Subject: linux-next: build failure after merge of the tip tree

From: Qi Zheng <[email-masked]>
Date: Mon, 18 Oct 2021 14:45:12 +0800

On 10/18/21 2:23 PM, Stephen Rothwell wrote:
> Hi all,
> 
> After merging the tip tree, today's linux-next build (x86_64 allnoconfig)
> failed like this:
> 
> arch/x86/kernel/process.c: In function '__get_wchan':
> arch/x86/kernel/process.c:950:2: error: implicit declaration of function 'stack_trace_save_tsk' [-Werror=implicit-function-declaration]
>    950 |  stack_trace_save_tsk(p, &entry, 1, 0);
>        |  ^~~~~~~~~~~~~~~~~~~~
> cc1: some warnings being treated as errors
> 
> Caused by commit
> 
>    bc9bbb81730e ("x86: Fix get_wchan() to support the ORC unwinder")
> 
> stack_trace_save_tsk() requires CONFIG_STACKTRACE which is not set for
> this build.

Maybe get_wchan() can be updated to:

unsigned long get_wchan(struct task_struct *p)
{
#ifdef CONFIG_STACKTRACE
	unsigned long entry = 0;

	stack_trace_save_tsk(p, &entry, 1, 0);
	return entry;
#else /* CONFIG_STACKTRACE */
	return 0;
#endif
}

Thanks,
Qi

> 
> I have reverted that commit, and commit
> 
>    42a20f86dc19 ("sched: Add wrapper for get_wchan() to keep task blocked")
> 
> which follows it, for today.
>