diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2025-10-26 16:07:26 +0100 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2025-10-29 14:20:56 +0100 |
| commit | 20793955835fe29a5582f68ff031fdcd35cc98ed (patch) | |
| tree | 289da071586f35a2c38fcfaebe336a1be75a1e4a | |
| parent | daeed1595b4ddf314bad8ee40b2662e03fd012dc (diff) | |
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 <oleg@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20251026150726.GA23223@redhat.com
[pmladek@suse.com: Fixed indentation.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
| -rw-r--r-- | kernel/printk/printk.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 578723208f14..b51ba9f9e79b 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) { |