v4.19.13 snapshot.
diff --git a/lib/dump_stack.c b/lib/dump_stack.c
new file mode 100644
index 0000000..5cff72f
--- /dev/null
+++ b/lib/dump_stack.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Provide a default dump_stack() function for architectures
+ * which don't implement their own.
+ */
+
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/smp.h>
+#include <linux/atomic.h>
+#include <linux/kexec.h>
+#include <linux/utsname.h>
+
+static char dump_stack_arch_desc_str[128];
+
+/**
+ * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
+ * @fmt: printf-style format string
+ * @...: arguments for the format string
+ *
+ * The configured string will be printed right after utsname during task
+ * dumps. Usually used to add arch-specific system identifiers. If an
+ * arch wants to make use of such an ID string, it should initialize this
+ * as soon as possible during boot.
+ */
+void __init dump_stack_set_arch_desc(const char *fmt, ...)
+{
+ va_list args;
+
+ va_start(args, fmt);
+ vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
+ fmt, args);
+ va_end(args);
+}
+
+/**
+ * dump_stack_print_info - print generic debug info for dump_stack()
+ * @log_lvl: log level
+ *
+ * Arch-specific dump_stack() implementations can use this function to
+ * print out the same debug information as the generic dump_stack().
+ */
+void dump_stack_print_info(const char *log_lvl)
+{
+ printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s\n",
+ log_lvl, raw_smp_processor_id(), current->pid, current->comm,
+ kexec_crash_loaded() ? "Kdump: loaded " : "",
+ print_tainted(),
+ init_utsname()->release,
+ (int)strcspn(init_utsname()->version, " "),
+ init_utsname()->version);
+
+ if (dump_stack_arch_desc_str[0] != '\0')
+ printk("%sHardware name: %s\n",
+ log_lvl, dump_stack_arch_desc_str);
+
+ print_worker_info(log_lvl, current);
+}
+
+/**
+ * show_regs_print_info - print generic debug info for show_regs()
+ * @log_lvl: log level
+ *
+ * show_regs() implementations can use this function to print out generic
+ * debug information.
+ */
+void show_regs_print_info(const char *log_lvl)
+{
+ dump_stack_print_info(log_lvl);
+}
+
+static void __dump_stack(void)
+{
+ dump_stack_print_info(KERN_DEFAULT);
+ show_stack(NULL, NULL);
+}
+
+/**
+ * dump_stack - dump the current task information and its stack trace
+ *
+ * Architectures can override this implementation by implementing its own.
+ */
+#ifdef CONFIG_SMP
+static atomic_t dump_lock = ATOMIC_INIT(-1);
+
+asmlinkage __visible void dump_stack(void)
+{
+ unsigned long flags;
+ int was_locked;
+ int old;
+ int cpu;
+
+ /*
+ * Permit this cpu to perform nested stack dumps while serialising
+ * against other CPUs
+ */
+retry:
+ local_irq_save(flags);
+ cpu = smp_processor_id();
+ old = atomic_cmpxchg(&dump_lock, -1, cpu);
+ if (old == -1) {
+ was_locked = 0;
+ } else if (old == cpu) {
+ was_locked = 1;
+ } else {
+ local_irq_restore(flags);
+ cpu_relax();
+ goto retry;
+ }
+
+ __dump_stack();
+
+ if (!was_locked)
+ atomic_set(&dump_lock, -1);
+
+ local_irq_restore(flags);
+}
+#else
+asmlinkage __visible void dump_stack(void)
+{
+ __dump_stack();
+}
+#endif
+EXPORT_SYMBOL(dump_stack);