linux-kernel - [PATCH] Support resetting WARN

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Date:   Fri, 20 Oct 2017 10:06:33 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        mpe@...erman.id.au
Subject: [PATCH] Support resetting WARN_ONCE for all architectures

From: Andi Kleen <ak@...ux.intel.com>

Some architectures store the WARN_ONCE state in the flags
field of the bug_entry. Clear that one too when resetting
once state through /sys/kernel/debug/clear_warn_once

Pointed out by Michael Ellerman

Improves the earlier patch that add clear_warn_once.

Cc: mpe@...erman.id.au
v2: Add a missing ifdef CONFIG_MODULES. Thanks 0day!
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 include/linux/bug.h |  5 +++++
 kernel/panic.c      |  1 +
 lib/bug.c           | 23 +++++++++++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/include/linux/bug.h b/include/linux/bug.h
index 5d5554c874fd..b8666ee88086 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -42,6 +42,8 @@ enum bug_trap_type report_bug(unsigned long bug_addr, struct pt_regs *regs);
 /* These are defined by the architecture */
 int is_valid_bugaddr(unsigned long addr);
 
+void generic_bug_clear_once(void);
+
 #else	/* !CONFIG_GENERIC_BUG */
 
 static inline enum bug_trap_type report_bug(unsigned long bug_addr,
@@ -50,6 +52,9 @@ static inline enum bug_trap_type report_bug(unsigned long bug_addr,
 	return BUG_TRAP_TYPE_BUG;
 }
 
+
+static inline void generic_bug_clear_once(void) {}
+
 #endif	/* CONFIG_GENERIC_BUG */
 
 /*
diff --git a/kernel/panic.c b/kernel/panic.c
index 49dbdb231a77..840a98fa4963 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -595,6 +595,7 @@ EXPORT_SYMBOL(warn_slowpath_null);
 
 static int clear_warn_once_set(void *data, u64 val)
 {
+	generic_bug_clear_once();
 	memset(__start_once, 0, __end_once - __start_once);
 	return 0;
 }
diff --git a/lib/bug.c b/lib/bug.c
index a6a1137d06db..2adafcb41d5b 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -195,3 +195,26 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 
 	return BUG_TRAP_TYPE_BUG;
 }
+
+static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
+{
+	struct bug_entry *bug;
+
+	for (bug = start; bug < end; bug++)
+		bug->flags &= ~BUGFLAG_ONCE;
+}
+
+void generic_bug_clear_once(void)
+{
+	struct module *mod;
+
+#ifdef CONFIG_MODULES
+	rcu_read_lock_sched();
+	list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
+		clear_once_table(mod->bug_table,
+				 mod->bug_table + mod->num_bugs);
+	rcu_read_unlock_sched();
+#endif
+
+	clear_once_table(__start___bug_table, __stop___bug_table);
+}
-- 
2.13.6