Hello Petr,
On (04/21/16 13:48), Petr Mladek wrote:
> extern void printk_nmi_flush(void);
> +extern void printk_nmi_flush_on_panic(void);
> #else
> static inline void printk_nmi_flush(void) { }
> +static inline void printk_nmi_flush_on_panic(void) { }
[..]
> +void printk_nmi_flush_on_panic(void)
> +{
> + /*
> + * Make sure that we could access the main ring buffer.
> + * Do not risk a double release when more CPUs are up.
> + */
> + if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) {
> + if (num_online_cpus() > 1)
> + return;
> +
> + debug_locks_off();
> + raw_spin_lock_init(&logbuf_lock);
> + }
> +
> + printk_nmi_flush();
> +}
[..]
> -static DEFINE_RAW_SPINLOCK(logbuf_lock);
> +DEFINE_RAW_SPINLOCK(logbuf_lock);
just an idea,
how about doing it a bit differently?
move printk_nmi_flush_on_panic() to printk.c, and place it next to
printk_flush_on_panic() (so we will have two printk "flush-on-panic"
functions sitting together). /* printk_nmi_flush() is in printk.h,
so it's visible to printk anyway */
it also will let us keep logbuf_lock static, it's a bit too internal
to printk to expose it, I think.
IOW, something like this?
---
kernel/printk/internal.h | 2 --
kernel/printk/nmi.c | 27 ---------------------------
kernel/printk/printk.c | 29 ++++++++++++++++++++++++++++-
3 files changed, 28 insertions(+), 30 deletions(-)
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 7fd2838..341bedc 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -22,8 +22,6 @@ int __printf(1, 0) vprintk_default(const char *fmt, va_list args);
#ifdef CONFIG_PRINTK_NMI
-extern raw_spinlock_t logbuf_lock;
-
/*
* printk() could not take logbuf_lock in NMI context. Instead,
* it temporary stores the strings into a per-CPU buffer.
diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c
index b69eb8a..b68a9864 100644
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/nmi.c
@@ -204,33 +204,6 @@ void printk_nmi_flush(void)
__printk_nmi_flush(&per_cpu(nmi_print_seq, cpu).work);
}
-/**
- * printk_nmi_flush_on_panic - flush all per-cpu nmi buffers when the system
- * goes down.
- *
- * Similar to printk_nmi_flush() but it can be called even in NMI context when
- * the system goes down. It does the best effort to get NMI messages into
- * the main ring buffer.
- *
- * Note that it could try harder when there is only one CPU online.
- */
-void printk_nmi_flush_on_panic(void)
-{
- /*
- * Make sure that we could access the main ring buffer.
- * Do not risk a double release when more CPUs are up.
- */
- if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) {
- if (num_online_cpus() > 1)
- return;
-
- debug_locks_off();
- raw_spin_lock_init(&logbuf_lock);
- }
-
- printk_nmi_flush();
-}
-
void __init printk_nmi_init(void)
{
int cpu;
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 0a0e789..1509baa 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -245,7 +245,7 @@ __packed __aligned(4)
* within the scheduler's rq lock. It must be released before calling
* console_unlock() or anything else that might wake up a process.
*/
-DEFINE_RAW_SPINLOCK(logbuf_lock);
+static DEFINE_RAW_SPINLOCK(logbuf_lock);
#ifdef CONFIG_PRINTK
DECLARE_WAIT_QUEUE_HEAD(log_wait);
@@ -2447,6 +2447,33 @@ void console_unblank(void)
}
/**
+ * printk_nmi_flush_on_panic - flush all per-cpu nmi buffers when the system
+ * goes down.
+ *
+ * Similar to printk_nmi_flush() but it can be called even in NMI context when
+ * the system goes down. It does the best effort to get NMI messages into
+ * the main ring buffer.
+ *
+ * Note that it could try harder when there is only one CPU online.
+ */
+void printk_nmi_flush_on_panic(void)
+{
+ /*
+ * Make sure that we could access the main ring buffer.
+ * Do not risk a double release when more CPUs are up.
+ */
+ if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) {
+ if (num_online_cpus() > 1)
+ return;
+
+ debug_locks_off();
+ raw_spin_lock_init(&logbuf_lock);
+ }
+
+ printk_nmi_flush();
+}
+
+/**
* console_flush_on_panic - flush console content on panic
*
* Immediately output all pending messages no matter what.
