admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

printk_legacy_map: use LD_WAIT_CONFIG instead of LD_WAIT_SLEEP

Browse Source 
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>
This commit is contained in:
Oleg Nesterov
2025-10-26 16:07:26 +01:00
committed by Petr Mladek
parent daeed1595b
commit 2079395583
1 changed files with 7 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
kernel/printk/printk.c
View File

@@ -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)
{