On Fri, 31 May 2019, Petr Mladek wrote:
> WARN_ON_ONCE() could not be called safely under rq lock because
> of console deadlock issues.
>
> It can be simply removed. A better descriptive message is written
> in klp_enable_patch() when klp_have_reliable_stack() fails.
> The remaining debug message is good enough.
>
> Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
> ---
> kernel/livepatch/transition.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index abb2a4a2cbb2..1bf362df76e1 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -247,7 +247,6 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
> int ret, nr_entries;
>
> ret = stack_trace_save_tsk_reliable(task, entries, ARRAY_SIZE(entries));
> - WARN_ON_ONCE(ret == -ENOSYS);
> if (ret < 0) {
> snprintf(err_buf, STACK_ERR_BUF_SIZE,
> "%s: %s:%d has an unreliable stack\n",
The current situation is not the best, but I think the patch improves it
only slightly. I see two possible solutions.
1. we either revert commit 1d98a69e5cef ("livepatch: Remove reliable
stacktrace check in klp_try_switch_task()"), so that klp_check_stack()
returns right away.
2. or we test ret from stack_trace_save_tsk_reliable() for ENOSYS and
return.
In my opinion either of them is better than what we have now (and what we
would have with the patch), because klp_check_stack() returns, but it
prints out that a task has an unreliable stack. Yes, it is pr_debug() only
in the end, but still.
I don't have a preference and my understanding is that Petr does not want
to do v4. I can prepare a patch, but it would be nice to choose now. Josh?
Anyone else?
Miroslav
