linux-kernel - [PATCH v2 27/28] bug: Use RCU instead RCU-sched to protect module_bug

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Message-ID: <20241220174731.514432-28-bigeasy@linutronix.de>
Date: Fri, 20 Dec 2024 18:41:41 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Daniel Gomez <da.gomez@...sung.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v2 27/28] bug: Use RCU instead RCU-sched to protect module_bug_list.

The list module_bug_list relies on module_mutex for writer
synchronisation. The list is already RCU style.
The list removal is synchronized with modules' synchronize_rcu() in
free_module().

Use RCU read lock protection instead of RCU-sched.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 lib/bug.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/lib/bug.c b/lib/bug.c
index e0ff219899902..b1f07459c2ee3 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -66,23 +66,19 @@ static LIST_HEAD(module_bug_list);
 
 static struct bug_entry *module_find_bug(unsigned long bugaddr)
 {
+	struct bug_entry *bug;
 	struct module *mod;
-	struct bug_entry *bug = NULL;
 
-	rcu_read_lock_sched();
+	guard(rcu)();
 	list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
 		unsigned i;
 
 		bug = mod->bug_table;
 		for (i = 0; i < mod->num_bugs; ++i, ++bug)
 			if (bugaddr == bug_addr(bug))
-				goto out;
+				return bug;
 	}
-	bug = NULL;
-out:
-	rcu_read_unlock_sched();
-
-	return bug;
+	return NULL;
 }
 
 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
@@ -235,11 +231,11 @@ void generic_bug_clear_once(void)
 #ifdef CONFIG_MODULES
 	struct module *mod;
 
-	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();
+	scoped_guard(rcu) {
+		list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
+			clear_once_table(mod->bug_table,
+					 mod->bug_table + mod->num_bugs);
+	}
 #endif
 
 	clear_once_table(__start___bug_table, __stop___bug_table);
-- 
2.45.2