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Subject[GIT PULL] core/printk changes for v3.1
Linus,

Please pull the latest core-printk-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-printk-for-linus

( These are just the tested-safe commits - the ones that were causing
problems are not included. )

Thanks,

Ingo

------------------>
Peter Zijlstra (3):
printk: Release console_sem after logbuf_lock
printk: Fix console_sem vs logbuf_lock unlock race
lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion

kernel/lockdep.c | 30 ++++++++++++++++++++----------
kernel/printk.c | 24 +++++++++++++++++++++---
2 files changed, 41 insertions(+), 13 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 63437d0..81968a0 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2478,15 +2478,10 @@ mark_held_locks(struct task_struct *curr, enum mark_type mark)
/*
* Hardirqs will be enabled:
*/
-void trace_hardirqs_on_caller(unsigned long ip)
+static void __trace_hardirqs_on_caller(unsigned long ip)
{
struct task_struct *curr = current;

- time_hardirqs_on(CALLER_ADDR0, ip);
-
- if (unlikely(!debug_locks || current->lockdep_recursion))
- return;
-
if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
return;

@@ -2502,8 +2497,6 @@ void trace_hardirqs_on_caller(unsigned long ip)
/* we'll do an OFF -> ON transition: */
curr->hardirqs_enabled = 1;

- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return;
if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
return;
/*
@@ -2525,6 +2518,21 @@ void trace_hardirqs_on_caller(unsigned long ip)
curr->hardirq_enable_event = ++curr->irq_events;
debug_atomic_inc(hardirqs_on_events);
}
+
+void trace_hardirqs_on_caller(unsigned long ip)
+{
+ time_hardirqs_on(CALLER_ADDR0, ip);
+
+ if (unlikely(!debug_locks || current->lockdep_recursion))
+ return;
+
+ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+ return;
+
+ current->lockdep_recursion = 1;
+ __trace_hardirqs_on_caller(ip);
+ current->lockdep_recursion = 0;
+}
EXPORT_SYMBOL(trace_hardirqs_on_caller);

void trace_hardirqs_on(void)
@@ -2574,7 +2582,7 @@ void trace_softirqs_on(unsigned long ip)
{
struct task_struct *curr = current;

- if (unlikely(!debug_locks))
+ if (unlikely(!debug_locks || current->lockdep_recursion))
return;

if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
@@ -2585,6 +2593,7 @@ void trace_softirqs_on(unsigned long ip)
return;
}

+ current->lockdep_recursion = 1;
/*
* We'll do an OFF -> ON transition:
*/
@@ -2599,6 +2608,7 @@ void trace_softirqs_on(unsigned long ip)
*/
if (curr->hardirqs_enabled)
mark_held_locks(curr, SOFTIRQ);
+ current->lockdep_recursion = 0;
}

/*
@@ -2608,7 +2618,7 @@ void trace_softirqs_off(unsigned long ip)
{
struct task_struct *curr = current;

- if (unlikely(!debug_locks))
+ if (unlikely(!debug_locks || current->lockdep_recursion))
return;

if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
diff --git a/kernel/printk.c b/kernel/printk.c
index 3518539..37dff34 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -782,7 +782,7 @@ static inline int can_use_console(unsigned int cpu)
static int console_trylock_for_printk(unsigned int cpu)
__releases(&logbuf_lock)
{
- int retval = 0;
+ int retval = 0, wake = 0;

if (console_trylock()) {
retval = 1;
@@ -795,12 +795,14 @@ static int console_trylock_for_printk(unsigned int cpu)
*/
if (!can_use_console(cpu)) {
console_locked = 0;
- up(&console_sem);
+ wake = 1;
retval = 0;
}
}
printk_cpu = UINT_MAX;
spin_unlock(&logbuf_lock);
+ if (wake)
+ up(&console_sem);
return retval;
}
static const char recursion_bug_msg [] =
@@ -1242,7 +1244,7 @@ void console_unlock(void)
{
unsigned long flags;
unsigned _con_start, _log_end;
- unsigned wake_klogd = 0;
+ unsigned wake_klogd = 0, retry = 0;

if (console_suspended) {
up(&console_sem);
@@ -1251,6 +1253,7 @@ void console_unlock(void)

console_may_schedule = 0;

+again:
for ( ; ; ) {
spin_lock_irqsave(&logbuf_lock, flags);
wake_klogd |= log_start - log_end;
@@ -1271,8 +1274,23 @@ void console_unlock(void)
if (unlikely(exclusive_console))
exclusive_console = NULL;

+ spin_unlock(&logbuf_lock);
+
up(&console_sem);
+
+ /*
+ * Someone could have filled up the buffer again, so re-check if there's
+ * something to flush. In case we cannot trylock the console_sem again,
+ * there's a new owner and the console_unlock() from them will do the
+ * flush, no worries.
+ */
+ spin_lock(&logbuf_lock);
+ if (con_start != log_end)
+ retry = 1;
spin_unlock_irqrestore(&logbuf_lock, flags);
+ if (retry && console_trylock())
+ goto again;
+
if (wake_klogd)
wake_up_klogd();
}

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