diff options
| -rw-r--r-- | kernel/printk/printk.c | 83 |
1 files changed, 63 insertions, 20 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index afd926611f0f..578723208f14 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2982,6 +2982,34 @@ 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. + */ +#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 inline void printk_legacy_allow_spinlock_enter(void) +{ + lock_map_acquire_try(&printk_legacy_map); +} + +static inline void printk_legacy_allow_spinlock_exit(void) +{ + lock_map_release(&printk_legacy_map); +} +#endif /* CONFIG_PREEMPT_RT */ + +/* * Used as the printk buffers for non-panic, serialized console printing. * This is for legacy (!CON_NBCON) as well as all boot (CON_BOOT) consoles. * Its usage requires the console_lock held. @@ -3030,31 +3058,46 @@ static bool console_emit_next_record(struct console *con, bool *handover, int co con->dropped = 0; } - /* - * While actively printing out messages, if another printk() - * were to occur on another CPU, it may wait for this one to - * finish. This task can not be preempted if there is a - * waiter waiting to take over. - * - * Interrupts are disabled because the hand over to a waiter - * must not be interrupted until the hand over is completed - * (@console_waiter is cleared). - */ - printk_safe_enter_irqsave(flags); - console_lock_spinning_enable(); + /* Write everything out to the hardware. */ - /* Do not trace print latency. */ - stop_critical_timings(); + if (force_legacy_kthread() && !panic_in_progress()) { + /* + * With forced threading this function is in a task context + * (either legacy kthread or get_init_console_seq()). There + * is no need for concern about printk reentrance, handovers, + * or lockdep complaints. + */ - /* Write everything out to the hardware. */ - con->write(con, outbuf, pmsg.outbuf_len); + con->write(con, outbuf, pmsg.outbuf_len); + con->seq = pmsg.seq + 1; + } else { + /* + * While actively printing out messages, if another printk() + * were to occur on another CPU, it may wait for this one to + * finish. This task can not be preempted if there is a + * waiter waiting to take over. + * + * Interrupts are disabled because the hand over to a waiter + * must not be interrupted until the hand over is completed + * (@console_waiter is cleared). + */ + printk_safe_enter_irqsave(flags); + console_lock_spinning_enable(); - start_critical_timings(); + /* Do not trace print latency. */ + stop_critical_timings(); - con->seq = pmsg.seq + 1; + printk_legacy_allow_spinlock_enter(); + con->write(con, outbuf, pmsg.outbuf_len); + printk_legacy_allow_spinlock_exit(); - *handover = console_lock_spinning_disable_and_check(cookie); - printk_safe_exit_irqrestore(flags); + start_critical_timings(); + + con->seq = pmsg.seq + 1; + + *handover = console_lock_spinning_disable_and_check(cookie); + printk_safe_exit_irqrestore(flags); + } skip: return true; } |