2019-06-11 14:13:47

by Miroslav Benes

Subject: [PATCH v4 3/3] livepatch: Remove duplicate warning about missing reliable stacktrace support

From: Petr Mladek <[email protected]>

WARN_ON_ONCE() could not be called safely under rq lock because
of console deadlock issues. Moreover WARN_ON_ONCE() is superfluous in
klp_check_stack(), because stack_trace_save_tsk_reliable() cannot return
-ENOSYS thanks to klp_have_reliable_stack() check in
klp_try_switch_task().

Signed-off-by: Petr Mladek <[email protected]>
[ mbenes: changelog edited ]
Signed-off-by: Miroslav Benes <[email protected]>
---
kernel/livepatch/transition.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 7e7ef04689d1..cdf318d86dd6 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",
--
2.21.0

2019-06-12 17:59:26

by Kamalesh Babulal

Subject: Re: [PATCH v4 3/3] livepatch: Remove duplicate warning about missing reliable stacktrace support

On Tue, Jun 11, 2019 at 04:13:20PM +0200, Miroslav Benes wrote:
> From: Petr Mladek <[email protected]>
>
> WARN_ON_ONCE() could not be called safely under rq lock because
> of console deadlock issues. Moreover WARN_ON_ONCE() is superfluous in
> klp_check_stack(), because stack_trace_save_tsk_reliable() cannot return
> -ENOSYS thanks to klp_have_reliable_stack() check in
> klp_try_switch_task().
>
> Signed-off-by: Petr Mladek <[email protected]>
> [ mbenes: changelog edited ]
> Signed-off-by: Miroslav Benes <[email protected]>

Reviewed-by: Kamalesh Babulal <[email protected]>