Messages in this thread Patch in this message | | | From | Zhen Lei <> | Subject | [PATCH 1/1] ARM: add stacktrace support for non current tasks on SMP | Date | Tue, 19 Sep 2017 20:57:54 +0800 |
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1. An invalid frame.xx can not lead kernel to crash, this should be guaranteed by function unwind_frame itself. Otherwise, walk the stack trace of current is also at risk. 2. There is no way to prevent the walked task becoming rq->curr during walk_stackframe. This means some entries traced maybe inconsistent. But it's better than none. Besides, we can dump it again.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- arch/arm/kernel/stacktrace.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c index 92b7237..80a0e9d 100644 --- a/arch/arm/kernel/stacktrace.c +++ b/arch/arm/kernel/stacktrace.c @@ -120,13 +120,20 @@ static noinline void __save_stack_trace(struct task_struct *tsk, if (tsk != current) { #ifdef CONFIG_SMP /* - * What guarantees do we have here that 'tsk' is not - * running on another CPU? For now, ignore it as we - * can't guarantee we won't explode. + * There is no way to prevent tsk becoming rq->curr during + * walk_stackframe. frame.xx should be sanity checked in + * function unwind_frame. */ - if (trace->nr_entries < trace->max_entries) - trace->entries[trace->nr_entries++] = ULONG_MAX; - return; + if (!task_curr(tsk)) { + frame.fp = thread_saved_fp(tsk); + frame.sp = thread_saved_sp(tsk); + frame.lr = 0; /* recovered from the stack */ + frame.pc = thread_saved_pc(tsk); + } else { + if (trace->nr_entries < trace->max_entries) + trace->entries[trace->nr_entries++] = ULONG_MAX; + return; + } #else frame.fp = thread_saved_fp(tsk); frame.sp = thread_saved_sp(tsk); -- 2.5.0
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