Subject: printk: Enhance the condition check of msleep in pr_flush()
From: Chao Qin <[email protected]>
Date: Mon Jul 19 10:26:50 2021 +0800

From: Chao Qin <[email protected]>

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: c0b395bd0fe3("printk: add pr_flush()")
Signed-off-by: Chao Qin <[email protected]>
Signed-off-by: Lili Li <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: John Ogness <[email protected]>
Signed-off-by: John Ogness <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]

---
 kernel/printk/printk.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
@ kernel/printk/printk.c:3652 @ bool pr_flush(int timeout_ms, bool reset
 	u64 diff;
 	u64 seq;
 
-	may_sleep = (preemptible() && !in_softirq());
+	may_sleep = (preemptible() &&
+		     !in_softirq() &&
+		     system_state >= SYSTEM_RUNNING);
 
 	seq = prb_next_seq(prb);