linux-kernel - [PATCH 4/5] sched: unset panic_on

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Date:   Fri, 28 Jan 2022 19:42:24 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Baoquan He <bhe@...hat.com>, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>
Cc:     kexec@...ts.infradead.org, linux-doc@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] sched: unset panic_on_warn before calling panic()

As done in the full WARN() handler, panic_on_warn needs to be cleared
before calling panic() to avoid recursive panics.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 kernel/sched/core.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 848eaa0..f5b0886 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5524,8 +5524,17 @@ static noinline void __schedule_bug(struct task_struct *prev)
 		pr_err("Preemption disabled at:");
 		print_ip_sym(KERN_ERR, preempt_disable_ip);
 	}
-	if (panic_on_warn)
+
+	if (panic_on_warn) {
+		/*
+		 * This thread may hit another WARN() in the panic path.
+		 * Resetting this prevents additional WARN() from panicking the
+		 * system on this thread.  Other threads are blocked by the
+		 * panic_mutex in panic().
+		 */
+		panic_on_warn = 0;
 		panic("scheduling while atomic\n");
+	}
 
 	dump_stack();
 	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
-- 
2.1.0