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

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Date:   Tue, 11 Jun 2019 16:13:20 +0200
From:   Miroslav Benes <mbenes@...e.cz>
To:     jpoimboe@...hat.com, jikos@...nel.org, pmladek@...e.com
Cc:     joe.lawrence@...hat.com, kamalesh@...ux.vnet.ibm.com,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH v4 3/3] livepatch: Remove duplicate warning about missing reliable stacktrace support

From: Petr Mladek <pmladek@...e.com>

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 <pmladek@...e.com>
[ mbenes: changelog edited ]
Signed-off-by: Miroslav Benes <mbenes@...e.cz>
---
 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