hung_task debugging: Print more info when reporting the problem

printk(KERN_ERR) from check_hung_task() likely means we have a bug,
but unlike BUG_ON()/WARN_ON ()it doesn't show the kernel version,
this complicates the bug-reports investigation.

Add the additional pr_err() to print tainted/release/version
like dump_stack_print_info() does, the output becomes:

        INFO: task perl:504 blocked for more than 2 seconds.
	      Not tainted 3.11.0-rc1-10367-g136bb46-dirty #1763
        "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
        ...

While at it, turn the old printk's into pr_err().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: ahecox@redhat.com
Cc: Christopher Williams <cww@redhat.com>
Cc: dwysocha@redhat.com
Cc: gavin@redhat.com
Cc: Mandeep Singh Baines <msb@chromium.org>
Cc: nshi@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20130801165941.GA17544@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 6df614912b9d..3e97fb126e6b 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -15,6 +15,7 @@
 #include <linux/lockdep.h>
 #include <linux/export.h>
 #include <linux/sysctl.h>
+#include <linux/utsname.h>
 
 /*
  * The number of tasks checked:
@@ -99,10 +100,14 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
          * Ok, the task did not get scheduled for more than 2 minutes,
          * complain:
          */
-        printk(KERN_ERR "INFO: task %s:%d blocked for more than "
-                        "%ld seconds.\n", t->comm, t->pid, timeout);
-        printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
-                        " disables this message.\n");
+        pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
+                t->comm, t->pid, timeout);
+        pr_err("      %s %s %.*s\n",
+                print_tainted(), init_utsname()->release,
+                (int)strcspn(init_utsname()->version, " "),
+                init_utsname()->version);
+        pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
+                " disables this message.\n");
         sched_show_task(t);
         debug_show_held_locks(t);