[PATCH 3/4] printk, lockdep: Remove lockdep_off() usage

Peter Zijlstra
2011-06-21T15:40:42Z

[-- Attachment #1: printk-remove-lockdep_off.patch --]
[-- Type: text/plain, Size: 2641 bytes --]

Remove the lockdep_off() usage from printk(). Also add a
debug_locks_off() call to zap_locks() since that'll mess up the lock
state in a royal way anyway, and zap_locks() when lockdep causes a
printk() recursion so that we can at observe the splat.

Further switch to local_irq_ ops so that the irq state is properly
tracked (raw_local_irq_* isn't tracked by lockdep, causing confusion).
Also drop superfluous preempt_disable(), disabling IRQs already avoids
scheduling.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/printk.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c
+++ linux-2.6/kernel/printk.c
@@ -686,6 +686,7 @@ static void zap_locks(void)

oops_timestamp = jiffies;

+ debug_locks_off();
/* If a crash is occurring, make sure we can't deadlock */
spin_lock_init(&logbuf_lock);
/* And make sure that we print immediately */
@@ -838,9 +839,8 @@ asmlinkage int vprintk(const char *fmt,
boot_delay_msec();
printk_delay();

- preempt_disable();
/* This stops the holder of console_sem just where we want him */
- raw_local_irq_save(flags);
+ local_irq_save(flags);
this_cpu = smp_processor_id();

/*
@@ -854,14 +854,13 @@ asmlinkage int vprintk(const char *fmt,
* recursion and return - but flag the recursion so that
* it can be printed at the next appropriate moment:
*/
- if (!oops_in_progress) {
+ if (!oops_in_progress && !lockdep_recursing(current)) {
recursion_bug = 1;
goto out_restore_irqs;
}
zap_locks();
}

- lockdep_off();
spin_lock(&logbuf_lock);
printk_cpu = this_cpu;

@@ -958,11 +957,9 @@ asmlinkage int vprintk(const char *fmt,
if (console_trylock_for_printk(this_cpu))
console_unlock();

- lockdep_on();
out_restore_irqs:
- raw_local_irq_restore(flags);
+ local_irq_restore(flags);

- preempt_enable();
return printed_len;
}
EXPORT_SYMBOL(printk);
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index ef820a3..132d210 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -343,6 +343,8 @@ extern void lockdep_trace_alloc(gfp_t mask);

#define lockdep_assert_held(l) WARN_ON(debug_locks && !lockdep_is_held(l))

+#define lockdep_recursing(tsk) ((tsk)->lockdep_recursion)
+
#else /* !LOCKDEP */

static inline void lockdep_off(void)
@@ -392,6 +394,8 @@ struct lock_class_key { };

#define lockdep_assert_held(l) do { } while (0)

+#define lockdep_recursing(tsk) (0)
+
#endif /* !LOCKDEP */

#ifdef CONFIG_LOCK_STAT