// SPDX-License-Identifier: GPL-2.0-only/* * linux/kernel/panic.c * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * This function is used through-out the kernel (including mm and fs) * to indicate a major problem. */#include <linux/debug_locks.h>#include <linux/sched/debug.h>#include <linux/interrupt.h>#include <linux/kgdb.h>#include <linux/kmsg_dump.h>#include <linux/kallsyms.h>#include <linux/notifier.h>#include <linux/vt_kern.h>#include <linux/module.h>#include <linux/random.h>#include <linux/ftrace.h>#include <linux/reboot.h>#include <linux/delay.h>#include <linux/kexec.h>#include <linux/panic_notifier.h>#include <linux/sched.h>#include <linux/string_helpers.h>#include <linux/sysrq.h>#include <linux/init.h>#include <linux/nmi.h>#include <linux/console.h>#include <linux/bug.h>#include <linux/ratelimit.h>#include <linux/debugfs.h>#include <linux/sysfs.h>#include <linux/context_tracking.h>#include <linux/seq_buf.h>#include <linux/sys_info.h>#include <trace/events/error_report.h>#include <asm/sections.h> #define PANIC_TIMER_STEP 100#define PANIC_BLINK_SPD 18 #ifdef CONFIG_SMP/* * Should we dump all CPUs backtraces in an oops event? * Defaults to 0, can be changed via sysctl. */static unsigned int __read_mostly sysctl_oops_all_cpu_backtrace;#else#define sysctl_oops_all_cpu_backtrace 0#endif /* CONFIG_SMP */ int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;static unsigned long tainted_mask = IS_ENABLED(CONFIG_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0;static int pause_on_oops;static int pause_on_oops_flag;static DEFINE_SPINLOCK(pause_on_oops_lock);bool crash_kexec_post_notifiers;int panic_on_warn __read_mostly;unsigned long panic_on_taint;bool panic_on_taint_nousertaint = false;static unsigned int warn_limit __read_mostly;static bool panic_console_replay; bool panic_triggering_all_cpu_backtrace; int panic_timeout = CONFIG_PANIC_TIMEOUT;EXPORT_SYMBOL_GPL(panic_timeout); unsigned long panic_print; ATOMIC_NOTIFIER_HEAD(panic_notifier_list); EXPORT_SYMBOL(panic_notifier_list); #ifdef CONFIG_SYSCTL /* * Taint values can only be increased * This means we can safely use a temporary. */static int proc_taint(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos){ struct ctl_table t; unsigned long tmptaint = get_taint(); int err; if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; t = *table; t.data = &tmptaint; err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; if (write) { int i; /* * If we are relying on panic_on_taint not producing * false positives due to userspace input, bail out * before setting the requested taint flags. */ if (panic_on_taint_nousertaint && (tmptaint & panic_on_taint)) return -EINVAL; /* * Poor man's atomic or. Not worth adding a primitive * to everyone's atomic.h for this */ for (i = 0; i < TAINT_FLAGS_COUNT; i++) if ((1UL << i) & tmptaint) add_taint(i, LOCKDEP_STILL_OK); } return err;} static int sysctl_panic_print_handler(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos){ pr_info_once("Kernel: 'panic_print' sysctl interface will be obsoleted by both 'panic_sys_info' and 'panic_console_replay'\n"); return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);} static const struct ctl_table kern_panic_table[] = {#ifdef CONFIG_SMP { .procname = "oops_all_cpu_backtrace", .data = &sysctl_oops_all_cpu_backtrace, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, },#endif { .procname = "tainted", .maxlen = sizeof(long), .mode = 0644, .proc_handler = proc_taint, }, { .procname = "panic", .data = &panic_timeout, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, }, { .procname = "panic_on_oops", .data = &panic_on_oops, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, }, { .procname = "panic_print", .data = &panic_print, .maxlen = sizeof(unsigned long), .mode = 0644, .proc_handler = sysctl_panic_print_handler, }, { .procname = "panic_on_warn", .data = &panic_on_warn, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, }, { .procname = "warn_limit", .data = &warn_limit, .maxlen = sizeof(warn_limit), .mode = 0644, .proc_handler = proc_douintvec, },#if (defined(CONFIG_X86_32) || defined(CONFIG_PARISC)) && \ defined(CONFIG_DEBUG_STACKOVERFLOW) { .procname = "panic_on_stackoverflow", .data = &sysctl_panic_on_stackoverflow, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, },#endif { .procname = "panic_sys_info", .data = &panic_print, .maxlen = sizeof(panic_print), .mode = 0644, .proc_handler = sysctl_sys_info_handler, },}; static __init int kernel_panic_sysctls_init(void){ register_sysctl_init("kernel", kern_panic_table); return 0;}late_initcall(kernel_panic_sysctls_init);#endif /* The format is "panic_sys_info=tasks,mem,locks,ftrace,..." */static int __init setup_panic_sys_info(char *buf){ /* There is no risk of race in kernel boot phase */ panic_print = sys_info_parse_param(buf); return 1;}__setup("panic_sys_info=", setup_panic_sys_info); static atomic_t warn_count = ATOMIC_INIT(0); #ifdef CONFIG_SYSFSstatic ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr, char *page){ return sysfs_emit(page, "%d\n", atomic_read(&warn_count));} static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count); static __init int kernel_panic_sysfs_init(void){ sysfs_add_file_to_group(kernel_kobj, &warn_count_attr.attr, NULL); return 0;}late_initcall(kernel_panic_sysfs_init);#endif static long no_blink(int state){ return 0;} /* Returns how long it waited in ms */long (*panic_blink)(int state);EXPORT_SYMBOL(panic_blink); /* * Stop ourself in panic -- architecture code may override this */void __weak __noreturn panic_smp_self_stop(void){ while (1) cpu_relax();} /* * Stop ourselves in NMI context if another CPU has already panicked. Arch code * may override this to prepare for crash dumping, e.g. save regs info. */void __weak __noreturn nmi_panic_self_stop(struct pt_regs *regs){ panic_smp_self_stop();} /* * Stop other CPUs in panic. Architecture dependent code may override this * with more suitable version. For example, if the architecture supports * crash dump, it should save registers of each stopped CPU and disable * per-CPU features such as virtualization extensions. */void __weak crash_smp_send_stop(void){ static int cpus_stopped; /* * This function can be called twice in panic path, but obviously * we execute this only once. */ if (cpus_stopped) return; /* * Note smp_send_stop is the usual smp shutdown function, which * unfortunately means it may not be hardened to work in a panic * situation. */ smp_send_stop(); cpus_stopped = 1;} atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID); /* * A variant of panic() called from NMI context. We return if we've already * panicked on this CPU. If another CPU already panicked, loop in * nmi_panic_self_stop() which can provide architecture dependent code such * as saving register state for crash dump. */void nmi_panic(struct pt_regs *regs, const char *msg){ int old_cpu, this_cpu; old_cpu = PANIC_CPU_INVALID; this_cpu = raw_smp_processor_id(); /* atomic_try_cmpxchg updates old_cpu on failure */ if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) panic("%s", msg); else if (old_cpu != this_cpu) nmi_panic_self_stop(regs);}EXPORT_SYMBOL(nmi_panic); void check_panic_on_warn(const char *origin){ unsigned int limit; if (panic_on_warn) panic("%s: panic_on_warn set ...\n", origin); limit = READ_ONCE(warn_limit); if (atomic_inc_return(&warn_count) >= limit && limit) panic("%s: system warned too often (kernel.warn_limit is %d)", origin, limit);} /* * Helper that triggers the NMI backtrace (if set in panic_print) * and then performs the secondary CPUs shutdown - we cannot have * the NMI backtrace after the CPUs are off! */static void panic_other_cpus_shutdown(bool crash_kexec){ if (panic_print & SYS_INFO_ALL_CPU_BT) { /* Temporary allow non-panic CPUs to write their backtraces. */ panic_triggering_all_cpu_backtrace = true; trigger_all_cpu_backtrace(); panic_triggering_all_cpu_backtrace = false; } /* * Note that smp_send_stop() is the usual SMP shutdown function, * which unfortunately may not be hardened to work in a panic * situation. If we want to do crash dump after notifier calls * and kmsg_dump, we will need architecture dependent extra * bits in addition to stopping other CPUs, hence we rely on * crash_smp_send_stop() for that. */ if (!crash_kexec) smp_send_stop(); else crash_smp_send_stop();} /** * vpanic - halt the system * @fmt: The text string to print * @args: Arguments for the format string * * Display a message, then perform cleanups. This function never returns. */void vpanic(const char *fmt, va_list args){ static char buf[1024]; long i, i_next = 0, len; int state = 0; int old_cpu, this_cpu; bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers; if (panic_on_warn) { /* * This thread may hit another WARN() in the panic path. * Resetting this prevents additional WARN() from panicking the * system on this thread. Other threads are blocked by the * panic_mutex in panic(). */ panic_on_warn = 0; } /* * Disable local interrupts. This will prevent panic_smp_self_stop * from deadlocking the first cpu that invokes the panic, since * there is nothing to prevent an interrupt handler (that runs * after setting panic_cpu) from invoking panic() again. */ local_irq_disable(); preempt_disable_notrace(); /* * It's possible to come here directly from a panic-assertion and * not have preempt disabled. Some functions called from here want * preempt to be disabled. No point enabling it later though... * * Only one CPU is allowed to execute the panic code from here. For * multiple parallel invocations of panic, all other CPUs either * stop themself or will wait until they are stopped by the 1st CPU * with smp_send_stop(). * * cmpxchg success means this is the 1st CPU which comes here, * so go ahead. * `old_cpu == this_cpu' means we came from nmi_panic() which sets * panic_cpu to this CPU. In this case, this is also the 1st CPU. */ old_cpu = PANIC_CPU_INVALID; this_cpu = raw_smp_processor_id(); /* atomic_try_cmpxchg updates old_cpu on failure */ if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) { /* go ahead */ } else if (old_cpu != this_cpu) panic_smp_self_stop(); console_verbose(); bust_spinlocks(1); len = vscnprintf(buf, sizeof(buf), fmt, args); if (len && buf[len - 1] == '\n') buf[len - 1] = '\0'; pr_emerg("Kernel panic - not syncing: %s\n", buf);#ifdef CONFIG_DEBUG_BUGVERBOSE /* * Avoid nested stack-dumping if a panic occurs during oops processing */ if (!test_taint(TAINT_DIE) && oops_in_progress <= 1) dump_stack();#endif /* * If kgdb is enabled, give it a chance to run before we stop all * the other CPUs or else we won't be able to debug processes left * running on them. */ kgdb_panic(buf); /* * If we have crashed and we have a crash kernel loaded let it handle * everything else. * If we want to run this after calling panic_notifiers, pass * the "crash_kexec_post_notifiers" option to the kernel. * * Bypass the panic_cpu check and call __crash_kexec directly. */ if (!_crash_kexec_post_notifiers) __crash_kexec(NULL); panic_other_cpus_shutdown(_crash_kexec_post_notifiers); printk_legacy_allow_panic_sync(); /* * Run any panic handlers, including those that might need to * add information to the kmsg dump output. */ atomic_notifier_call_chain(&panic_notifier_list, 0, buf); sys_info(panic_print); kmsg_dump_desc(KMSG_DUMP_PANIC, buf); /* * If you doubt kdump always works fine in any situation, * "crash_kexec_post_notifiers" offers you a chance to run * panic_notifiers and dumping kmsg before kdump. * Note: since some panic_notifiers can make crashed kernel * more unstable, it can increase risks of the kdump failure too. * * Bypass the panic_cpu check and call __crash_kexec directly. */ if (_crash_kexec_post_notifiers) __crash_kexec(NULL); console_unblank(); /* * We may have ended up stopping the CPU holding the lock (in * smp_send_stop()) while still having some valuable data in the console * buffer. Try to acquire the lock then release it regardless of the * result. The release will also print the buffers out. Locks debug * should be disabled to avoid reporting bad unlock balance when * panic() is not being callled from OOPS. */ debug_locks_off(); console_flush_on_panic(CONSOLE_FLUSH_PENDING); if ((panic_print & SYS_INFO_PANIC_CONSOLE_REPLAY) || panic_console_replay) console_flush_on_panic(CONSOLE_REPLAY_ALL); if (!panic_blink) panic_blink = no_blink; if (panic_timeout > 0) { /* * Delay timeout seconds before rebooting the machine. * We can't use the "normal" timers since we just panicked.Lines 1–500 of 981. Load more
