From: Oleg Nesterov Date: Sun, 26 Oct 2025 15:07:26 +0000 (+0100) Subject: printk_legacy_map: use LD_WAIT_CONFIG instead of LD_WAIT_SLEEP X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=20793955835fe29a5582f68ff031fdcd35cc98ed;p=thirdparty%2Flinux.git printk_legacy_map: use LD_WAIT_CONFIG instead of LD_WAIT_SLEEP printk_legacy_map is used to hide lock nesting violations caused by legacy drivers and is using the wrong override type. LD_WAIT_SLEEP is for always sleeping lock types such as mutex_t. LD_WAIT_CONFIG is for lock type which are sleeping while spinning on PREEMPT_RT such as spinlock_t. Signed-off-by: Oleg Nesterov Reviewed-by: Petr Mladek Reviewed-by: John Ogness Reviewed-by: Sebastian Andrzej Siewior Link: https://patch.msgid.link/20251026150726.GA23223@redhat.com [pmladek@suse.com: Fixed indentation.] Signed-off-by: Petr Mladek --- diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 578723208f141..b51ba9f9e79b8 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2982,21 +2982,18 @@ out: } /* - * Legacy console printing from printk() caller context does not respect - * raw_spinlock/spinlock nesting. For !PREEMPT_RT the lockdep warning is a - * false positive. For PREEMPT_RT the false positive condition does not - * occur. - * - * This map is used to temporarily establish LD_WAIT_SLEEP context for the - * console write() callback when legacy printing to avoid false positive - * lockdep complaints, thus allowing lockdep to continue to function for - * real issues. + * The legacy console always acquires a spinlock_t from its printing + * callback. This violates lock nesting if the caller acquired an always + * spinning lock (raw_spinlock_t) while invoking printk(). This is not a + * problem on PREEMPT_RT because legacy consoles print always from a + * dedicated thread and never from within printk(). Therefore we tell + * lockdep that a sleeping spin lock (spinlock_t) is valid here. */ #ifdef CONFIG_PREEMPT_RT static inline void printk_legacy_allow_spinlock_enter(void) { } static inline void printk_legacy_allow_spinlock_exit(void) { } #else -static DEFINE_WAIT_OVERRIDE_MAP(printk_legacy_map, LD_WAIT_SLEEP); +static DEFINE_WAIT_OVERRIDE_MAP(printk_legacy_map, LD_WAIT_CONFIG); static inline void printk_legacy_allow_spinlock_enter(void) {