linux-kernel - [PATCH v2 3/5] panic: unset panic_on

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Date:   Tue,  8 Feb 2022 20:51:04 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Baoquan He <bhe@...hat.com>, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:     Xuefeng Li <lixuefeng@...ngson.cn>, kexec@...ts.infradead.org,
        linux-doc@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/5] panic: unset panic_on_warn inside panic()

In the current code, the following three places need to unset
panic_on_warn before calling panic() to avoid recursive panics:

kernel/kcsan/report.c: print_report()
kernel/sched/core.c: __schedule_bug()
mm/kfence/report.c: kfence_report_error()

In order to avoid copy-pasting "panic_on_warn = 0" all over the
places, it is better to move it inside panic() and then remove
it from the other places.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 kernel/panic.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index 55b50e0..95ba825 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -185,6 +185,16 @@ void panic(const char *fmt, ...)
 	int old_cpu, this_cpu;
 	bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
 
+	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;
+	}
+
 	/*
 	 * Disable local interrupts. This will prevent panic_smp_self_stop
 	 * from deadlocking the first cpu that invokes the panic, since
@@ -576,16 +586,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 	if (regs)
 		show_regs(regs);
 
-	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;
+	if (panic_on_warn)
 		panic("panic_on_warn set ...\n");
-	}
 
 	if (!regs)
 		dump_stack();
-- 
2.1.0