linux-kernel - [PATCH RT 1/2] printk: Enhance the condition check of msleep in pr

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Date:   Fri, 06 Aug 2021 18:47:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        John Kacur <jkacur@...hat.com>, Daniel Wagner <wagi@...om.org>,
        Tom Zanussi <zanussi@...nel.org>,
        "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>,
        Chao Qin <chao.qin@...el.com>, Lili Li <lili.li@...el.com>,
        John Ogness <john.ogness@...utronix.de>
Subject: [PATCH RT 1/2] printk: Enhance the condition check of msleep in pr_flush()

5.10.56-rt49-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

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

[ Upstream commit 83e9288d9c4295d1195e9d780fcbc42c72ba4a83 ]

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 <chao.qin@...el.com>
Signed-off-by: Lili Li <lili.li@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: John Ogness <john.ogness@...utronix.de>
Signed-off-by: John Ogness <john.ogness@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/lkml/20210719022649.3444072-1-chao.qin@intel.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/printk/printk.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f56fd2e34cc7..53d90278494b 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3545,7 +3545,9 @@ 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);
 
-- 
2.30.2