Commit 20793955 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Petr Mladek
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Reviewed-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20251026150726.GA23223@redhat.com


[pmladek@suse.com: Fixed indentation.]
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent daeed159

kernel/printk/printk.c

+7 −10
Original line number Diff line number Diff line
@@ -2982,21 +2982,18 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq, 
}



/*

 * 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)

{