no kernel stack for some reason */
if (stack_page == 0)
return 0;
sp = p->thread.switch_buf->JB_SP;
* Bail if the stack pointer is below the bottom of the kernel
* stack for some reason
if (sp < stack_page)
return 0;
while (sp < stack_page + THREAD_SIZE) {
ip = *((unsigned long *) sp);
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);
return 0;
......@@ -128,6 +128,6 @@ extern struct cpuinfo_um cpu_data[];
#define KSTK_REG(tsk, reg) get_thread_reg(reg, &tsk->thread.switch_buf)
#define get_wchan(p) (0)
extern unsigned long get_wchan(struct task_struct *p);
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