Commit 9bbd4c56 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas
Browse files

arm64: prep stack walkers for THREAD_INFO_IN_TASK

When CONFIG_THREAD_INFO_IN_TASK is selected, task stacks may be freed
before a task is destroyed. To account for this, the stacks are
refcounted, and when manipulating the stack of another task, it is
necessary to get/put the stack to ensure it isn't freed and/or re-used
while we do so.

This patch reworks the arm64 stack walking code to account for this.
When CONFIG_THREAD_INFO_IN_TASK is not selected these perform no
refcounting, and this should only be a structural change that does not
affect behaviour.
Signed-off-by: default avatarMark Rutland <>
Tested-by: default avatarLaura Abbott <>
Cc: AKASHI Takahiro <>
Cc: Andy Lutomirski <>
Cc: James Morse <>
Cc: Will Deacon <>
Signed-off-by: default avatarCatalin Marinas <>
parent 2020a5ae
......@@ -350,27 +350,35 @@ struct task_struct *__switch_to(struct task_struct *prev,
unsigned long get_wchan(struct task_struct *p)
struct stackframe frame;
unsigned long stack_page;
unsigned long stack_page, ret = 0;
int count = 0;
if (!p || p == current || p->state == TASK_RUNNING)
return 0;
stack_page = (unsigned long)try_get_task_stack(p);
if (!stack_page)
return 0;
frame.fp = thread_saved_fp(p);
frame.sp = thread_saved_sp(p);
frame.pc = thread_saved_pc(p);
frame.graph = p->curr_ret_stack;
stack_page = (unsigned long)task_stack_page(p);
do {
if (frame.sp < stack_page ||
frame.sp >= stack_page + THREAD_SIZE ||
unwind_frame(p, &frame))
return 0;
if (!in_sched_functions(frame.pc))
return frame.pc;
goto out;
if (!in_sched_functions(frame.pc)) {
ret = frame.pc;
goto out;
} while (count ++ < 16);
return 0;
return ret;
unsigned long arch_align_stack(unsigned long sp)
......@@ -181,6 +181,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
struct stack_trace_data data;
struct stackframe frame;
if (!try_get_task_stack(tsk))
data.trace = trace;
data.skip = trace->skip;
......@@ -202,6 +205,8 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
walk_stackframe(tsk, &frame, save_trace, &data);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
void save_stack_trace(struct stack_trace *trace)
......@@ -148,6 +148,9 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
if (!tsk)
tsk = current;
if (!try_get_task_stack(tsk))
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
......@@ -213,6 +216,8 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
stack + sizeof(struct pt_regs));
void show_stack(struct task_struct *tsk, unsigned long *sp)
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