Avoid deadlocks against rq->lock and xtime_lock by using RCU to defer
the klogd wakeup.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Steven Rostedt <srostedt@redhat.com>
---
diff --git a/kernel/printk.c b/kernel/printk.c
index b51b156..8870c2e 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -32,6 +32,7 @@
#include <linux/security.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>
+#include <linux/rcupdate.h>
#include <asm/uaccess.h>
@@ -982,10 +983,37 @@ int is_console_locked(void)
return console_locked;
}
+struct klogd_wakeup_state {
+ struct rcu_head head;
+ int pending;
+};
+
+DEFINE_PER_CPU(struct klogd_wakeup_state, kws);
+
+void __wake_up_klogd(struct rcu_head *head)
+{
+ struct klogd_wakeup_state *kws =
+ container_of(head, struct klogd_wakeup_state, head);
+
+ wake_up_interruptible(&log_wait);
+ kws->pending = 0;
+}
+
void wake_up_klogd(void)
{
- if (!oops_in_progress && waitqueue_active(&log_wait))
- wake_up_interruptible(&log_wait);
+ unsigned long flags;
+ struct klogd_wakeup_state *kws;
+
+ if (!waitqueue_active(&log_wait))
+ return;
+
+ local_irq_save(flags);
+ kws = &__get_cpu_var(kws);
+ if (!kws->pending) {
+ kws->pending = 1;
+ call_rcu(&kws->head, __wake_up_klogd);
+ }
+ local_irq_restore(flags);
}
/**
--
