kernel/printk/printk.c: revert "printk: enable interrupts before calling console_tryl...

Revert commit 939f04bec1a4 ("printk: enable interrupts before calling
console_trylock_for_printk()").

Andreas reported:

: None of the post 3.15 kernel boot for me. They all hang at the GRUB
: screen telling me it loaded and started the kernel, but the kernel
: itself stops before it prints anything (or even replaces the GRUB
: background graphics).

939f04bec1a4 is modest latency reduction.  Revert it until we understand
the reason for these failures.

Reported-by: Andreas Bombe <aeb@debian.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ea2d5f6..13e839d 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1416,9 +1416,10 @@ static int have_callable_console(void)
 /*
  * Can we actually use the console at this time on this cpu?
  *
- * Console drivers may assume that per-cpu resources have been allocated. So
- * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
- * call them until this CPU is officially up.
+ * Console drivers may assume that per-cpu resources have
+ * been allocated. So unless they're explicitly marked as
+ * being able to cope (CON_ANYTIME) don't call them until
+ * this CPU is officially up.
  */
 static inline int can_use_console(unsigned int cpu)
 {
@@ -1431,10 +1432,8 @@ static inline int can_use_console(unsigned int cpu)
  * console_lock held, and 'console_locked' set) if it
  * is successful, false otherwise.
  */
-static int console_trylock_for_printk(void)
+static int console_trylock_for_printk(unsigned int cpu)
 {
-       unsigned int cpu = smp_processor_id();
-
        if (!console_trylock())
                return 0;
        /*
@@ -1609,8 +1608,7 @@ asmlinkage int vprintk_emit(int facility, int level,
                 */
                if (!oops_in_progress && !lockdep_recursing(current)) {
                        recursion_bug = 1;
-                       local_irq_restore(flags);
-                       return 0;
+                       goto out_restore_irqs;
                }
                zap_locks();
        }
@@ -1718,27 +1716,21 @@ asmlinkage int vprintk_emit(int facility, int level,
 
        logbuf_cpu = UINT_MAX;
        raw_spin_unlock(&logbuf_lock);
-       lockdep_on();
-       local_irq_restore(flags);
 
        /* If called from the scheduler, we can not call up(). */
-       if (in_sched)
-               return printed_len;
-
-       /*
-        * Disable preemption to avoid being preempted while holding
-        * console_sem which would prevent anyone from printing to console
-        */
-       preempt_disable();
-       /*
-        * Try to acquire and then immediately release the console semaphore.
-        * The release will print out buffers and wake up /dev/kmsg and syslog()
-        * users.
-        */
-       if (console_trylock_for_printk())
-               console_unlock();
-       preempt_enable();
+       if (!in_sched) {
+               /*
+                * Try to acquire and then immediately release the console
+                * semaphore.  The release will print out buffers and wake up
+                * /dev/kmsg and syslog() users.
+                */
+               if (console_trylock_for_printk(this_cpu))
+                       console_unlock();
+       }
 
+       lockdep_on();
+out_restore_irqs:
+       local_irq_restore(flags);
        return printed_len;
 }
 EXPORT_SYMBOL(vprintk_emit);