Commit d18bbc21 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

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


kernel/printk/printk.c: revert "printk: enable interrupts before calling console_trylock_for_printk()"

Revert commit 939f04be ("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).

939f04be is modest latency reduction.  Revert it until we understand
the reason for these failures.

Reported-by: default avatarAndreas Bombe <aeb@debian.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e84f1ab3

kernel/printk/printk.c

+18 −26
Original line number Diff line number Diff line
@@ -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;



	if (!in_sched) {

		/*

	 * Disable preemption to avoid being preempted while holding

	 * console_sem which would prevent anyone from printing to console

		 * Try to acquire and then immediately release the console

		 * semaphore.  The release will print out buffers and wake up

		 * /dev/kmsg and syslog() users.

		 */

	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())

		if (console_trylock_for_printk(this_cpu))

			console_unlock();

	preempt_enable();

	}



	lockdep_on();

out_restore_irqs:

	local_irq_restore(flags);

	return printed_len;

}

EXPORT_SYMBOL(vprintk_emit);

CRA Git | Maintained and supported by SUSTech CRA and CCSE