b87f02307d
There are reports that the console kthreads block the global console lock when the system is going down, for example, reboot, panic. First part of the solution was to block kthreads in these problematic system states so they stopped handling newly added messages. Second part of the solution is to wait when for the kthreads when they are actively printing. It solves the problem when a message was printed before the system entered the problematic state and the kthreads managed to step in. A busy waiting has to be used because panic() can be called in any context and in an unknown state of the scheduler. There must be a timeout because the kthread might get stuck or sleeping and never release the lock. The timeout 10s is an arbitrary value inspired by the softlockup timeout. Link: https://lore.kernel.org/r/20220610205038.GA3050413@paulmck-ThinkPad-P17-Gen-1 Link: https://lore.kernel.org/r/CAMdYzYpF4FNTBPZsEFeWRuEwSies36QM_As8osPWZSr2q-viEA@mail.gmail.com Signed-off-by: Petr Mladek <pmladek@suse.com> Tested-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20220615162805.27962-3-pmladek@suse.com
62 lines
1.7 KiB
C
62 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* internal.h - printk internal definitions
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*/
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#include <linux/percpu.h>
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#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
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void __init printk_sysctl_init(void);
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int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
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void *buffer, size_t *lenp, loff_t *ppos);
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#else
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#define printk_sysctl_init() do { } while (0)
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#endif
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#ifdef CONFIG_PRINTK
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/* Flags for a single printk record. */
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enum printk_info_flags {
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LOG_NEWLINE = 2, /* text ended with a newline */
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LOG_CONT = 8, /* text is a fragment of a continuation line */
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};
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extern bool block_console_kthreads;
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__printf(4, 0)
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int vprintk_store(int facility, int level,
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const struct dev_printk_info *dev_info,
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const char *fmt, va_list args);
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__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
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__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
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bool printk_percpu_data_ready(void);
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#define printk_safe_enter_irqsave(flags) \
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do { \
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local_irq_save(flags); \
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__printk_safe_enter(); \
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} while (0)
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#define printk_safe_exit_irqrestore(flags) \
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do { \
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__printk_safe_exit(); \
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local_irq_restore(flags); \
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} while (0)
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void defer_console_output(void);
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u16 printk_parse_prefix(const char *text, int *level,
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enum printk_info_flags *flags);
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#else
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/*
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* In !PRINTK builds we still export console_sem
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* semaphore and some of console functions (console_unlock()/etc.), so
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* printk-safe must preserve the existing local IRQ guarantees.
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*/
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#define printk_safe_enter_irqsave(flags) local_irq_save(flags)
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#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
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static inline bool printk_percpu_data_ready(void) { return false; }
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#endif /* CONFIG_PRINTK */
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