diff options
Diffstat (limited to 'kernel/printk/printk.c')
| -rw-r--r-- | kernel/printk/printk.c | 156 |
1 files changed, 133 insertions, 23 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 72de8cc5a13e..1c3c086bc36c 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -404,6 +404,65 @@ DEFINE_RAW_SPINLOCK(logbuf_lock); printk_safe_exit_irqrestore(flags); \ } while (0) +#ifdef CONFIG_EARLY_PRINTK +struct console *early_console; + +static void early_vprintk(const char *fmt, va_list ap) +{ + if (early_console) { + char buf[512]; + int n = vscnprintf(buf, sizeof(buf), fmt, ap); + + early_console->write(early_console, buf, n); + } +} + +asmlinkage void early_printk(const char *fmt, ...) +{ + va_list ap; + + va_start(ap, fmt); + early_vprintk(fmt, ap); + va_end(ap); +} + +/* + * This is independent of any log levels - a global + * kill switch that turns off all of printk. + * + * Used by the NMI watchdog if early-printk is enabled. + */ +static bool __read_mostly printk_killswitch; + +static int __init force_early_printk_setup(char *str) +{ + printk_killswitch = true; + return 0; +} +early_param("force_early_printk", force_early_printk_setup); + +void printk_kill(void) +{ + printk_killswitch = true; +} + +#ifdef CONFIG_PRINTK +static int forced_early_printk(const char *fmt, va_list ap) +{ + if (!printk_killswitch) + return 0; + early_vprintk(fmt, ap); + return 1; +} +#endif + +#else +static inline int forced_early_printk(const char *fmt, va_list ap) +{ + return 0; +} +#endif + #ifdef CONFIG_PRINTK DECLARE_WAIT_QUEUE_HEAD(log_wait); /* the next printk record to read by syslog(READ) or /proc/kmsg */ @@ -1357,6 +1416,8 @@ static int syslog_print_all(char __user *buf, int size, bool clear) { char *text; int len = 0; + int attempts = 0; + int num_msg; text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); if (!text) @@ -1368,6 +1429,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) u64 seq; u32 idx; +try_again: + attempts++; + if (attempts > 10) { + len = -EBUSY; + goto out; + } + num_msg = 0; + /* * Find first record that fits, including all following records, * into the user-provided buffer for this dump. @@ -1380,6 +1449,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) len += msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; + num_msg++; + if (num_msg > 5) { + num_msg = 0; + logbuf_unlock_irq(); + logbuf_lock_irq(); + if (clear_seq < log_first_seq) + goto try_again; + } } /* move first record forward until length fits into the buffer */ @@ -1391,6 +1468,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) len -= msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; + num_msg++; + if (num_msg > 5) { + num_msg = 0; + logbuf_unlock_irq(); + logbuf_lock_irq(); + if (clear_seq < log_first_seq) + goto try_again; + } } /* last message fitting into this dump */ @@ -1429,6 +1514,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) clear_seq = log_next_seq; clear_idx = log_next_idx; } +out: logbuf_unlock_irq(); kfree(text); @@ -1552,6 +1638,7 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) return do_syslog(type, buf, len, SYSLOG_FROM_READER); } +#ifndef CONFIG_PREEMPT_RT_FULL /* * Special console_lock variants that help to reduce the risk of soft-lockups. * They allow to pass console_lock to another printk() call using a busy wait. @@ -1692,6 +1779,15 @@ static int console_trylock_spinning(void) return 1; } +#else + +static int console_trylock_spinning(void) +{ + return console_trylock(); +} + +#endif + /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. @@ -1707,6 +1803,12 @@ static void call_console_drivers(const char *ext_text, size_t ext_len, if (!console_drivers) return; + if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) { + if (in_irq() || in_nmi()) + return; + } + + migrate_disable(); for_each_console(con) { if (exclusive_console && con != exclusive_console) continue; @@ -1722,6 +1824,7 @@ static void call_console_drivers(const char *ext_text, size_t ext_len, else con->write(con, text, len); } + migrate_enable(); } int printk_delay_msec __read_mostly; @@ -1891,6 +1994,13 @@ asmlinkage int vprintk_emit(int facility, int level, bool in_sched = false; unsigned long flags; + /* + * Fall back to early_printk if a debugging subsystem has + * killed printk output + */ + if (unlikely(forced_early_printk(fmt, args))) + return 1; + if (level == LOGLEVEL_SCHED) { level = LOGLEVEL_DEFAULT; in_sched = true; @@ -1906,20 +2016,30 @@ asmlinkage int vprintk_emit(int facility, int level, /* If called from the scheduler, we can not call up(). */ if (!in_sched) { + int may_trylock = 1; + +#ifdef CONFIG_PREEMPT_RT_FULL + /* + * we can't take a sleeping lock with IRQs or preeption disabled + * so we can't print in these contexts + */ + if (!(preempt_count() == 0 && !irqs_disabled())) + may_trylock = 0; +#endif /* * Disable preemption to avoid being preempted while holding * console_sem which would prevent anyone from printing to * console */ - preempt_disable(); + migrate_disable(); /* * Try to acquire and then immediately release the console * semaphore. The release will print out buffers and wake up * /dev/kmsg and syslog() users. */ - if (console_trylock_spinning()) + if (may_trylock && console_trylock_spinning()) console_unlock(); - preempt_enable(); + migrate_enable(); } wake_up_klogd(); @@ -2031,26 +2151,6 @@ static bool suppress_message_printing(int level) { return false; } #endif /* CONFIG_PRINTK */ -#ifdef CONFIG_EARLY_PRINTK -struct console *early_console; - -asmlinkage __visible void early_printk(const char *fmt, ...) -{ - va_list ap; - char buf[512]; - int n; - - if (!early_console) - return; - - va_start(ap, fmt); - n = vscnprintf(buf, sizeof(buf), fmt, ap); - va_end(ap); - - early_console->write(early_console, buf, n); -} -#endif - static int __add_preferred_console(char *name, int idx, char *options, char *brl_options) { @@ -2391,6 +2491,10 @@ skip: console_seq++; raw_spin_unlock(&logbuf_lock); +#ifdef CONFIG_PREEMPT_RT_FULL + printk_safe_exit_irqrestore(flags); + call_console_drivers(ext_text, ext_len, text, len); +#else /* * While actively printing out messages, if another printk() * were to occur on another CPU, it may wait for this one to @@ -2409,6 +2513,7 @@ skip: } printk_safe_exit_irqrestore(flags); +#endif if (do_cond_resched) cond_resched(); @@ -2460,6 +2565,11 @@ void console_unblank(void) { struct console *c; + if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) { + if (in_irq() || in_nmi()) + return; + } + /* * console_unblank can no longer be called in interrupt context unless * oops_in_progress is set to 1.. |