1 files changed, 41 insertions, 16 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 89011bf8c106..423a8c765a57 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -573,11 +573,6 @@ static int __init printk_time_setup(char *str)
 
 __setup("time", printk_time_setup);
 
-__attribute__((weak)) unsigned long long printk_clock(void)
-{
-        return sched_clock();
-}
-
 /* Check if we have any console registered that can be called early in boot. */
 static int have_callable_console(void)
 {
@@ -628,30 +623,57 @@ asmlinkage int printk(const char *fmt, ...)
 /* cpu currently holding logbuf_lock */
 static volatile unsigned int printk_cpu = UINT_MAX;
 
+const char printk_recursion_bug_msg [] =
+                        KERN_CRIT "BUG: recent printk recursion!\n";
+static int printk_recursion_bug;
+
 asmlinkage int vprintk(const char *fmt, va_list args)
 {
+        static int log_level_unknown = 1;
+        static char printk_buf[1024];
+
         unsigned long flags;
-        int printed_len;
+        int printed_len = 0;
+        int this_cpu;
         char *p;
-        static char printk_buf[1024];
-        static int log_level_unknown = 1;
 
         boot_delay_msec();
 
         preempt_disable();
-        if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
-                /* If a crash is occurring during printk() on this CPU,
-                 * make sure we can't deadlock */
-                zap_locks();
-
         /* This stops the holder of console_sem just where we want him */
         raw_local_irq_save(flags);
+        this_cpu = smp_processor_id();
+
+        /*
+         * Ouch, printk recursed into itself!
+         */
+        if (unlikely(printk_cpu == this_cpu)) {
+                /*
+                 * If a crash is occurring during printk() on this CPU,
+                 * then try to get the crash message out but make sure
+                 * we can't deadlock. Otherwise just return to avoid the
+                 * recursion and return - but flag the recursion so that
+                 * it can be printed at the next appropriate moment:
+                 */
+                if (!oops_in_progress) {
+                        printk_recursion_bug = 1;
+                        goto out_restore_irqs;
+                }
+                zap_locks();
+        }
+
         lockdep_off();
         spin_lock(&logbuf_lock);
-        printk_cpu = smp_processor_id();
+        printk_cpu = this_cpu;
 
+        if (printk_recursion_bug) {
+                printk_recursion_bug = 0;
+                strcpy(printk_buf, printk_recursion_bug_msg);
+                printed_len = sizeof(printk_recursion_bug_msg);
+        }
         /* Emit the output into the temporary buffer */
-        printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
+        printed_len += vscnprintf(printk_buf + printed_len,
+                                  sizeof(printk_buf), fmt, args);
 
         /*
          * Copy the output into log_buf.  If the caller didn't provide
@@ -680,7 +702,9 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                                         loglev_char = default_message_loglevel
                                                 + '0';
                                 }
-                                t = printk_clock();
+                                t = 0;
+                                if (system_state != SYSTEM_BOOTING)
+                                        t = ktime_to_ns(ktime_get());
                                 nanosec_rem = do_div(t, 1000000000);
                                 tlen = sprintf(tbuf,
                                                 "<%c>[%5lu.%06lu] ",
@@ -744,6 +768,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                 printk_cpu = UINT_MAX;
                 spin_unlock(&logbuf_lock);
                 lockdep_on();
+out_restore_irqs:
                 raw_local_irq_restore(flags);
         }