// SPDX-License-Identifier: GPL-2.0-only /* * linux/kernel/panic.c * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * This function is used through-out the kernel (including mm and fs) * to indicate a major problem. */ #include <linux/debug_locks.h> #include <linux/sched/debug.h> #include <linux/interrupt.h> #include <linux/kgdb.h> #include <linux/kmsg_dump.h> #include <linux/kallsyms.h> #include <linux/notifier.h> #include <linux/vt_kern.h> #include <linux/module.h> #include <linux/random.h> #include <linux/ftrace.h> #include <linux/reboot.h> #include <linux/delay.h> #include <linux/kexec.h> #include <linux/panic_notifier.h> #include <linux/sched.h> #include <linux/string_helpers.h> #include <linux/sysrq.h> #include <linux/init.h> #include <linux/nmi.h> #include <linux/console.h> #include <linux/bug.h> #include <linux/ratelimit.h> #include <linux/debugfs.h> #include <linux/sysfs.h> #include <linux/context_tracking.h> #include <linux/seq_buf.h> #include <linux/sys_info.h> #include <trace/events/error_report.h> #include <asm/sections.h> #define PANIC_TIMER_STEP 100 #define PANIC_BLINK_SPD 18 #ifdef CONFIG_SMP /* * Should we dump all CPUs backtraces in an oops event? * Defaults to 0, can be changed via sysctl. */ static unsigned int __read_mostly sysctl_oops_all_cpu_backtrace; #else #define sysctl_oops_all_cpu_backtrace 0 #endif /* CONFIG_SMP */ int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE; static unsigned long tainted_mask = IS_ENABLED(CONFIG_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0; static int pause_on_oops; static int pause_on_oops_flag; static DEFINE_SPINLOCK(pause_on_oops_lock); bool crash_kexec_post_notifiers; int panic_on_warn __read_mostly; unsigned long panic_on_taint; bool panic_on_taint_nousertaint = false; static unsigned int warn_limit __read_mostly; static bool panic_console_replay; bool panic_triggering_all_cpu_backtrace; int panic_timeout = CONFIG_PANIC_TIMEOUT; EXPORT_SYMBOL_GPL(panic_timeout); unsigned long panic_print; ATOMIC_NOTIFIER_HEAD(panic_notifier_list); EXPORT_SYMBOL(panic_notifier_list); #ifdef CONFIG_SYSCTL /* * Taint values can only be increased * This means we can safely use a temporary. */ static int proc_taint(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; unsigned long tmptaint = get_taint(); int err; if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; t = *table; t.data = &tmptaint; err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; if (write) { int i; /* * If we are relying on panic_on_taint not producing * false positives due to userspace input, bail out * before setting the requested taint flags. */ if (panic_on_taint_nousertaint && (tmptaint & panic_on_taint)) return -EINVAL; /* * Poor man's atomic or. Not worth adding a primitive * to everyone's atomic.h for this */ for (i = 0; i < TAINT_FLAGS_COUNT; i++) if ((1UL << i) & tmptaint) add_taint(i, LOCKDEP_STILL_OK); } return err; } static int sysctl_panic_print_handler(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { pr_info_once("Kernel: 'panic_print' sysctl interface will be obsoleted by both 'panic_sys_info' and 'panic_console_replay'\n"); return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); } static const struct ctl_table kern_panic_table[] = { #ifdef CONFIG_SMP { .procname = "oops_all_cpu_backtrace", .data = &sysctl_oops_all_cpu_backtrace, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, }, #endif { .procname = "tainted", .maxlen = sizeof(long), .mode = 0644, .proc_handler = proc_taint, }, { .procname = "panic", .data = &panic_timeout, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, }, { .procname = "panic_on_oops", .data = &panic_on_oops, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, }, { .procname = "panic_print", .data = &panic_print, .maxlen = sizeof(unsigned long), .mode = 0644, .proc_handler = sysctl_panic_print_handler, }, { .procname = "panic_on_warn", .data = &panic_on_warn, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, }, { .procname = "warn_limit", .data = &warn_limit, .maxlen = sizeof(warn_limit), .mode = 0644, .proc_handler = proc_douintvec, }, #if (defined(CONFIG_X86_32) || defined(CONFIG_PARISC)) && \ defined(CONFIG_DEBUG_STACKOVERFLOW) { .procname = "panic_on_stackoverflow", .data = &sysctl_panic_on_stackoverflow, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, }, #endif { .procname = "panic_sys_info", .data = &panic_print, .maxlen = sizeof(panic_print), .mode = 0644, .proc_handler = sysctl_sys_info_handler, }, }; static __init int kernel_panic_sysctls_init(void) { register_sysctl_init("kernel", kern_panic_table); return 0; } late_initcall(kernel_panic_sysctls_init); #endif /* The format is "panic_sys_info=tasks,mem,locks,ftrace,..." */ static int __init setup_panic_sys_info(char *buf) { /* There is no risk of race in kernel boot phase */ panic_print = sys_info_parse_param(buf); return 1; } __setup("panic_sys_info=", setup_panic_sys_info); static atomic_t warn_count = ATOMIC_INIT(0); #ifdef CONFIG_SYSFS static ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr, char *page) { return sysfs_emit(page, "%d\n", atomic_read(&warn_count)); } static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count); static __init int kernel_panic_sysfs_init(void) { sysfs_add_file_to_group(kernel_kobj, &warn_count_attr.attr, NULL); return 0; } late_initcall(kernel_panic_sysfs_init); #endif static long no_blink(int state) { return 0; } /* Returns how long it waited in ms */ long (*panic_blink)(int state); EXPORT_SYMBOL(panic_blink); /* * Stop ourself in panic -- architecture code may override this */ void __weak __noreturn panic_smp_self_stop(void) { while (1) cpu_relax(); } /* * Stop ourselves in NMI context if another CPU has already panicked. Arch code * may override this to prepare for crash dumping, e.g. save regs info. */ void __weak __noreturn nmi_panic_self_stop(struct pt_regs *regs) { panic_smp_self_stop(); } /* * Stop other CPUs in panic. Architecture dependent code may override this * with more suitable version. For example, if the architecture supports * crash dump, it should save registers of each stopped CPU and disable * per-CPU features such as virtualization extensions. */ void __weak crash_smp_send_stop(void) { static int cpus_stopped; /* * This function can be called twice in panic path, but obviously * we execute this only once. */ if (cpus_stopped) return; /* * Note smp_send_stop is the usual smp shutdown function, which * unfortunately means it may not be hardened to work in a panic * situation. */ smp_send_stop(); cpus_stopped = 1; } atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID); /* * A variant of panic() called from NMI context. We return if we've already * panicked on this CPU. If another CPU already panicked, loop in * nmi_panic_self_stop() which can provide architecture dependent code such * as saving register state for crash dump. */ void nmi_panic(struct pt_regs *regs, const char *msg) { int old_cpu, this_cpu; old_cpu = PANIC_CPU_INVALID; this_cpu = raw_smp_processor_id(); /* atomic_try_cmpxchg updates old_cpu on failure */ if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) panic("%s", msg); else if (old_cpu != this_cpu) nmi_panic_self_stop(regs); } EXPORT_SYMBOL(nmi_panic); void check_panic_on_warn(const char *origin) { unsigned int limit; if (panic_on_warn) panic("%s: panic_on_warn set ...\n", origin); limit = READ_ONCE(warn_limit); if (atomic_inc_return(&warn_count) >= limit && limit) panic("%s: system warned too often (kernel.warn_limit is %d)", origin, limit); } /* * Helper that triggers the NMI backtrace (if set in panic_print) * and then performs the secondary CPUs shutdown - we cannot have * the NMI backtrace after the CPUs are off! */ static void panic_other_cpus_shutdown(bool crash_kexec) { if (panic_print & SYS_INFO_ALL_CPU_BT) { /* Temporary allow non-panic CPUs to write their backtraces. */ panic_triggering_all_cpu_backtrace = true; trigger_all_cpu_backtrace(); panic_triggering_all_cpu_backtrace = false; } /* * Note that smp_send_stop() is the usual SMP shutdown function, * which unfortunately may not be hardened to work in a panic * situation. If we want to do crash dump after notifier calls * and kmsg_dump, we will need architecture dependent extra * bits in addition to stopping other CPUs, hence we rely on * crash_smp_send_stop() for that. */ if (!crash_kexec) smp_send_stop(); else