linux-kernel - [PREEMPT_RT][PATCH] printk: Enhance the condition check of msleep in pr

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Date:   Mon, 19 Jul 2021 10:26:50 +0800
From:   chao.qin@...el.com
To:     linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        bigeasy@...utronix.de, tglx@...utronix.de,
        john.ogness@...utronix.de, rostedt@...dmis.org
Cc:     mgross@...ux.intel.com, paul.mei@...el.com, lili.li@...el.com
Subject: [PREEMPT_RT][PATCH] printk: Enhance the condition check of msleep in pr_flush()

From: Chao Qin <chao.qin@...el.com>

There is msleep in pr_flush(). If call WARN() in the early boot
stage such as in early_initcall, pr_flush() will run into msleep
when process scheduler is not ready yet. And then the system will
sleep forever.

Before the system_state is SYSTEM_RUNNING, make sure DO NOT sleep
in pr_flush().

Fixes: 63cf1e4b564a ("printk: add pr_flush()")

Signed-off-by: Chao Qin <chao.qin@...el.com>
Signed-off-by: Lili Li <lili.li@...el.com>
---
 kernel/printk/printk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 209d2392f0d8..a9b3afbdac39 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3620,7 +3620,8 @@ bool pr_flush(int timeout_ms, bool reset_on_progress)
 	u64 diff;
 	u64 seq;
 
-	may_sleep = (preemptible() && !in_softirq());
+	may_sleep = (preemptible() && !in_softirq()
+			&& (system_state >= SYSTEM_RUNNING));
 
 	seq = prb_next_seq(prb);
 

base-commit: 7e175e6b59975c8901ad370f7818937f68de45c1
-- 
2.25.1