diff options
Diffstat (limited to 'debian/patches-rt/0057-printk-Add-a-printk-kill-switch.patch')
| -rw-r--r-- | debian/patches-rt/0057-printk-Add-a-printk-kill-switch.patch | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/debian/patches-rt/0057-printk-Add-a-printk-kill-switch.patch b/debian/patches-rt/0057-printk-Add-a-printk-kill-switch.patch new file mode 100644 index 000000000..54f3d96d2 --- /dev/null +++ b/debian/patches-rt/0057-printk-Add-a-printk-kill-switch.patch @@ -0,0 +1,174 @@ +From 0450159a3552782546de4c88cbeae98683079ee9 Mon Sep 17 00:00:00 2001 +From: Ingo Molnar <mingo@elte.hu> +Date: Fri, 22 Jul 2011 17:58:40 +0200 +Subject: [PATCH 057/347] printk: Add a printk kill switch +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +Add a prinkt-kill-switch. This is used from (NMI) watchdog to ensure that +it does not dead-lock with the early printk code. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + include/linux/printk.h | 2 ++ + kernel/printk/printk.c | 79 +++++++++++++++++++++++++++++++----------- + kernel/watchdog_hld.c | 10 ++++++ + 3 files changed, 71 insertions(+), 20 deletions(-) + +diff --git a/include/linux/printk.h b/include/linux/printk.h +index 6dd867e39365..b9d050428456 100644 +--- a/include/linux/printk.h ++++ b/include/linux/printk.h +@@ -140,9 +140,11 @@ struct va_format { + #ifdef CONFIG_EARLY_PRINTK + extern asmlinkage __printf(1, 2) + void early_printk(const char *fmt, ...); ++extern void printk_kill(void); + #else + static inline __printf(1, 2) __cold + void early_printk(const char *s, ...) { } ++static inline void printk_kill(void) { } + #endif + + #ifdef CONFIG_PRINTK_NMI +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index 2ba16c426ba5..963c20ab9548 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -407,6 +407,58 @@ 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; ++ ++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 */ +@@ -1935,6 +1987,13 @@ asmlinkage int vprintk_emit(int facility, int level, + unsigned long flags; + u64 curr_log_seq; + ++ /* ++ * 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; +@@ -2079,26 +2138,6 @@ 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) + { +diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c +index 71381168dede..685443375dc0 100644 +--- a/kernel/watchdog_hld.c ++++ b/kernel/watchdog_hld.c +@@ -24,6 +24,8 @@ static DEFINE_PER_CPU(bool, hard_watchdog_warn); + static DEFINE_PER_CPU(bool, watchdog_nmi_touch); + static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); + static DEFINE_PER_CPU(struct perf_event *, dead_event); ++static DEFINE_RAW_SPINLOCK(watchdog_output_lock); ++ + static struct cpumask dead_events_mask; + + static unsigned long hardlockup_allcpu_dumped; +@@ -134,6 +136,13 @@ static void watchdog_overflow_callback(struct perf_event *event, + /* only print hardlockups once */ + if (__this_cpu_read(hard_watchdog_warn) == true) + return; ++ /* ++ * If early-printk is enabled then make sure we do not ++ * lock up in printk() and kill console logging: ++ */ ++ printk_kill(); ++ ++ raw_spin_lock(&watchdog_output_lock); + + pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu); + print_modules(); +@@ -151,6 +160,7 @@ static void watchdog_overflow_callback(struct perf_event *event, + !test_and_set_bit(0, &hardlockup_allcpu_dumped)) + trigger_allbutself_cpu_backtrace(); + ++ raw_spin_unlock(&watchdog_output_lock); + if (hardlockup_panic) + nmi_panic(regs, "Hard LOCKUP"); + +-- +2.36.1 + |