crash_smp_send_stop(); } /** * vpanic - halt the system * @fmt: The text string to print * @args: Arguments for the format string * * Display a message, then perform cleanups. This function never returns. */ void vpanic(const char *fmt, va_list args) { static char buf[1024]; long i, i_next = 0, len; int state = 0; int old_cpu, this_cpu; bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers; if (panic_on_warn) { /* * This thread may hit another WARN() in the panic path. * Resetting this prevents additional WARN() from panicking the * system on this thread. Other threads are blocked by the * panic_mutex in panic(). */ panic_on_warn = 0; } /* * Disable local interrupts. This will prevent panic_smp_self_stop * from deadlocking the first cpu that invokes the panic, since * there is nothing to prevent an interrupt handler (that runs * after setting panic_cpu) from invoking panic() again. */ local_irq_disable(); preempt_disable_notrace(); /* * It's possible to come here directly from a panic-assertion and * not have preempt disabled. Some functions called from here want * preempt to be disabled. No point enabling it later though... * * Only one CPU is allowed to execute the panic code from here. For * multiple parallel invocations of panic, all other CPUs either * stop themself or will wait until they are stopped by the 1st CPU * with smp_send_stop(). * * cmpxchg success means this is the 1st CPU which comes here, * so go ahead. * `old_cpu == this_cpu' means we came from nmi_panic() which sets * panic_cpu to this CPU. In this case, this is also the 1st CPU. */ old_cpu = PANIC_CPU_INVALID; this_cpu = raw_smp_processor_id(); /* atomic_try_cmpxchg updates old_cpu on failure */ if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) { /* go ahead */ } else if (old_cpu != this_cpu) panic_smp_self_stop(); console_verbose(); bust_spinlocks(1); len = vscnprintf(buf, sizeof(buf), fmt, args); if (len && buf[len - 1] == '\n') buf[len - 1] = '\0'; pr_emerg("Kernel panic - not syncing: %s\n", buf); #ifdef CONFIG_DEBUG_BUGVERBOSE /* * Avoid nested stack-dumping if a panic occurs during oops processing */ if (!test_taint(TAINT_DIE) && oops_in_progress <= 1) dump_stack(); #endif /* * If kgdb is enabled, give it a chance to run before we stop all * the other CPUs or else we won't be able to debug processes left * running on them. */ kgdb_panic(buf); /* * If we have crashed and we have a crash kernel loaded let it handle * everything else. * If we want to run this after calling panic_notifiers, pass * the "crash_kexec_post_notifiers" option to the kernel. * * Bypass the panic_cpu check and call __crash_kexec directly. */ if (!_crash_kexec_post_notifiers) __crash_kexec(NULL); panic_other_cpus_shutdown(_crash_kexec_post_notifiers); printk_legacy_allow_panic_sync(); /* * Run any panic handlers, including those that might need to * add information to the kmsg dump output. */ atomic_notifier_call_chain(&panic_notifier_list, 0, buf); sys_info(panic_print); kmsg_dump_desc(KMSG_DUMP_PANIC, buf); /* * If you doubt kdump always works fine in any situation, * "crash_kexec_post_notifiers" offers you a chance to run * panic_notifiers and dumping kmsg before kdump. * Note: since some panic_notifiers can make crashed kernel * more unstable, it can increase risks of the kdump failure too. * * Bypass the panic_cpu check and call __crash_kexec directly. */ if (_crash_kexec_post_notifiers) __crash_kexec(NULL); console_unblank(); /* * We may have ended up stopping the CPU holding the lock (in * smp_send_stop()) while still having some valuable data in the console * buffer. Try to acquire the lock then release it regardless of the * result. The release will also print the buffers out. Locks debug * should be disabled to avoid reporting bad unlock balance when * panic() is not being callled from OOPS. */ debug_locks_off(); console_flush_on_panic(CONSOLE_FLUSH_PENDING); if ((panic_print & SYS_INFO_PANIC_CONSOLE_REPLAY) || panic_console_replay) console_flush_on_panic(CONSOLE_REPLAY_ALL); if (!panic_blink) panic_blink = no_blink; if (panic_timeout > 0) { /* * Delay timeout seconds before rebooting the machine. * We can't use the "normal" timers since we just panicked.