nmi_backtrace: add more trigger_*_cpu_backtrace() methods

[cascardo/linux.git] / lib / nmi_backtrace.c

diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 6019c53..df347e3 100644 (file)
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -16,44 +16,25 @@
 #include <linux/delay.h>
 #include <linux/kprobes.h>
 #include <linux/nmi.h>
-#include <linux/seq_buf.h>
 
-#ifdef arch_trigger_all_cpu_backtrace
+#ifdef arch_trigger_cpumask_backtrace
 /* For reliability, we're prepared to waste bits here. */
 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
-static cpumask_t printtrace_mask;
 
-#define NMI_BUF_SIZE           4096
-
-struct nmi_seq_buf {
-       unsigned char           buffer[NMI_BUF_SIZE];
-       struct seq_buf          seq;
-};
-
-/* Safe printing in NMI context */
-static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
-
-/* "in progress" flag of arch_trigger_all_cpu_backtrace */
+/* "in progress" flag of arch_trigger_cpumask_backtrace */
 static unsigned long backtrace_flag;
 
-static void print_seq_line(struct nmi_seq_buf *s, int start, int end)
-{
-       const char *buf = s->buffer + start;
-
-       printk("%.*s", (end - start) + 1, buf);
-}
-
 /*
- * When raise() is called it will be is passed a pointer to the
+ * When raise() is called it will be passed a pointer to the
  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
  * directly from their raise() functions may rely on the mask
  * they are passed being updated as a side effect of this call.
  */
-void nmi_trigger_all_cpu_backtrace(bool include_self,
+void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
+                                  bool exclude_self,
                                   void (*raise)(cpumask_t *mask))
 {
-       struct nmi_seq_buf *s;
-       int i, cpu, this_cpu = get_cpu();
+       int i, this_cpu = get_cpu();
 
        if (test_and_set_bit(0, &backtrace_flag)) {
                /*
@@ -64,24 +45,13 @@ void nmi_trigger_all_cpu_backtrace(bool include_self,
                return;
        }
 
-       cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
-       if (!include_self)
+       cpumask_copy(to_cpumask(backtrace_mask), mask);
+       if (exclude_self)
                cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
 
-       cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask));
-
-       /*
-        * Set up per_cpu seq_buf buffers that the NMIs running on the other
-        * CPUs will write to.
-        */
-       for_each_cpu(cpu, to_cpumask(backtrace_mask)) {
-               s = &per_cpu(nmi_print_seq, cpu);
-               seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE);
-       }
-
        if (!cpumask_empty(to_cpumask(backtrace_mask))) {
-               pr_info("Sending NMI to %s CPUs:\n",
-                       (include_self ? "all" : "other"));
+               pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
+                       this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
                raise(to_cpumask(backtrace_mask));
        }
 
@@ -94,73 +64,25 @@ void nmi_trigger_all_cpu_backtrace(bool include_self,
        }
 
        /*
-        * Now that all the NMIs have triggered, we can dump out their
-        * back traces safely to the console.
+        * Force flush any remote buffers that might be stuck in IRQ context
+        * and therefore could not run their irq_work.
         */
-       for_each_cpu(cpu, &printtrace_mask) {
-               int len, last_i = 0;
+       printk_nmi_flush();
 
-               s = &per_cpu(nmi_print_seq, cpu);
-               len = seq_buf_used(&s->seq);
-               if (!len)
-                       continue;
-
-               /* Print line by line. */
-               for (i = 0; i < len; i++) {
-                       if (s->buffer[i] == '\n') {
-                               print_seq_line(s, last_i, i);
-                               last_i = i + 1;
-                       }
-               }
-               /* Check if there was a partial line. */
-               if (last_i < len) {
-                       print_seq_line(s, last_i, len - 1);
-                       pr_cont("\n");
-               }
-       }
-
-       clear_bit(0, &backtrace_flag);
-       smp_mb__after_atomic();
+       clear_bit_unlock(0, &backtrace_flag);
        put_cpu();
 }
 
-/*
- * It is not safe to call printk() directly from NMI handlers.
- * It may be fine if the NMI detected a lock up and we have no choice
- * but to do so, but doing a NMI on all other CPUs to get a back trace
- * can be done with a sysrq-l. We don't want that to lock up, which
- * can happen if the NMI interrupts a printk in progress.
- *
- * Instead, we redirect the vprintk() to this nmi_vprintk() that writes
- * the content into a per cpu seq_buf buffer. Then when the NMIs are
- * all done, we can safely dump the contents of the seq_buf to a printk()
- * from a non NMI context.
- */
-static int nmi_vprintk(const char *fmt, va_list args)
-{
-       struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
-       unsigned int len = seq_buf_used(&s->seq);
-
-       seq_buf_vprintf(&s->seq, fmt, args);
-       return seq_buf_used(&s->seq) - len;
-}
-
 bool nmi_cpu_backtrace(struct pt_regs *regs)
 {
        int cpu = smp_processor_id();
 
        if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
-               printk_func_t printk_func_save = this_cpu_read(printk_func);
-
-               /* Replace printk to write into the NMI seq */
-               this_cpu_write(printk_func, nmi_vprintk);
                pr_warn("NMI backtrace for cpu %d\n", cpu);
                if (regs)
                        show_regs(regs);
                else
                        dump_stack();
-               this_cpu_write(printk_func, printk_func_save);
-
                cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
                return true;
        }